I'm working on MSSQL 2008, normally I prefer for drawing circle in sharmap in a such way:
Include Sqlserver types.dll to your project, then later on;
double xxxxx = new double();
Geometry Geom = new Geometry();
ToSharpMapGeometry(ToSqlGeometry(Geom).STBuffer(xxxxx) ) ;
then place it on a map...
there may be another easier solution ....But it is my solution...