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[HOWTO] Replace Collection with the VB6CollectionVariant type

Note: this article only applies to conversions to VB.NET, because the VB6Variant type isn’t supported when converting to C#.

The VB Migration Partner’s support library offers the special VB6CollectionVariant type, which behaves like a regular Collection except that its Item (default) member returns a VB6Variant value instead of Object instance.

You can perform the substitution in two different ways. The first method is the canonical approach, based on the ChangeType pragma:

        '## project:ChangeType Collection, VB6CollectionVariant

However, this approach might not suffice in certain cases, for example when an element of the collection is used with the Is or the TypeOf operator. In such cases, in fact, VB Migration Partner generates compilation errors:

        If myCollection("key") Is Nothing Then            ' <-- compilation error
            '…
        ElseIf TypeOf myCollection("key") Is Form Then    ' <-- compilation error
            '…
        End If

You can avoid these compilation errors by replacing the ChangeType pragma with the following PreProcess pragma (which must be stored in a *.pragmas file):

        '## project:PreProcess "(?<=\b(Is|As|New)\s+)(VBA\.)?Collection\b",
              "VBA.CollectionVariant"
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