Is it possible to use a DLL created using C# in an unmanaged VC++ application?

Question

I have a DLL that I wrote in C# and I want to use it both with C# applications and applications written in unmanaged VC++. Is this possible?

Answer 1

There is more than just COM interop, the MSDN FAQ also lists lesser known methods:

2.2 How do I call .NET assembly from native Visual C++?

There are basically four methods to call .NET assembly from native VC++ code. Microsoft All-In-One Code Framework has working examples that demonstrate the methods.

1. Native VC++ module calls CLR Hosting APIs to host CLR, load and call the .NET assembly. (All-In-One Code Framework Sample Code: CppHostCLR)

2. If the .NET assembly can be exposed as a COM component, native VC++ module can call into the .NET assembly through .NET – COM interop. (All-In-One Code Framework Sample Code: CppCOMClient)

3. Reverse PInvoke: the managed code call native passing a delegate the native code can call back. (All-In-One Code Framework Sample Code: CSPInvokeDll)

4. If the module containing native VC++ code is allowed to enable CLR, the native VC++ code can call .NET assembly directly through the “It Just Works”, or “IJW”, mechanism. (All-In-One Code Framework Sample Code: CppCLIWrapLib)