Article ID: 197956 - Last Review: March 14, 2005 - Revision: 4.2

PRB: Passing Parameters By Reference to a VB COM Object

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This article was previously published under Q197956

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SYMPTOMS

When passing a parameter to a COM Component's method in Active Server Pages (ASP), the following error occurs:
Microsoft VBScript runtime error '800a000d' Type mismatch

Or the value stored in the variable passed to the method is not changed.
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CAUSE

VBScript will pass parameters to a method by value if the argument's data type is NOT declared as a variant and the parameter is passed by reference if the argument's data type is declared as variant by the method.
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RESOLUTION

Parameters to be passed by reference to a method should always be declared as a variant data type by the method, while parameters to be passed by value can be declared as any type by the method.
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STATUS

This behavior is by design.
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MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a Visual Basic ActiveX DLL Project called "ByRefProj."
  2. Add class module called "ByRefObj."
  3. Implement the following method:
    Public Sub ByRefMethod( ByRef strVal as String )
  strVal = "This variable is passed by Reference"
End Sub
  4. Create an ASP Page that calls this Method:
    <%
  Dim objTest, strByRefVal
  Set objTest = Server.CreateObject("ByRefProj.ByRefObj")
  objTest.ByRefMethod strByRefVal
%>
  5. Run ASP. The following error occurs:
    Microsoft VBScript runtime error '800a000d'
    Type mismatch: 'ByRefMethod'
To correct this behavior:

Change the implementation of the method ByRefMethod as follows: 
Public Sub ByRefMethod( ByRef strVal as Variant )
  strVal = "This variable is passed by Reference"
End Sub
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APPLIES TO
  • Microsoft Active Server Pages 4.0
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
  • Microsoft Internet Information Server 4.0
  • Microsoft Internet Information Services 5.0
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Keywords: 
kbcodesnippet kberrmsg kbprb KB197956
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