Application Development Using Visual Basic® and .NET

Calling COM Components from Managed Code

The first interoperability scenario we will look at is managed code calling COM components. The .NET Framework makes it easy to create a Runtime Callable Wrapper (RCW), which acts as a bridge between managed and unmanaged code. The RCW is illustrated in Figure 17-1.

Figure 17-1. A Runtime Callable Wrapper between managed and unmanaged code.

You could implement an RCW assembly yourself, using the PInvoke facility (described in a later section) to call into the necessary APIs, such as CoCreateInstance and the IUnknown methods directly. But that is not necessary, because the Tlbimp.exe tool can read type library ...