Share 'Get current GrasshopperDocument in C#'

Hello all I am working in a Grasshopper project using C# and Visual Studio 2012. I would like to know how can I get my current Grasshopper document to work with it. For example, I have declared my variable: private GH_Document GrasshopperDocument; But GH_Document doesn't have any methods to get my active document. Can someone help me? I'd like to do this private GH_Document GrasshopperDocumen…