The sequence of next and previous values may not correctly appear in a ComboBox control that is bound to a table field in Visual Studio .NET or in Visual Studio 2005 (894501)


The information in this article applies to:

  • Microsoft Visual Studio .NET (2003), Professional Edition
  • Microsoft Visual Studio .NET (2003), Enterprise Architect Edition
  • Microsoft Visual Studio .NET (2003), Enterprise Developer Edition
  • Microsoft Visual Studio .NET (2002), Professional Edition
  • Microsoft Visual Studio .NET (2002), Enterprise Architect Edition
  • Microsoft Visual Studio .NET (2002), Enterprise Developer Edition
  • Microsoft Visual Basic 2005

Notice

SYMPTOMS

When a ComboBox control is bound to a table field and that table field value is null in Microsoft Visual Studio 2005, in Microsoft Visual Studio .NET 2003, or in Microsoft Visual Studio .NET 2002, the sequence of next and previous values may not correctly appear. For example, when the record that contains the null value is not the first record in the recordset and then the record that contains the null value is reached, the ComboBox control will display the first entry that was in the list.

WORKAROUND

To work around this issue, insert a non-null record that informs the user to perform an action in the lookup recordset. Set that record to be the default value for the ComboBox control.

MORE INFORMATION

Steps to reproduce the behavior

  1. Start Microsoft Visual Studio .NET 2002, Visual Studio .NET 2003, or Visual Studio 2005.
  2. On the File menu, click New, and then click Project.
  3. In the New Project window, click Visual Basic Projects, click Windows Application, name the application ComboBoxBinding, and then click OK.

    Note In Visual Studio 2005, click Visual Basic under Project Types.
  4. In Design view of the Form1 form, rename the form to ComboBoxBinding, and then double-click and replace the autogenerated code with the following code example:
    Imports System
Imports System.ComponentModel
Imports System.Drawing
Imports System.Windows.Forms
Imports System.Data
Imports System.Data.SqlClient

Namespace Microsoft.Samples.WinForms.VB.ComboBoxBinding

    Public Class ComboBoxBinding
        Inherits System.Windows.Forms.Form

        Shared Sub Main()
            Application.Run(New ComboBoxBinding())
        End Sub

        Public Sub New()
            MyBase.New()

            ComboBoxBinding = Me

            '  This code is required by the Windows Forms Designer.
            InitializeComponent()

            ' Fill the DataSet.
            Dim con As SqlConnection = New SqlConnection("server=(local);Trusted_Connection=yes;database=northwind")
            Dim cmd As SqlDataAdapter = New SqlDataAdapter("Select * from Customers ", con)
            cmd.Fill(customersDataSet1, "Customers")
            Dim cmd1 As SqlDataAdapter = New SqlDataAdapter("Select StateCode, StateName from States", con)
            cmd1.Fill(DsStates1, "MyStates")

            ' Set up the Combobox control bindings.
            'comboBoxUSState.DataSource = USStates          ' Populate the list
            comboBoxUSState.DataSource = DsStates1.Tables("MyStates")
            comboBoxUSState.DisplayMember = "StateName"   ' Define the field that will be displayed.
            comboBoxUSState.ValueMember = "StateCode"     ' Define the field that will be used as the value.

            ' Bind the selected value of the ComboBox control to the Region field of the current
            ' Customer.
            comboBoxUSState.DataBindings.Add("SelectedValue", customersDataSet1, "Customers.Region")

            ' Set up the rest of the form bindings.
            textBoxID.DataBindings.Add("Text", customersDataSet1, "Customers.CustomerID")
            textBoxCity.DataBindings.Add("Text", customersDataSet1, "Customers.City")
            textBoxTitle.DataBindings.Add("Text", customersDataSet1, "Customers.ContactTitle")
            textBoxAddress.DataBindings.Add("Text", customersDataSet1, "Customers.Address")
            textBoxCompany.DataBindings.Add("Text", customersDataSet1, "Customers.CompanyName")
            textBoxContact.DataBindings.Add("Text", customersDataSet1, "Customers.ContactName")
            textBoxZip.DataBindings.Add("Text", customersDataSet1, "Customers.PostalCode")

            ' Handle position changing events for the DATA VCR panel.
            AddHandler Me.BindingContext(customersDataSet1, "Customers").PositionChanged, AddressOf customers_PositionChanged

            ' Set up the initial text for the DATA VCR panel.
            textBoxPosition.Text = "Record " + (Me.BindingContext(customersDataSet1, "Customers").Position + 1).ToString() + " of " + customersDataSet1.Customers.Count.ToString()

            ' Set the minimum form size.
            Me.MinimumSize = New Size(375, 361)
        End Sub


        ' When the MoveFirst button is clicked, set the position for the Customers table
        ' to the first record.
        Protected Sub buttonMoveFirst_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonMoveFirst.Click
            ' Unselect the previously selected comboBoxUSState value.
            Me.BindingContext(customersDataSet1, "Customers").Position = 0
        End Sub


        ' When the MoveLast button is clicked, set the position for the Customers table
        ' to the last record.
        Protected Sub buttonMoveLast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonMoveLast.Click
            ' Unselect the previously selected comboBoxUSState value.
            Me.BindingContext(customersDataSet1, "Customers").Position = customersDataSet1.Customers.Count - 1
        End Sub

        ' When the MoveNext button is clicked, increment the position for the Customers table.
        Protected Sub buttonMoveNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonMoveNext.Click

            If Me.BindingContext(customersDataSet1, "Customers").Position < customersDataSet1.Customers.Count - 1 Then
                ' Unselect the previously selected comboBoxUSState value.
                Me.BindingContext(customersDataSet1, "Customers").Position += 1
            End If
        End Sub


        ' When the MovePrev button is clicked, decrement the position for the Customers table.
        Protected Sub buttonMovePrev_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonMovePrev.Click

            If Me.BindingContext(customersDataSet1, "Customers").Position > 0 Then
                ' Unselect the previously selected comboBoxUSState value.
                Me.BindingContext(customersDataSet1, "Customers").Position -= 1
            End If
        End Sub


        ' The psition has changed. Update the DATA VCR panel.
        Protected Sub customers_PositionChanged(ByVal sender As Object, ByVal e As System.EventArgs)
            textBoxPosition.Text = "Record " + (Me.BindingContext(customersDataSet1, "Customers").Position + 1).ToString() + " of " + customersDataSet1.Customers.Count.ToString()
        End Sub

        Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
            If disposing Then
                If Not (components Is Nothing) Then
                    components.Dispose()
                End If
            End If
            MyBase.Dispose(disposing)
        End Sub

#Region " Windows Form Designer generated code "

        Private components As System.ComponentModel.Container
        Private WithEvents customersDataSet1 As Microsoft.Samples.WinForms.VB.ComboBoxBinding.Data.CustomersDataSet
        Private WithEvents textBoxZip As System.Windows.Forms.TextBox
        Private WithEvents comboBoxUSState As System.Windows.Forms.ComboBox
        Private WithEvents textBoxCity As System.Windows.Forms.TextBox
        Private WithEvents labelUSState As System.Windows.Forms.Label
        Private WithEvents labelZip As System.Windows.Forms.Label
        Private WithEvents labelCity As System.Windows.Forms.Label
        Private WithEvents textBoxPosition As System.Windows.Forms.TextBox
        Private WithEvents buttonMoveFirst As System.Windows.Forms.Button
        Private WithEvents buttonMovePrev As System.Windows.Forms.Button
        Private WithEvents buttonMoveNext As System.Windows.Forms.Button
        Private WithEvents buttonMoveLast As System.Windows.Forms.Button
        Private WithEvents textBoxCompany As System.Windows.Forms.TextBox
        Private WithEvents labelCompanyName As System.Windows.Forms.Label
        Private WithEvents textBoxAddress As System.Windows.Forms.TextBox
        Private WithEvents textBoxTitle As System.Windows.Forms.TextBox
        Private WithEvents textBoxContact As System.Windows.Forms.TextBox
        Private WithEvents textBoxID As System.Windows.Forms.TextBox
        Private WithEvents labelAddress As System.Windows.Forms.Label
        Private WithEvents labelContactTitle As System.Windows.Forms.Label
        Private WithEvents labelContact As System.Windows.Forms.Label
        Private WithEvents labelID As System.Windows.Forms.Label
        Private WithEvents panelVCRControl As System.Windows.Forms.Panel

        Private WithEvents ComboBoxBinding As System.Windows.Forms.Form
        Friend WithEvents Button1 As System.Windows.Forms.Button
        Friend WithEvents SqlDataAdapter1 As System.Data.SqlClient.SqlDataAdapter
        Friend WithEvents SqlSelectCommand1 As System.Data.SqlClient.SqlCommand
        Friend WithEvents SqlConnection1 As System.Data.SqlClient.SqlConnection
        Friend WithEvents DsStates1 As dsStates

        Private Sub InitializeComponent()
            Me.labelCity = New System.Windows.Forms.Label()
            Me.buttonMoveNext = New System.Windows.Forms.Button()
            Me.customersDataSet1 = New Microsoft.Samples.WinForms.VB.ComboBoxBinding.Data.CustomersDataSet()
            Me.labelContact = New System.Windows.Forms.Label()
            Me.buttonMoveFirst = New System.Windows.Forms.Button()
            Me.textBoxID = New System.Windows.Forms.TextBox()
            Me.textBoxCity = New System.Windows.Forms.TextBox()
            Me.labelContactTitle = New System.Windows.Forms.Label()
            Me.labelCompanyName = New System.Windows.Forms.Label()
            Me.textBoxTitle = New System.Windows.Forms.TextBox()
            Me.textBoxPosition = New System.Windows.Forms.TextBox()
            Me.labelUSState = New System.Windows.Forms.Label()
            Me.buttonMovePrev = New System.Windows.Forms.Button()
            Me.labelZip = New System.Windows.Forms.Label()
            Me.textBoxAddress = New System.Windows.Forms.TextBox()
            Me.textBoxCompany = New System.Windows.Forms.TextBox()
            Me.panelVCRControl = New System.Windows.Forms.Panel()
            Me.buttonMoveLast = New System.Windows.Forms.Button()
            Me.comboBoxUSState = New System.Windows.Forms.ComboBox()
            Me.labelAddress = New System.Windows.Forms.Label()
            Me.labelID = New System.Windows.Forms.Label()
            Me.textBoxContact = New System.Windows.Forms.TextBox()
            Me.textBoxZip = New System.Windows.Forms.TextBox()
            Me.Button1 = New System.Windows.Forms.Button()
            Me.SqlDataAdapter1 = New System.Data.SqlClient.SqlDataAdapter()
            Me.SqlSelectCommand1 = New System.Data.SqlClient.SqlCommand()
            Me.SqlConnection1 = New System.Data.SqlClient.SqlConnection()
            Me.DsStates1 = New dsStates()
            CType(Me.customersDataSet1, System.ComponentModel.ISupportInitialize).BeginInit()
            Me.panelVCRControl.SuspendLayout()
            CType(Me.DsStates1, System.ComponentModel.ISupportInitialize).BeginInit()
            Me.SuspendLayout()
            '
            'labelCity
            '
            Me.labelCity.Location = New System.Drawing.Point(16, 176)
            Me.labelCity.Name = "labelCity"
            Me.labelCity.Size = New System.Drawing.Size(64, 16)
            Me.labelCity.TabIndex = 11
            Me.labelCity.Text = "City:"
            '
            'buttonMoveNext
            '
            Me.buttonMoveNext.Anchor = (System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Right)
            Me.buttonMoveNext.FlatStyle = System.Windows.Forms.FlatStyle.Flat
            Me.buttonMoveNext.Location = New System.Drawing.Point(280, 8)
            Me.buttonMoveNext.Name = "buttonMoveNext"
            Me.buttonMoveNext.Size = New System.Drawing.Size(32, 32)
            Me.buttonMoveNext.TabIndex = 2
            Me.buttonMoveNext.Text = ">"
            '
            'customersDataSet1
            '
            Me.customersDataSet1.DataSetName = "CustomersDataSet"
            Me.customersDataSet1.Locale = New System.Globalization.CultureInfo("en-US")
            '
            'labelContact
            '
            Me.labelContact.Location = New System.Drawing.Point(16, 80)
            Me.labelContact.Name = "labelContact"
            Me.labelContact.Size = New System.Drawing.Size(64, 16)
            Me.labelContact.TabIndex = 7
            Me.labelContact.Text = "Contact:"
            '
            'buttonMoveFirst
            '
            Me.buttonMoveFirst.FlatStyle = System.Windows.Forms.FlatStyle.Flat
            Me.buttonMoveFirst.Location = New System.Drawing.Point(8, 8)
            Me.buttonMoveFirst.Name = "buttonMoveFirst"
            Me.buttonMoveFirst.Size = New System.Drawing.Size(32, 32)
            Me.buttonMoveFirst.TabIndex = 0
            Me.buttonMoveFirst.Text = "|<"
            '
            'textBoxID
            '
            Me.textBoxID.Anchor = ((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxID.Enabled = False
            Me.textBoxID.Location = New System.Drawing.Point(88, 16)
            Me.textBoxID.Name = "textBoxID"
            Me.textBoxID.ReadOnly = True
            Me.textBoxID.Size = New System.Drawing.Size(299, 20)
            Me.textBoxID.TabIndex = 0
            Me.textBoxID.Text = ""
            '
            'textBoxCity
            '
            Me.textBoxCity.Anchor = ((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxCity.Location = New System.Drawing.Point(88, 176)
            Me.textBoxCity.Name = "textBoxCity"
            Me.textBoxCity.Size = New System.Drawing.Size(216, 20)
            Me.textBoxCity.TabIndex = 5
            Me.textBoxCity.Text = ""
            '
            'labelContactTitle
            '
            Me.labelContactTitle.Location = New System.Drawing.Point(16, 112)
            Me.labelContactTitle.Name = "labelContactTitle"
            Me.labelContactTitle.Size = New System.Drawing.Size(64, 16)
            Me.labelContactTitle.TabIndex = 8
            Me.labelContactTitle.Text = "Title:"
            '
            'labelCompanyName
            '
            Me.labelCompanyName.Location = New System.Drawing.Point(16, 48)
            Me.labelCompanyName.Name = "labelCompanyName"
            Me.labelCompanyName.Size = New System.Drawing.Size(64, 16)
            Me.labelCompanyName.TabIndex = 6
            Me.labelCompanyName.Text = "Company:"
            '
            'textBoxTitle
            '
            Me.textBoxTitle.Anchor = ((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxTitle.Location = New System.Drawing.Point(88, 112)
            Me.textBoxTitle.Name = "textBoxTitle"
            Me.textBoxTitle.Size = New System.Drawing.Size(216, 20)
            Me.textBoxTitle.TabIndex = 3
            Me.textBoxTitle.Text = ""
            '
            'textBoxPosition
            '
            Me.textBoxPosition.Anchor = (System.Windows.Forms.AnchorStyles.Left Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxPosition.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
            Me.textBoxPosition.Enabled = False
            Me.textBoxPosition.Location = New System.Drawing.Point(88, 14)
            Me.textBoxPosition.Name = "textBoxPosition"
            Me.textBoxPosition.ReadOnly = True
            Me.textBoxPosition.Size = New System.Drawing.Size(184, 20)
            Me.textBoxPosition.TabIndex = 1
            Me.textBoxPosition.Text = ""
            '
            'labelUSState
            '
            Me.labelUSState.Location = New System.Drawing.Point(16, 208)
            Me.labelUSState.Name = "labelUSState"
            Me.labelUSState.Size = New System.Drawing.Size(64, 16)
            Me.labelUSState.TabIndex = 13
            Me.labelUSState.Text = "US State:"
            '
            'buttonMovePrev
            '
            Me.buttonMovePrev.FlatStyle = System.Windows.Forms.FlatStyle.Flat
            Me.buttonMovePrev.Location = New System.Drawing.Point(48, 8)
            Me.buttonMovePrev.Name = "buttonMovePrev"
            Me.buttonMovePrev.Size = New System.Drawing.Size(32, 32)
            Me.buttonMovePrev.TabIndex = 1
            Me.buttonMovePrev.Text = "<"
            '
            'labelZip
            '
            Me.labelZip.Location = New System.Drawing.Point(16, 240)
            Me.labelZip.Name = "labelZip"
            Me.labelZip.Size = New System.Drawing.Size(64, 16)
            Me.labelZip.TabIndex = 12
            Me.labelZip.Text = "Zip:"
            '
            'textBoxAddress
            '
            Me.textBoxAddress.AcceptsReturn = True
            Me.textBoxAddress.Anchor = (((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Bottom) _
                        Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxAddress.Location = New System.Drawing.Point(88, 144)
            Me.textBoxAddress.Name = "textBoxAddress"
            Me.textBoxAddress.Size = New System.Drawing.Size(360, 20)
            Me.textBoxAddress.TabIndex = 4
            Me.textBoxAddress.Text = ""
            '
            'textBoxCompany
            '
            Me.textBoxCompany.Anchor = ((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxCompany.Location = New System.Drawing.Point(88, 48)
            Me.textBoxCompany.Name = "textBoxCompany"
            Me.textBoxCompany.Size = New System.Drawing.Size(296, 20)
            Me.textBoxCompany.TabIndex = 1
            Me.textBoxCompany.Text = ""
            '
            'panelVCRControl
            '
            Me.panelVCRControl.Anchor = ((System.Windows.Forms.AnchorStyles.Bottom Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.panelVCRControl.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle
            Me.panelVCRControl.Controls.AddRange(New System.Windows.Forms.Control() {Me.textBoxPosition, Me.buttonMoveFirst, Me.buttonMovePrev, Me.buttonMoveNext, Me.buttonMoveLast})
            Me.panelVCRControl.Location = New System.Drawing.Point(88, 288)
            Me.panelVCRControl.Name = "panelVCRControl"
            Me.panelVCRControl.Size = New System.Drawing.Size(360, 48)
            Me.panelVCRControl.TabIndex = 8
            Me.panelVCRControl.Text = "panel1"
            '
            'buttonMoveLast
            '
            Me.buttonMoveLast.Anchor = (System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Right)
            Me.buttonMoveLast.FlatStyle = System.Windows.Forms.FlatStyle.Flat
            Me.buttonMoveLast.Location = New System.Drawing.Point(320, 8)
            Me.buttonMoveLast.Name = "buttonMoveLast"
            Me.buttonMoveLast.Size = New System.Drawing.Size(32, 32)
            Me.buttonMoveLast.TabIndex = 3
            Me.buttonMoveLast.Text = ">|"
            '
            'comboBoxUSState
            '
            Me.comboBoxUSState.Location = New System.Drawing.Point(88, 208)
            Me.comboBoxUSState.Name = "comboBoxUSState"
            Me.comboBoxUSState.Size = New System.Drawing.Size(176, 21)
            Me.comboBoxUSState.TabIndex = 6
            '
            'labelAddress
            '
            Me.labelAddress.Location = New System.Drawing.Point(16, 144)
            Me.labelAddress.Name = "labelAddress"
            Me.labelAddress.Size = New System.Drawing.Size(64, 16)
            Me.labelAddress.TabIndex = 9
            Me.labelAddress.Text = "Address:"
            '
            'labelID
            '
            Me.labelID.Location = New System.Drawing.Point(16, 16)
            Me.labelID.Name = "labelID"
            Me.labelID.Size = New System.Drawing.Size(64, 16)
            Me.labelID.TabIndex = 5
            Me.labelID.Text = "ID:"
            '
            'textBoxContact
            '
            Me.textBoxContact.Anchor = ((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                        Or System.Windows.Forms.AnchorStyles.Right)
            Me.textBoxContact.Location = New System.Drawing.Point(88, 80)
            Me.textBoxContact.Name = "textBoxContact"
            Me.textBoxContact.Size = New System.Drawing.Size(339, 20)
            Me.textBoxContact.TabIndex = 2
            Me.textBoxContact.Text = ""
            '
            'textBoxZip
            '
            Me.textBoxZip.Location = New System.Drawing.Point(88, 240)
            Me.textBoxZip.Name = "textBoxZip"
            Me.textBoxZip.Size = New System.Drawing.Size(112, 20)
            Me.textBoxZip.TabIndex = 7
            Me.textBoxZip.Text = ""
            '
            'Button1
            '
            Me.Button1.Location = New System.Drawing.Point(276, 208)
            Me.Button1.Name = "Button1"
            Me.Button1.Size = New System.Drawing.Size(176, 23)
            Me.Button1.TabIndex = 14
            Me.Button1.Text = "Show Values"
            '
            'SqlDataAdapter1
            '
            Me.SqlDataAdapter1.SelectCommand = Me.SqlSelectCommand1
            Me.SqlDataAdapter1.TableMappings.AddRange(New System.Data.Common.DataTableMapping() {New System.Data.Common.DataTableMapping("Table", "States", New System.Data.Common.DataColumnMapping() {New System.Data.Common.DataColumnMapping("StateCode", "StateCode"), New System.Data.Common.DataColumnMapping("StateName", "StateName")})})
            '
            'SqlSelectCommand1
            '
            Me.SqlSelectCommand1.CommandText = "SELECT StateCode, StateName FROM States"
            Me.SqlSelectCommand1.Connection = Me.SqlConnection1
            '
            'SqlConnection1
            '
            Me.SqlConnection1.ConnectionString = "data source=OSPREY;initial catalog=Northwind;persist security info=False;user id=" & _
            "sa;workstation id=OSPREY;packet size=4096"
            '
            'DsStates1
            '
            Me.DsStates1.DataSetName = "dsStates"
            Me.DsStates1.Locale = New System.Globalization.CultureInfo("en-US")
            Me.DsStates1.Namespace = "http://www.tempuri.org/dsStates.xsd"
            '
            'ComboBoxBinding
            '
            Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
            Me.ClientSize = New System.Drawing.Size(464, 357)
            Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.Button1, Me.textBoxZip, Me.comboBoxUSState, Me.textBoxCity, Me.labelUSState, Me.labelZip, Me.labelCity, Me.panelVCRControl, Me.textBoxCompany, Me.labelCompanyName, Me.textBoxAddress, Me.textBoxTitle, Me.textBoxContact, Me.textBoxID, Me.labelAddress, Me.labelContactTitle, Me.labelContact, Me.labelID})
            Me.Name = "ComboBoxBinding"
            Me.Text = "Customer Details"
            CType(Me.customersDataSet1, System.ComponentModel.ISupportInitialize).EndInit()
            Me.panelVCRControl.ResumeLayout(False)
            CType(Me.DsStates1, System.ComponentModel.ISupportInitialize).EndInit()
            Me.ResumeLayout(False)

        End Sub

#End Region

        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
            'If Me.comboBoxUSState.Text <> "" Then
            MessageBox.Show("SelectedValue: " & Me.comboBoxUSState.SelectedValue.ToString & _
                " Text: " & Me.comboBoxUSState.Text.ToString & " SelectedIndex: " & Me.comboBoxUSState.SelectedIndex.ToString)
            'End If
        End Sub

        Private Sub comboBoxUSState_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles comboBoxUSState.SelectedIndexChanged

            'If Me.comboBoxUSState.Text <> "" Then
            '    MessageBox.Show(Me.comboBoxUSState.SelectedValue.ToString & " : " & Me.comboBoxUSState.Text.ToString)
            'End If
        End Sub
    End Class

End Namespace
    Note You must change the code in Visual Basic 2005. By default, Visual Basic creates two files for the project when you create a Windows Forms project. If the form is named Form1, the two files that represent the form are named Form1.vb and Form1.Designer.vb. You write the code in the Form1.vb file. The Windows Forms Designer writes the code in the Form1.Designer.vb file. The Windows Forms Designer uses the partial keyword to divide the implementation of Form1 into two separate files. This behavior prevents the designer-generated code from being interspersed with your code.

    For more information about the new Visual Basic 2005 language enhancements, visit the following Microsoft Developer Network (MSDN) Web site:

    http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnhcvs04/html/vs04k1.asp

    For more information about partial classes and the Windows Forms Designer, visit the following MSDN Web site:

    http://msdn2.microsoft.com/en-us/library/ms171843.aspx

  5. On the Project menu, click Add Class, click VB Class, and then click Open.
  6. In Design view, name the class as dsStates by replacing the autogenerated code with the following code example:
    Option Strict Off
Option Explicit On

Imports System
Imports System.Data
Imports System.Runtime.Serialization
Imports System.Xml


<Serializable(),  _
 System.ComponentModel.DesignerCategoryAttribute("code"),  _
 System.Diagnostics.DebuggerStepThrough(),  _
 System.ComponentModel.ToolboxItem(true)>  _
Public Class dsStates
    Inherits DataSet
    
    Private tableStates As StatesDataTable
    
    Public Sub New()
        MyBase.New
        Me.InitClass
        Dim schemaChangedHandler As System.ComponentModel.CollectionChangeEventHandler = AddressOf Me.SchemaChanged
        AddHandler Me.Tables.CollectionChanged, schemaChangedHandler
        AddHandler Me.Relations.CollectionChanged, schemaChangedHandler
    End Sub
    
    Protected Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)
        MyBase.New
        Dim strSchema As String = CType(info.GetValue("XmlSchema", GetType(System.String)),String)
        If (Not (strSchema) Is Nothing) Then
            Dim ds As DataSet = New DataSet
            ds.ReadXmlSchema(New XmlTextReader(New System.IO.StringReader(strSchema)))
            If (Not (ds.Tables("States")) Is Nothing) Then
                Me.Tables.Add(New StatesDataTable(ds.Tables("States")))
            End If
            Me.DataSetName = ds.DataSetName
            Me.Prefix = ds.Prefix
            Me.Namespace = ds.Namespace
            Me.Locale = ds.Locale
            Me.CaseSensitive = ds.CaseSensitive
            Me.EnforceConstraints = ds.EnforceConstraints
            Me.Merge(ds, false, System.Data.MissingSchemaAction.Add)
            Me.InitVars
        Else
            Me.InitClass
        End If
        Me.GetSerializationData(info, context)
        Dim schemaChangedHandler As System.ComponentModel.CollectionChangeEventHandler = AddressOf Me.SchemaChanged
        AddHandler Me.Tables.CollectionChanged, schemaChangedHandler
        AddHandler Me.Relations.CollectionChanged, schemaChangedHandler
    End Sub
    
    <System.ComponentModel.Browsable(false),  _
     System.ComponentModel.DesignerSerializationVisibilityAttribute(System.ComponentModel.DesignerSerializationVisibility.Content)>  _
    Public ReadOnly Property States As StatesDataTable
        Get
            Return Me.tableStates
        End Get
    End Property
    
    Public Overrides Function Clone() As DataSet
        Dim cln As dsStates = CType(MyBase.Clone,dsStates)
        cln.InitVars
        Return cln
    End Function
    
    Protected Overrides Function ShouldSerializeTables() As Boolean
        Return false
    End Function
    
    Protected Overrides Function ShouldSerializeRelations() As Boolean
        Return false
    End Function
    
    Protected Overrides Sub ReadXmlSerializable(ByVal reader As XmlReader)
        Me.Reset
        Dim ds As DataSet = New DataSet
        ds.ReadXml(reader)
        If (Not (ds.Tables("States")) Is Nothing) Then
            Me.Tables.Add(New StatesDataTable(ds.Tables("States")))
        End If
        Me.DataSetName = ds.DataSetName
        Me.Prefix = ds.Prefix
        Me.Namespace = ds.Namespace
        Me.Locale = ds.Locale
        Me.CaseSensitive = ds.CaseSensitive
        Me.EnforceConstraints = ds.EnforceConstraints
        Me.Merge(ds, false, System.Data.MissingSchemaAction.Add)
        Me.InitVars
    End Sub
    
    Protected Overrides Function GetSchemaSerializable() As System.Xml.Schema.XmlSchema
        Dim stream As System.IO.MemoryStream = New System.IO.MemoryStream
        Me.WriteXmlSchema(New XmlTextWriter(stream, Nothing))
        stream.Position = 0
        Return System.Xml.Schema.XmlSchema.Read(New XmlTextReader(stream), Nothing)
    End Function
    
    Friend Sub InitVars()
        Me.tableStates = CType(Me.Tables("States"),StatesDataTable)
        If (Not (Me.tableStates) Is Nothing) Then
            Me.tableStates.InitVars
        End If
    End Sub
    
    Private Sub InitClass()
        Me.DataSetName = "dsStates"
        Me.Prefix = ""
        Me.Namespace = "http://www.tempuri.org/dsStates.xsd"
        Me.Locale = New System.Globalization.CultureInfo("en-US")
        Me.CaseSensitive = false
        Me.EnforceConstraints = true
        Me.tableStates = New StatesDataTable
        Me.Tables.Add(Me.tableStates)
    End Sub
    
    Private Function ShouldSerializeStates() As Boolean
        Return false
    End Function
    
    Private Sub SchemaChanged(ByVal sender As Object, ByVal e As System.ComponentModel.CollectionChangeEventArgs)
        If (e.Action = System.ComponentModel.CollectionChangeAction.Remove) Then
            Me.InitVars
        End If
    End Sub
    
    Public Delegate Sub StatesRowChangeEventHandler(ByVal sender As Object, ByVal e As StatesRowChangeEvent)
    
    <System.Diagnostics.DebuggerStepThrough()>  _
    Public Class StatesDataTable
        Inherits DataTable
        Implements System.Collections.IEnumerable
        
        Private columnStateCode As DataColumn
        
        Private columnStateName As DataColumn
        
        Friend Sub New()
            MyBase.New("States")
            Me.InitClass
        End Sub
        
        Friend Sub New(ByVal table As DataTable)
            MyBase.New(table.TableName)
            If (table.CaseSensitive <> table.DataSet.CaseSensitive) Then
                Me.CaseSensitive = table.CaseSensitive
            End If
            If (table.Locale.ToString <> table.DataSet.Locale.ToString) Then
                Me.Locale = table.Locale
            End If
            If (table.Namespace <> table.DataSet.Namespace) Then
                Me.Namespace = table.Namespace
            End If
            Me.Prefix = table.Prefix
            Me.MinimumCapacity = table.MinimumCapacity
            Me.DisplayExpression = table.DisplayExpression
        End Sub
        
        <System.ComponentModel.Browsable(false)>  _
        Public ReadOnly Property Count As Integer
            Get
                Return Me.Rows.Count
            End Get
        End Property
        
        Friend ReadOnly Property StateCodeColumn As DataColumn
            Get
                Return Me.columnStateCode
            End Get
        End Property
        
        Friend ReadOnly Property StateNameColumn As DataColumn
            Get
                Return Me.columnStateName
            End Get
        End Property
        
        Public Default ReadOnly Property Item(ByVal index As Integer) As StatesRow
            Get
                Return CType(Me.Rows(index),StatesRow)
            End Get
        End Property
        
        Public Event StatesRowChanged As StatesRowChangeEventHandler
        
        Public Event StatesRowChanging As StatesRowChangeEventHandler
        
        Public Event StatesRowDeleted As StatesRowChangeEventHandler
        
        Public Event StatesRowDeleting As StatesRowChangeEventHandler
        
        Public Overloads Sub AddStatesRow(ByVal row As StatesRow)
            Me.Rows.Add(row)
        End Sub
        
        Public Overloads Function AddStatesRow(ByVal StateCode As String, ByVal StateName As String) As StatesRow
            Dim rowStatesRow As StatesRow = CType(Me.NewRow,StatesRow)
            rowStatesRow.ItemArray = New Object() {StateCode, StateName}
            Me.Rows.Add(rowStatesRow)
            Return rowStatesRow
        End Function
        
        Public Function FindByStateCode(ByVal StateCode As String) As StatesRow
            Return CType(Me.Rows.Find(New Object() {StateCode}),StatesRow)
        End Function
        
        Public Function GetEnumerator() As System.Collections.IEnumerator Implements System.Collections.IEnumerable.GetEnumerator
            Return Me.Rows.GetEnumerator
        End Function
        
        Public Overrides Function Clone() As DataTable
            Dim cln As StatesDataTable = CType(MyBase.Clone,StatesDataTable)
            cln.InitVars
            Return cln
        End Function
        
        Protected Overrides Function CreateInstance() As DataTable
            Return New StatesDataTable
        End Function
        
        Friend Sub InitVars()
            Me.columnStateCode = Me.Columns("StateCode")
            Me.columnStateName = Me.Columns("StateName")
        End Sub
        
        Private Sub InitClass()
            Me.columnStateCode = New DataColumn("StateCode", GetType(System.String), Nothing, System.Data.MappingType.Element)
            Me.Columns.Add(Me.columnStateCode)
            Me.columnStateName = New DataColumn("StateName", GetType(System.String), Nothing, System.Data.MappingType.Element)
            Me.Columns.Add(Me.columnStateName)
            Me.Constraints.Add(New UniqueConstraint("Constraint1", New DataColumn() {Me.columnStateCode}, true))
            Me.columnStateCode.AllowDBNull = false
            Me.columnStateCode.Unique = true
            Me.columnStateName.AllowDBNull = false
        End Sub
        
        Public Function NewStatesRow() As StatesRow
            Return CType(Me.NewRow,StatesRow)
        End Function
        
        Protected Overrides Function NewRowFromBuilder(ByVal builder As DataRowBuilder) As DataRow
            Return New StatesRow(builder)
        End Function
        
        Protected Overrides Function GetRowType() As System.Type
            Return GetType(StatesRow)
        End Function
        
        Protected Overrides Sub OnRowChanged(ByVal e As DataRowChangeEventArgs)
            MyBase.OnRowChanged(e)
            If (Not (Me.StatesRowChangedEvent) Is Nothing) Then
                RaiseEvent StatesRowChanged(Me, New StatesRowChangeEvent(CType(e.Row,StatesRow), e.Action))
            End If
        End Sub
        
        Protected Overrides Sub OnRowChanging(ByVal e As DataRowChangeEventArgs)
            MyBase.OnRowChanging(e)
            If (Not (Me.StatesRowChangingEvent) Is Nothing) Then
                RaiseEvent StatesRowChanging(Me, New StatesRowChangeEvent(CType(e.Row,StatesRow), e.Action))
            End If
        End Sub
        
        Protected Overrides Sub OnRowDeleted(ByVal e As DataRowChangeEventArgs)
            MyBase.OnRowDeleted(e)
            If (Not (Me.StatesRowDeletedEvent) Is Nothing) Then
                RaiseEvent StatesRowDeleted(Me, New StatesRowChangeEvent(CType(e.Row,StatesRow), e.Action))
            End If
        End Sub
        
        Protected Overrides Sub OnRowDeleting(ByVal e As DataRowChangeEventArgs)
            MyBase.OnRowDeleting(e)
            If (Not (Me.StatesRowDeletingEvent) Is Nothing) Then
                RaiseEvent StatesRowDeleting(Me, New StatesRowChangeEvent(CType(e.Row,StatesRow), e.Action))
            End If
        End Sub
        
        Public Sub RemoveStatesRow(ByVal row As StatesRow)
            Me.Rows.Remove(row)
        End Sub
    End Class
    
    <System.Diagnostics.DebuggerStepThrough()>  _
    Public Class StatesRow
        Inherits DataRow
        
        Private tableStates As StatesDataTable
        
        Friend Sub New(ByVal rb As DataRowBuilder)
            MyBase.New(rb)
            Me.tableStates = CType(Me.Table,StatesDataTable)
        End Sub
        
        Public Property StateCode As String
            Get
                Return CType(Me(Me.tableStates.StateCodeColumn),String)
            End Get
            Set
                Me(Me.tableStates.StateCodeColumn) = value
            End Set
        End Property
        
        Public Property StateName As String
            Get
                Return CType(Me(Me.tableStates.StateNameColumn),String)
            End Get
            Set
                Me(Me.tableStates.StateNameColumn) = value
            End Set
        End Property
    End Class
    
    <System.Diagnostics.DebuggerStepThrough()>  _
    Public Class StatesRowChangeEvent
        Inherits EventArgs
        
        Private eventRow As StatesRow
        
        Private eventAction As DataRowAction
        
        Public Sub New(ByVal row As StatesRow, ByVal action As DataRowAction)
            MyBase.New
            Me.eventRow = row
            Me.eventAction = action
        End Sub
        
        Public ReadOnly Property Row As StatesRow
            Get
                Return Me.eventRow
            End Get
        End Property
        
        Public ReadOnly Property Action As DataRowAction
            Get
                Return Me.eventAction
            End Get
        End Property
    End Class
End Class
  7. On the Project menu, click Add Class, click VB Class, and then click Open.
  8. In Design view, name the class as CustomerDataSet by replacing the autogenerated code with the following code example:
    Option Strict Off
Option Explicit On

Imports System
Imports System.Data
Imports System.Runtime.Serialization
Imports System.Xml


Namespace Microsoft.Samples.WinForms.VB.ComboBoxBinding.Data
    
    <Serializable(),  _
     System.ComponentModel.DesignerCategoryAttribute("code"),  _
     System.Diagnostics.DebuggerStepThrough(),  _
     System.ComponentModel.ToolboxItem(true)>  _
    Public Class CustomersDataSet
        Inherits DataSet
        
        Private tableCustomers As CustomersDataTable
        
        Public Sub New()
            MyBase.New
            Me.InitClass
            Dim schemaChangedHandler As System.ComponentModel.CollectionChangeEventHandler = AddressOf Me.SchemaChanged
            AddHandler Me.Tables.CollectionChanged, schemaChangedHandler
            AddHandler Me.Relations.CollectionChanged, schemaChangedHandler
        End Sub
        
        Protected Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)
            MyBase.New
            Dim strSchema As String = CType(info.GetValue("XmlSchema", GetType(System.String)),String)
            If (Not (strSchema) Is Nothing) Then
                Dim ds As DataSet = New DataSet
                ds.ReadXmlSchema(New XmlTextReader(New System.IO.StringReader(strSchema)))
                If (Not (ds.Tables("Customers")) Is Nothing) Then
                    Me.Tables.Add(New CustomersDataTable(ds.Tables("Customers")))
                End If
                Me.DataSetName = ds.DataSetName
                Me.Prefix = ds.Prefix
                Me.Namespace = ds.Namespace
                Me.Locale = ds.Locale
                Me.CaseSensitive = ds.CaseSensitive
                Me.EnforceConstraints = ds.EnforceConstraints
                Me.Merge(ds, false, System.Data.MissingSchemaAction.Add)
                Me.InitVars
            Else
                Me.InitClass
            End If
            Me.GetSerializationData(info, context)
            Dim schemaChangedHandler As System.ComponentModel.CollectionChangeEventHandler = AddressOf Me.SchemaChanged
            AddHandler Me.Tables.CollectionChanged, schemaChangedHandler
            AddHandler Me.Relations.CollectionChanged, schemaChangedHandler
        End Sub
        
        <System.ComponentModel.Browsable(false),  _
         System.ComponentModel.DesignerSerializationVisibilityAttribute(System.ComponentModel.DesignerSerializationVisibility.Content)>  _
        Public ReadOnly Property Customers As CustomersDataTable
            Get
                Return Me.tableCustomers
            End Get
        End Property
        
        Public Overrides Function Clone() As DataSet
            Dim cln As CustomersDataSet = CType(MyBase.Clone,CustomersDataSet)
            cln.InitVars
            Return cln
        End Function
        
        Protected Overrides Function ShouldSerializeTables() As Boolean
            Return false
        End Function
        
        Protected Overrides Function ShouldSerializeRelations() As Boolean
            Return false
        End Function
        
        Protected Overrides Sub ReadXmlSerializable(ByVal reader As XmlReader)
            Me.Reset
            Dim ds As DataSet = New DataSet
            ds.ReadXml(reader)
            If (Not (ds.Tables("Customers")) Is Nothing) Then
                Me.Tables.Add(New CustomersDataTable(ds.Tables("Customers")))
            End If
            Me.DataSetName = ds.DataSetName
            Me.Prefix = ds.Prefix
            Me.Namespace = ds.Namespace
            Me.Locale = ds.Locale
            Me.CaseSensitive = ds.CaseSensitive
            Me.EnforceConstraints = ds.EnforceConstraints
            Me.Merge(ds, false, System.Data.MissingSchemaAction.Add)
            Me.InitVars
        End Sub
        
        Protected Overrides Function GetSchemaSerializable() As System.Xml.Schema.XmlSchema
            Dim stream As System.IO.MemoryStream = New System.IO.MemoryStream
            Me.WriteXmlSchema(New XmlTextWriter(stream, Nothing))
            stream.Position = 0
            Return System.Xml.Schema.XmlSchema.Read(New XmlTextReader(stream), Nothing)
        End Function
        
        Friend Sub InitVars()
            Me.tableCustomers = CType(Me.Tables("Customers"),CustomersDataTable)
            If (Not (Me.tableCustomers) Is Nothing) Then
                Me.tableCustomers.InitVars
            End If
        End Sub
        
        Private Sub InitClass()
            Me.DataSetName = "CustomersDataSet"
            Me.Prefix = ""
            Me.Namespace = ""
            Me.Locale = New System.Globalization.CultureInfo("en-US")
            Me.CaseSensitive = false
            Me.EnforceConstraints = true
            Me.tableCustomers = New CustomersDataTable
            Me.Tables.Add(Me.tableCustomers)
        End Sub
        
        Private Function ShouldSerializeCustomers() As Boolean
            Return false
        End Function
        
        Private Sub SchemaChanged(ByVal sender As Object, ByVal e As System.ComponentModel.CollectionChangeEventArgs)
            If (e.Action = System.ComponentModel.CollectionChangeAction.Remove) Then
                Me.InitVars
            End If
        End Sub
        
        Public Delegate Sub CustomersRowChangeEventHandler(ByVal sender As Object, ByVal e As CustomersRowChangeEvent)
        
        <System.Diagnostics.DebuggerStepThrough()>  _
        Public Class CustomersDataTable
            Inherits DataTable
            Implements System.Collections.IEnumerable
            
            Private columnCustomerID As DataColumn
            
            Private columnCompanyName As DataColumn
            
            Private columnContactName As DataColumn
            
            Private columnContactTitle As DataColumn
            
            Private columnAddress As DataColumn
            
            Private columnCity As DataColumn
            
            Private column_Region As DataColumn
            
            Private columnPostalCode As DataColumn
            
            Private columnCountry As DataColumn
            
            Private columnPhone As DataColumn
            
            Private columnFax As DataColumn
            
            Friend Sub New()
                MyBase.New("Customers")
                Me.InitClass
            End Sub
            
            Friend Sub New(ByVal table As DataTable)
                MyBase.New(table.TableName)
                If (table.CaseSensitive <> table.DataSet.CaseSensitive) Then
                    Me.CaseSensitive = table.CaseSensitive
                End If
                If (table.Locale.ToString <> table.DataSet.Locale.ToString) Then
                    Me.Locale = table.Locale
                End If
                If (table.Namespace <> table.DataSet.Namespace) Then
                    Me.Namespace = table.Namespace
                End If
                Me.Prefix = table.Prefix
                Me.MinimumCapacity = table.MinimumCapacity
                Me.DisplayExpression = table.DisplayExpression
            End Sub
            
            <System.ComponentModel.Browsable(false)>  _
            Public ReadOnly Property Count As Integer
                Get
                    Return Me.Rows.Count
                End Get
            End Property
            
            Friend ReadOnly Property CustomerIDColumn As DataColumn
                Get
                    Return Me.columnCustomerID
                End Get
            End Property
            
            Friend ReadOnly Property CompanyNameColumn As DataColumn
                Get
                    Return Me.columnCompanyName
                End Get
            End Property
            
            Friend ReadOnly Property ContactNameColumn As DataColumn
                Get
                    Return Me.columnContactName
                End Get
            End Property
            
            Friend ReadOnly Property ContactTitleColumn As DataColumn
                Get
                    Return Me.columnContactTitle
                End Get
            End Property
            
            Friend ReadOnly Property AddressColumn As DataColumn
                Get
                    Return Me.columnAddress
                End Get
            End Property
            
            Friend ReadOnly Property CityColumn As DataColumn
                Get
                    Return Me.columnCity
                End Get
            End Property
            
            Friend ReadOnly Property _RegionColumn As DataColumn
                Get
                    Return Me.column_Region
                End Get
            End Property
            
            Friend ReadOnly Property PostalCodeColumn As DataColumn
                Get
                    Return Me.columnPostalCode
                End Get
            End Property
            
            Friend ReadOnly Property CountryColumn As DataColumn
                Get
                    Return Me.columnCountry
                End Get
            End Property
            
            Friend ReadOnly Property PhoneColumn As DataColumn
                Get
                    Return Me.columnPhone
                End Get
            End Property
            
            Friend ReadOnly Property FaxColumn As DataColumn
                Get
                    Return Me.columnFax
                End Get
            End Property
            
            Public Default ReadOnly Property Item(ByVal index As Integer) As CustomersRow
                Get
                    Return CType(Me.Rows(index),CustomersRow)
                End Get
            End Property
            
            Public Event CustomersRowChanged As CustomersRowChangeEventHandler
            
            Public Event CustomersRowChanging As CustomersRowChangeEventHandler
            
            Public Event CustomersRowDeleted As CustomersRowChangeEventHandler
            
            Public Event CustomersRowDeleting As CustomersRowChangeEventHandler
            
            Public Overloads Sub AddCustomersRow(ByVal row As CustomersRow)
                Me.Rows.Add(row)
            End Sub
            
            Public Overloads Function AddCustomersRow(ByVal CustomerID As String, ByVal CompanyName As String, ByVal ContactName As String, ByVal ContactTitle As String, ByVal Address As String, ByVal City As String, ByVal _Region As String, ByVal PostalCode As String, ByVal Country As String, ByVal Phone As String, ByVal Fax As String) As CustomersRow
                Dim rowCustomersRow As CustomersRow = CType(Me.NewRow,CustomersRow)
                rowCustomersRow.ItemArray = New Object() {CustomerID, CompanyName, ContactName, ContactTitle, Address, City, _Region, PostalCode, Country, Phone, Fax}
                Me.Rows.Add(rowCustomersRow)
                Return rowCustomersRow
            End Function
            
            Public Function GetEnumerator() As System.Collections.IEnumerator Implements System.Collections.IEnumerable.GetEnumerator
                Return Me.Rows.GetEnumerator
            End Function
            
            Public Overrides Function Clone() As DataTable
                Dim cln As CustomersDataTable = CType(MyBase.Clone,CustomersDataTable)
                cln.InitVars
                Return cln
            End Function
            
            Protected Overrides Function CreateInstance() As DataTable
                Return New CustomersDataTable
            End Function
            
            Friend Sub InitVars()
                Me.columnCustomerID = Me.Columns("CustomerID")
                Me.columnCompanyName = Me.Columns("CompanyName")
                Me.columnContactName = Me.Columns("ContactName")
                Me.columnContactTitle = Me.Columns("ContactTitle")
                Me.columnAddress = Me.Columns("Address")
                Me.columnCity = Me.Columns("City")
                Me.column_Region = Me.Columns("Region")
                Me.columnPostalCode = Me.Columns("PostalCode")
                Me.columnCountry = Me.Columns("Country")
                Me.columnPhone = Me.Columns("Phone")
                Me.columnFax = Me.Columns("Fax")
            End Sub
            
            Private Sub InitClass()
                Me.columnCustomerID = New DataColumn("CustomerID", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnCustomerID)
                Me.columnCompanyName = New DataColumn("CompanyName", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnCompanyName)
                Me.columnContactName = New DataColumn("ContactName", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnContactName)
                Me.columnContactTitle = New DataColumn("ContactTitle", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnContactTitle)
                Me.columnAddress = New DataColumn("Address", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnAddress)
                Me.columnCity = New DataColumn("City", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnCity)
                Me.column_Region = New DataColumn("Region", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.column_Region)
                Me.columnPostalCode = New DataColumn("PostalCode", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnPostalCode)
                Me.columnCountry = New DataColumn("Country", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnCountry)
                Me.columnPhone = New DataColumn("Phone", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnPhone)
                Me.columnFax = New DataColumn("Fax", GetType(System.String), Nothing, System.Data.MappingType.Element)
                Me.Columns.Add(Me.columnFax)
                Me.columnCustomerID.AllowDBNull = false
                Me.columnCompanyName.AllowDBNull = false
            End Sub
            
            Public Function NewCustomersRow() As CustomersRow
                Return CType(Me.NewRow,CustomersRow)
            End Function
            
            Protected Overrides Function NewRowFromBuilder(ByVal builder As DataRowBuilder) As DataRow
                Return New CustomersRow(builder)
            End Function
            
            Protected Overrides Function GetRowType() As System.Type
                Return GetType(CustomersRow)
            End Function
            
            Protected Overrides Sub OnRowChanged(ByVal e As DataRowChangeEventArgs)
                MyBase.OnRowChanged(e)
                If (Not (Me.CustomersRowChangedEvent) Is Nothing) Then
                    RaiseEvent CustomersRowChanged(Me, New CustomersRowChangeEvent(CType(e.Row,CustomersRow), e.Action))
                End If
            End Sub
            
            Protected Overrides Sub OnRowChanging(ByVal e As DataRowChangeEventArgs)
                MyBase.OnRowChanging(e)
                If (Not (Me.CustomersRowChangingEvent) Is Nothing) Then
                    RaiseEvent CustomersRowChanging(Me, New CustomersRowChangeEvent(CType(e.Row,CustomersRow), e.Action))
                End If
            End Sub
            
            Protected Overrides Sub OnRowDeleted(ByVal e As DataRowChangeEventArgs)
                MyBase.OnRowDeleted(e)
                If (Not (Me.CustomersRowDeletedEvent) Is Nothing) Then
                    RaiseEvent CustomersRowDeleted(Me, New CustomersRowChangeEvent(CType(e.Row,CustomersRow), e.Action))
                End If
            End Sub
            
            Protected Overrides Sub OnRowDeleting(ByVal e As DataRowChangeEventArgs)
                MyBase.OnRowDeleting(e)
                If (Not (Me.CustomersRowDeletingEvent) Is Nothing) Then
                    RaiseEvent CustomersRowDeleting(Me, New CustomersRowChangeEvent(CType(e.Row,CustomersRow), e.Action))
                End If
            End Sub
            
            Public Sub RemoveCustomersRow(ByVal row As CustomersRow)
                Me.Rows.Remove(row)
            End Sub
        End Class
        
        <System.Diagnostics.DebuggerStepThrough()>  _
        Public Class CustomersRow
            Inherits DataRow
            
            Private tableCustomers As CustomersDataTable
            
            Friend Sub New(ByVal rb As DataRowBuilder)
                MyBase.New(rb)
                Me.tableCustomers = CType(Me.Table,CustomersDataTable)
            End Sub
            
            Public Property CustomerID As String
                Get
                    Return CType(Me(Me.tableCustomers.CustomerIDColumn),String)
                End Get
                Set
                    Me(Me.tableCustomers.CustomerIDColumn) = value
                End Set
            End Property
            
            Public Property CompanyName As String
                Get
                    Return CType(Me(Me.tableCustomers.CompanyNameColumn),String)
                End Get
                Set
                    Me(Me.tableCustomers.CompanyNameColumn) = value
                End Set
            End Property
            
            Public Property ContactName As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.ContactNameColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.ContactNameColumn) = value
                End Set
            End Property
            
            Public Property ContactTitle As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.ContactTitleColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.ContactTitleColumn) = value
                End Set
            End Property
            
            Public Property Address As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.AddressColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.AddressColumn) = value
                End Set
            End Property
            
            Public Property City As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.CityColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.CityColumn) = value
                End Set
            End Property
            
            Public Property _Region As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers._RegionColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers._RegionColumn) = value
                End Set
            End Property
            
            Public Property PostalCode As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.PostalCodeColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.PostalCodeColumn) = value
                End Set
            End Property
            
            Public Property Country As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.CountryColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.CountryColumn) = value
                End Set
            End Property
            
            Public Property Phone As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.PhoneColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.PhoneColumn) = value
                End Set
            End Property
            
            Public Property Fax As String
                Get
                    Try 
                        Return CType(Me(Me.tableCustomers.FaxColumn),String)
                    Catch e As InvalidCastException
                        Throw New StrongTypingException("Cannot get value because it is DBNull.", e)
                    End Try
                End Get
                Set
                    Me(Me.tableCustomers.FaxColumn) = value
                End Set
            End Property
            
            Public Function IsContactNameNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.ContactNameColumn)
            End Function
            
            Public Sub SetContactNameNull()
                Me(Me.tableCustomers.ContactNameColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsContactTitleNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.ContactTitleColumn)
            End Function
            
            Public Sub SetContactTitleNull()
                Me(Me.tableCustomers.ContactTitleColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsAddressNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.AddressColumn)
            End Function
            
            Public Sub SetAddressNull()
                Me(Me.tableCustomers.AddressColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsCityNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.CityColumn)
            End Function
            
            Public Sub SetCityNull()
                Me(Me.tableCustomers.CityColumn) = System.Convert.DBNull
            End Sub
            
            Public Function Is_RegionNull() As Boolean
                Return Me.IsNull(Me.tableCustomers._RegionColumn)
            End Function
            
            Public Sub Set_RegionNull()
                Me(Me.tableCustomers._RegionColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsPostalCodeNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.PostalCodeColumn)
            End Function
            
            Public Sub SetPostalCodeNull()
                Me(Me.tableCustomers.PostalCodeColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsCountryNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.CountryColumn)
            End Function
            
            Public Sub SetCountryNull()
                Me(Me.tableCustomers.CountryColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsPhoneNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.PhoneColumn)
            End Function
            
            Public Sub SetPhoneNull()
                Me(Me.tableCustomers.PhoneColumn) = System.Convert.DBNull
            End Sub
            
            Public Function IsFaxNull() As Boolean
                Return Me.IsNull(Me.tableCustomers.FaxColumn)
            End Function
            
            Public Sub SetFaxNull()
                Me(Me.tableCustomers.FaxColumn) = System.Convert.DBNull
            End Sub
        End Class
        
        <System.Diagnostics.DebuggerStepThrough()>  _
        Public Class CustomersRowChangeEvent
            Inherits EventArgs
            
            Private eventRow As CustomersRow
            
            Private eventAction As DataRowAction
            
            Public Sub New(ByVal row As CustomersRow, ByVal action As DataRowAction)
                MyBase.New
                Me.eventRow = row
                Me.eventAction = action
            End Sub
            
            Public ReadOnly Property Row As CustomersRow
                Get
                    Return Me.eventRow
                End Get
            End Property
            
            Public ReadOnly Property Action As DataRowAction
                Get
                    Return Me.eventAction
                End Get
            End Property
        End Class
    End Class
End Namespace
  9. On the Project menu, click ComboBoxBinding properties, and then click Sub Main in the Start up Object list.

    Note In Visual Studio .NET 2002, right click ComboBoxBinding in Solution Explorer, click properties, choose Sub Main in Startup Object, and then click OK.

  10. On the Debug menu, click Start.
  11. Move through the Previous and Next records to see the behavior that is mentioned in the "Symptoms" section.
Modification Type:MinorLast Reviewed:10/3/2006
Keywords:kbvs2005swept kbvs2005applies kbprb KB894501 kbAudDeveloper
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