PRB: Using TypeOf as Part of an If Statement Fails

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SYMPTOMS

Using TypeOf as part of an If statement fails when it is used it on a control that was passed to a server application.

CAUSE

To resolve the type of an object through the TypeOf interface, remoting is required for the actual control type. However, there is no remoting capability for controls.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

Develop and run a container and a server application:

Create the Container Application

1. Start a new project in Visual Basic. Form1 is created by default.

2. From the Insert menu, choose Class Module to add Class1 to the project.

3. Set the properties of Class1 as follows:

      Property      Value
      ------------------------------------
      Instancing    1-Creatable SingleUse
      Name          Class1
      Public        True
   
   

4. Add the following code to the general declarations section of Class1:

   Public Sub DataLoadList(c)

         If TypeOf c Is ComboBox Then
            MsgBox "ComboBox"
         Else
            MsgBox "Not a ComboBox"
         End If
      End Sub
   
   

5. From the File menu, choose Make EXE File, and name the executable as Project1.

Create the Server Application

1. Start a new project in Visual Basic. Form1 is created by default.

2. Add the following code to the general declarations section of Form1:

      Private Sub localcheck(c)
         If TypeOf c Is ComboBox Then
            MsgBox "ComboBox"
         Else
            MsgBox "Not a ComboBox"
         End If
      End Sub
   
   

3. Add two command buttons (Command1 and Command2) and a ComboBox to Form1.

4. Add the following code to the Command1_Click event procedure:

      Private Sub Command2_Click()
         Call localcheck(Combo1)
      End Sub
   
   

5. Add the following code to the Command2_Click event procedure:

      Private Sub Command1_Click()
         Dim x As Object
         Set x = CreateObject("Project1.Class1")
         Call x.DataLoadList(Combo1)
         Set x = Nothing
      End Sub
   
   

6. Run PROJECT1.EXE from Program Manager or File Manager.

7. Run Project2 from the Visual Basic design environment. Click the Command1 button for a local check of the TypeOf statement. The message "ComboBox" is displayed in a message box. Click the Command2 button to test the TypeOf statement across processes and the message "Not a ComboBox" is displayed in a message box.