When a Type structure (a.k.a. User-Defined Type, or UDT) appears in a Get or Put statement, VB Migration Partner ensures that the corresponding VB.NET structure implements the IVB6FileGetPut interface, which consists of the Read and Write methods). These two methods are indirectly invoked from inside the FileGet6 and FilePut6 methods and correctly read or write the structure’s individual methods.

VB Migration Partner can detect whether a structure needs to implement the IVB6FileGetPut interface only if the UDT is part of a project (or project group) that contains a Get or Put statement that acts on the UDT. However, if you are migrating an ActiveX DLL that defines a UDT that is read from or written to file in a project that isn’t part of the solution being migrated, the VB.NET structure won’t implement the IVB6FileGetPut interface and an error will eventually occur at runtime.

In cases like these you need to force VB Migration Partner to believe that the UDT is actually read/written to file. The easiest way to do so is by adding a method that reads/writes the UDT anywhere in the VB6 project, for example:

        '## OutputMode Off
        Sub DummyMethod()
            Dim udt As MyUDT
            Get #1, , udt
        End Sub
        '## OutputMode On

where the OutputMode pragmas ensure that the dummy method is removed from the generated VB.NET project.