C++ Screenshot using glReadPixels and integration on c#

Hello, I believe that's necessary to use that funciton (glReadPixels), but I am not a coder so, I wait for answers. What I need is a code that take screenshot inside a opengl game that returns black screenshots using the normal system. SO what I need is a solution for that. I heard that a software opensource called Taksi would do the job. Also after that I would need that full integrated in my C# program. Regards.