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PRB: Can't Use Late Binding When Server Method Uses UDT

This article was previously published under Q184898
SYMPTOMS
When you have an ActiveX server that you created with Visual Basic version6.0, you receive an error when accessing a method or property that acceptsand/or returns a user-defined type (UDT).

You receive one of the following errors when accessing a method thatreturns a UDT or accepts a UDT as an argument:
Run-time Error '429':
ActiveX component can't create object
-or-
Compile error:
Only user-defined types defined in public object modules can be coerced
to or from a variant or passed to late-bound functions.
CAUSE
A method that returns or accepts a user-defined type (UDT) cannot be calledwhen using late binding.
   Dim oMyObject as Object   Dim MyUDT as Object   Set oMyObject = CreateObject("MyProject.MyClass")   MyUDT = oMyObject.MyMethod    '<-- This line generates a run-time error                                 '    if MyMethod returns a UDT.				
RESOLUTION
To correct this problem, you can use either of the following two solutions:
  • Use early binding instead of late binding.
  • Modify the server so that the method returns an object of another class rather than a UDT.
STATUS
This behavior is by design.
MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new ActiveX EXE project.
  2. On the Project menu, click Properties. Change the Project Name to "TestServer" and click OK.
  3. Add the following code to Class1:
          Public Type MyUDT         x as Long         y as Long      End Type      Public Function MyMethod() as MyUDT         MyMethod.x = 1         MyMethod.y = 2      End Function						
  4. On the File menu, click Make TestServer.EXE.
  5. Close this project and start a new Standard EXE project.
  6. Add two command buttons to Form1.
  7. Add the following code to Form1:
          Private Type MyUDT         x as Long         y as Long      End Type      Private Sub Command1_Click()         Dim obj1 as Object         Dim obj2 as Object         Set obj1 = CreateObject("TestServer.Class1")         obj2 = obj1.MyMethod           '<== Generates run-time error #429.      End Sub      Private Sub Command2_Click()         Dim obj1 as Object         Dim mu as MyUDT         Set obj1 = CreateObject("TestServer.Class1")         mu = obj1.MyMethod             '<== Generates compile error.      End Sub						
  8. Run the project by pressing F5 and click Command1. You receive the run-time error #429. Click End to end the program.
  9. Run the project once more and click Command2. You receive the compile error described at the beginning of this article.
REFERENCES
For information about binding ActiveX components in your project, refer tothe "Declaring an Object Variable" and "How Binding Affects ActiveXComponent Performance" topics in the Visual Basic product documentation.

For information about creating your own collection classes, refer to the"Using Properties and Collections to Create Object Models" topic in theVisual Basic product documentation.
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Article ID: 184898 - Last Review: 05/13/2003 21:48:00 - Revision: 3.0

  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • kbnofix kbprb KB184898
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