What are some issues I should consider when replacing the middle tier?
To transparently replace middle-tier components with .NET components without affecting client code, you must maintain the original GUIDS and ProgIDs of your COM components. In addition, you must properly handle replacement of the class interface generated by Visual Basic components when you attempt to transparently replace a COM component. You will have to translate the ADO.NET datasets that are returned from your upgraded middle-tier components to ADO recordsets that are used in your original Visual Basic code. You will need to deploy the interoperability assemblies for the middle tier components. Interoperability between Visual Basic .NET and Visual Basic 6.0 can become prevalent in this type of upgrade, depending on how you choose to define the application tiers. If the distance between the tiers is widened by making one side of the communication a .NET assembly, you may be increasing the amount of marshaling that is occurring in your application, which can negatively affect perform
