When you want to use COM objects and .NET Framework objects in the same application, you need to address the differences in how the objects exist in memory. A .NET Framework object is located in managed memory—the memory controlled by the common language runtime—and may be moved by the runtime as needed. A COM object is located in unmanaged memory and is not expected to move to another memory location. Visual Studio and the .NET Framework provide tools to control the interaction of these managed and unmanaged components. For more information about managed code, see Common Language Runtime.
In addition to using COM objects in .NET applications, you may also want to use Visual Basic to develop objects accessible from unmanaged code through COM.
The links on this page provide details on the interactions between COM and .NET Framework objects.