SUMMARY
This article demonstrates how to search for data in a
Windows Form
DataGrid control and synchronize the grid with the search results. In this
sample, you programmatically retrieve data into a
DataView class then bind the
DataView to the
DataGrid. The sample then allows users to type criteria in a text box and
click
Find to search for the record and move the pointer to the correct row
in the
DataGrid. This sample also indicates failure to locate a
record.
Description of the Technique
Setting Sort Order and Finding Records
To use the
DataView.Find method to find a record, you must set the sort order. In this
example, when you click the
DataGrid column header, the
DataGrid sets the sort order for you. The sample uses syntax to set the
sort order programmatically, which is very similar to the SQL ORDER BY syntax.
'Examples: Set the default sort order.
tblAuthors.DefaultView.Sort = "au_id"
tblAuthors.DefaultView.Sort = "au_id" vAuthors.Sort = "au_id DESC"
tblAuthors.DefaultView.Sort = "f_name,l_name" ' multi-column sort/find
Users can also change the sort order visually by clicking column
headers in the
DataGrid. Thus, when users click
Find, they use that column sort order to perform their
search.
Note The arrow in the column header indicates the current sort order,
and the direction of the arrow indicates whether the order is ascending or
descending.
Retrieving Current Sort Order Programmatically
To retrieve the current sort order and update the Label text,
read the
DataView.Sort property as follows:
dv.Sort
lblFind.Text = "Enter Search Criteria " & dv.Sort 'Used in this example to set out label.
Positioning the Record Pointer in a DataGrid
In this sample, you use the
DataView.Find method to retrieve the record position and update the
CurrencyManager object. This synchronizes the row pointer in the
DataGrid. If you want to highlight the row beyond this, you can use the
DataGrid.Select method.
This sample uses the
CurrencyManager object to manipulate currency. You can also use the
BindingManagerBase class, which is the base class for the
CurrencyManager. All data binding is done through
DataView classes. To synchronize your controls and the
CurrencyManager, the controls must be bound to the same
DataView.
'Search for the record in the DefaultView.
'If found, move the pointer to the correct record in the grid.
Dim i As Integer
i = dv.Find(txtFind.Text) ' Locates record in DefaultView.
' Does not move grid pointer or CM.
If i > dv.Table.Rows.Count Or i < 0 Then
MsgBox("Record Not found", MsgBoxStyle.Information, "Record Not Found")
Else
'CM.Position = i ' Synchronizes Cm and Grid Pointer.
End IfCreate the Sample
- Start Microsoft Visual Studio .NET.
- Create a new Windows Application in Visual Basic
.NET.
- Place a DataGrid control, a Button control, a Label control, and a TextBox control on the form.
- In the Properties window, set the properties for the
controls as follows:
Form Control
Name: frmFind
Size: 800, 520
Text: Search Form
Label Control
Name: lblFind
AutoSize: True
Location: 168, 456
Text: Enter Search Criteria au_id
TextBox Control
Name: txtFind
Location: 328, 456
Size: 216, 20
Text:
Button Control
Name: btnFind
Location: 560, 456
Size: 75, 32
Text: Find
DataGrid1 Control
Name: grdFind
Location: 16, 8
Size: 760,432
- Use the Imports statement on the System.Data.SqlClient namespace so that you are not required to qualify declarations
for this namespace later in your code. You must use this statement prior to Public Class frmFind and any other declarations. Add the following code to the frmFind
declarations section:
' Create namespace(s)
Imports System.Data.SqlClient
- Add the following variable declarations to frmFind after Public Class frmFind and before the rest of the code:
' Declare variables
Inherits System.Windows.Forms.Form
' Modify this string to correctly connect to your SQL Server.
Dim con As New SqlConnection("server=YourServerName;uid=YourUserId;" & _
"pwd=YourPassword;database=pubs")
Dim daAuthors As New SqlDataAdapter("Select * From Authors", con)
Dim ds As New DataSet()
Dim WithEvents dv As DataView
Dim CM As CurrencyManager - Add the following code to the frmFind_Load event:
' Retrieve data from the Authors table.
daAuthors.Fill(ds, "Authors")
dv = New DataView(ds.Tables("Authors"))
' Bind the data to the DataGrid.
grdFind.DataSource = dv
'Set the default sort order.
dv.Sort = "au_id"
' Initialize CurrencyManager to hold an instance of the form's CurrencyManager.
CM = frmFind.BindingContext(dv) - Add the following code to the btnFind_Click event:
' Verify that the user typed test to search for.
If txtFind.Text = "" Then
MsgBox("Please enter some criteria to find.")
txtFind.Focus()
Else
'Search for the record in the DefaultView.
'If found, move the pointer to the correct record in the grid.
Dim i As Integer
i = dv.Find(txtFind.Text) ' Locates record in DefaultView.
' Does not move grid pointer or CM.
If i > dv.Table.Rows.Count Or i < 0 Then
MsgBox("Record Not found", MsgBoxStyle.Information, "Record Not Found")
Else
CM.Position = i ' Synchronizes Cm and Grid Pointer.
End If
End If - Add the following code to the dv_ListChanged event:
' Strip the DESC off the dv.Sort string if the user has set the order to descending.
' This allows the Label2.Text to be properly displayed.
If dv.Sort.Substring((Len(dv.Sort) - 4), 4) = "DESC" Then
lblFind.Text = "Enter Search Criteria " & dv.Sort.Substring(0, Len(dv.Sort) - 5)
Else
lblFind.Text = "Enter Search Criteria " & dv.Sort
End If
- In Solution Explorer, select the project to set frmFind as
the startup form.
Note By default, the project is named WindowsApplication1. To rename
the form, click Properties on the Project menu. In the Startup Object drop-down list box, click frmFind, and then click OK to save your changes. - Save and run the application.
- Click the DataGrid header to change the sort order. Type criteria in the text box,
and then click Find. Notice that the record pointer is correctly positioned in the DataGrid.