If you want to host OpenCV code in a .NET application, you don't really need Python; it will be too long way around. OpenCV is written in C++, so you should better use this implementation in .NET. The work of embedding OpenCV code in a .NET assemblies is already done for you. People usually use open-source and multi-platform Emgu CV:
Emgu CV download | SourceForge.net[
^],
Emgu CV: OpenCV in .NET (C#, VB, C++ and more)[
^].
However, it's not clear what you really want to do. Perhaps you wanted to develop Python application using .NET UI. But that would also be too long way around. Perhaps you want this because you have more experience with Python; I just don't know. Anyway, if you feel that this solution won't work for you, please clarify. From what I see, you really need to use C# and OpenCV. In this tandem, the role of Python looks redundant to me.
—SA