P/Invoke site

Platform invoke (a.k.a. P/Invoke or pinvoke) is the means of calling unmanaged code (typically in a DLL) from a .NET assembly. This allows you to leverage existing modules with new development. It's also useful for accessing the Win32 API when .NET doesn't quite provide the functionality you need (an all-too-common occurrence). A great site to help decipher the DllImport signature for Win32 function is http://www.pinvoke.net. It's a Wiki too, so you can add your experience to the site as you wish.