SharpMap relies, for reprojection, on ProjNet. you must add a reference to that as well. Also iirc, a reference to brutile.dll needs to be added as well.
It is advised strongly to compile the sharpmap solution yourself, since the released versions are usually outdated ;-).
Here are the SVN links. Check them out, reference them by project in Visual Studio and you should be good to go. If you are running on Mono then definitely compile all of the code yourself...
SharpMap = https://sharpmap.svn.codeplex.com/svn
Brutile = https://brutile.svn.codeplex.com/svn
ProjNet = https://sharpmapcs.svn.codeplex.com/svn