LibCurlDotNet is a project mainly written in C#, it's free.
C# bindings for libcurl
This is a pure C# wrapper for libcurl.
The entire libcurl API has not been exposed. Just enough to provide a proof of concept has been completed. See the Samples for completed functionality.
LibCurlDotNet does not require a C library to function. It is pure C#. It is based on http://sourceforge.net/projects/libcurl-net/. Of course see http://curl.haxx.se/ for more details on libcurl.