How to expose an ActiveX DLL as a Web service by using COM+ (317880)

SUMMARY

This step-by-step article describes how to use the COM+ Application Install Wizard that ships with the Component Services console in Microsoft Windows XP Professional to expose and consume a legacy Microsoft Visual Basic COM component as a Web service.

back to the top

Requirements

The following list outlines the recommended hardware, software, network infrastructure, and service packs that are required:

• Windows XP Professional or Windows Server 2003 with the Microsoft .NET Framework installed
• Microsoft Visual Basic 5.0 or later
• Microsoft Visual Studio .NET
• Microsoft SQL Server 7.0 or later, with the Northwind database

back to the top

Create a COM+ application

To create a COM+ application, follow these steps:

1. Create a small Visual Basic 5.0 or 6.0 application that contains a single method called OrderTotal. When you pass in an OrderID, this method issues a SELECT statement to the database and calculates the total price for that order. It then returns the order total.
2. On the Start menu, point to Programs, point to Microsoft Visual Studio 5.0 or Microsoft Visual Studio 6.0, and then click Microsoft Visual Basic 5.0 or Microsoft Visual Basic 6.0.
3. In New Project dialog box, select ActiveX DLL, and then click Open.
4. Press CTRL+R to open Project Explorer, select Project1, and then press F4 to access the properties for the project. Change the Name property to HowToCOMXP.
5. Select Class1.cls, and then change the Name property to Products.
6. In the Code Editor window, paste the following code in the Class module. Note that you may need to modify the connection string for your computer:

   Public Function OrderTotal(OrderID As String) As Double
           Dim cn As ADODB.Connection
           Set cn = New ADODB.Connection
           cn.ConnectionString = "provider=sqloledb;data source=(local);initial catalog=northwind;uid=sa"
           cn.Open
   
           Dim rs As ADOR.Recordset
           Set rs = New ADOR.Recordset
           rs.CursorLocation = adUseClient
           rs.CursorType = adOpenStatic
           rs.LockType = adLockBatchOptimistic
   
   rs.Open "select sum(unitprice * quantity) from [order details] where orderid=" & OrderID, cn
           rs.ActiveConnection = Nothing
           cn.Close
   
           OrderTotal = rs(0)
   End Function
   					

   This code creates a database connection and a recordset, and then returns the order total for any order in the Northwind database.
   
   
7. On the Project menu, click References. In the References dialog box, select Microsoft ActiveX Data Objects 2.7 Library and Microsoft ActiveX Data Objects Recordset 2.7 Library under Available References, and then click OK.
8. On the File menu, click Make HowToCOMXP.dll. To keep the path simple, select drive C in the Save in list. Accept the default file name, and then click OK.
9. On the Start menu, click Control Panel, click Administrative Tools, and then click Component Services.
10. In the Component Services dialog box, expand Component Services, expand Computers, and then expand My Computer. Right-click COM+ Applications, click New, and then click Application.
11. When the COM+ Application Install Wizard starts, click Next.
12. Click Create an empty application.
13. Type HowToCOMXP as the name of the application, and then click Next.
14. In the Set Application Identity page, verify that Interactive user is selected, click Next, and then click Finish. This creates the COM+ application.

back to the top

Add the ActiveX component to the COM+ application

After you have created the COM+ application, you must add the ActiveX component to that application. To do this, follow these steps:

1. In the left pane of the Component Services dialog box, expand COM+ Applications, and then expand HowToCOMXP. Right-click Components, click New, and then click Component.
2. When the COM+ Component Install Wizard starts, click Next.
3. Click Install new components. Browse to drive C, select HowToCOMXP.dll, and then click Open. Click Next, and then click Finish. This installs the dynamic-link library (DLL) in the COM+ application.

back to the top

Expose the DLL as a Web service

After you install the DLL in the COM+ application, you must expose the component as a Web service. To do this, follow these steps:

1. Right-click HowToCOMXP, and then click Properties.
2. On the Activation tab, click Uses SOAP. In the SOAP VRoot field, type HowToCOMXPWebService, and then click OK.
3. Browse to C:\Windows\system32\Com\SOAPVRoots\HowToCOMXPWebService to see the virtual root that is created automatically for that COM+ application.
4. Note the Default.aspx page in this folder. This is a valid URL. To browse to this page, start Microsoft Internet Explorer, and then type localhost/HowToCOMXPWebService in the Address field.
5. When the Web page for the Web service appears, click the link to view the Web Service Description Language (WSDL) document for the component that you installed in the HowToCOMXP COM+ application.
6. Close Component Services.

back to the top

Create a Windows application to consume the Web service

To create a Windows application that will serve as a client for (that is, "consume") the Web service, follow these steps:

1. On the Start menu, click Programs, click Microsoft Visual Studio .NET, and then click Microsoft Visual Studio .NET.
2. Click New Project. Under Project Types, click Visual Basic Projects, and then select Windows Application under Templates.
3. In the Name field, type COMXPClient.
4. When the project opens, press CTRL+ALT+X to open the Toolbox. Drag a TextBox control and a Button control onto Form1. Position the Button control to the right of the TextBox control.
5. Click the lower right corner of Form1, and then drag the cursor up and to the left to shrink Form1 so that an equal amount of space surrounds the controls.
6. Click the Button control, and then press F4 to access the properties for the control. Change the Text property to Order Total.
7. Click the TextBox control. In the Properties dialog box, delete the value for the Text property.

back to the top

Add a Web reference

To use the legacy COM object, you must add a Web reference. To do this, follow these steps:

1. In Solution Explorer, right-click References, and then click Add Web Reference.
2. In the Address field, type http://localhost/HowToCOMXPWebService/Legacy.Products.soap?wsdl.
3. Press ENTER. When the Add Reference button is enabled, click it to add the reference. You can now call into the COM object with standard Web service protocols.
4. On Form1, double-click the Button control to create a Click event handler, and then paste the following code in the event handler:

   Dim ws As New localhost.ProductsClassBinding()
   Dim Total As Double = ws.OrderTotal(TextBox1.Text)
   MessageBox.Show("Total Order : $" & Total)
   					

   The OrderTotal method that you created in the legacy Visual Basic DLL appears as a method of the Web service Proxy class.

back to the top

Test the procedure

1. Press F5 to run the application in Debug mode.
2. When the form appears, type 10248 in the field, and then click Order Total.
3. When you see "Total Order : $440" in the message box, click OK.
4. To view a different result, type 10249, and then click Order Total.

back to the top

Troubleshooting

If you open http://localhost/HowToCOMXPWebService in Internet Explorer and you can see the page but not the Web methods, the interface and method information for the component are not registered. This can occur when you use the Legacy Component Import Wizard to install the legacy components. To resolve this problem, delete and reinstall the COM+ application in Component Services.

back to the top

Complete code listings

Complete code listing (Products.cls)

Public Function OrderTotal(OrderID As String) As Double
        Dim cn As ADODB.Connection
        Set cn = New ADODB.Connection
        cn.ConnectionString = "provider=sqloledb;data source=(local);initial catalog=northwind;uid=sa"
        cn.Open

        Dim rs As ADOR.Recordset
        Set rs = New ADOR.Recordset
        rs.CursorLocation = adUseClient
        rs.CursorType = adOpenStatic
        rs.LockType = adLockBatchOptimistic

        rs.Open "select sum(unitprice * quantity) from [order details] where orderid=" & OrderID, cn
        rs.ActiveConnection = Nothing
        cn.Close

        OrderTotal = rs(0)
End Function
				

back to the top

Complete code listing (Form1.vb)

Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call.

    End Sub

    'The form overrides Dispose to clean up the component list.
    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

    'This is required by the Windows Form Designer.
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer.
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox()
        Me.Button1 = New System.Windows.Forms.Button()
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(24, 16)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.TabIndex = 0
        Me.TextBox1.Text = ""
        '
        'Button1
        '
        Me.Button1.Location = New System.Drawing.Point(136, 16)
        Me.Button1.Name = "Button1"
        Me.Button1.TabIndex = 1
        Me.Button1.Text = "Order Total"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(248, 62)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.Button1, Me.TextBox1})
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim ws As New localhost.ProductsClassBinding()
        Dim Total As Double = ws.OrderTotal(TextBox1.Text)
        MessageBox.Show("Total Order : $" & Total)
    End Sub
End Class
				

back to the top

REFERENCES

For more information about how to expose existing COM+ applications over SOAP by using Windows XP and the .NET Framework, see the following Microsoft Developer Network (MSDN) Web site: back to the top