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excel – VB.NET equivalent of VB6 Attribute Item.VB_UserMemId = 0

Posted by: admin March 9, 2020 Leave a comment

Questions:

I’ve upgraded a class from VB6 to VB.NET to be used in Excel via COM.

In VB6, I have a property defined in class MyScalars as this:

Public Property Get Item(vntIndexKey As Variant) As MyScalar
Attribute Item.VB_UserMemId = 0
    Set Item = mCol(vntIndexKey)
    ...
End Property

This seems to make it so that in Excel VBA, I can access this property without specifying it (so like a default property):

Dim oOut As Object
Set oOut = MyScalars(Range("E10").Value)

Is there an equivalent attribute in VB.NET that does this? I’ve tried the following but it gives an error in the VBA:

Default Public ReadOnly Property Item(ByVal vntIndexKey As String) As MyScalar
    Get
        If mCol.ContainsKey(vntIndexKey) Then
            Item = mCol.Item(vntIndexKey)
        End If
        ...
End Property
How to&Answers:

The reply of Govert is the right one.
All the members of a COM IDispatch interface are automatically marked with a DISPID value,
when converted from .NET to COM. The only exception for this automatic process is the value 0, which is reserved for the default member of the class. if you do not set the dispid, the default member of .NET classes when is ported to COM is the ::ToString method.
In your example:

< DispId(0) > _
Public ReadOnly Property Item(ByVal vntIndexKey As String) As MyScalar

End Property