The Type 'MySql.Data.MySqlClient.MySqlConnection' Exists In Both Error

I was using mysql .net connect 6.0.3. and visual web developer 2008. Then I have added the all the DLLs ("MySql.Data.CF.dll" "MySql.Data.dll" "MySql.Data.Entity.dll" "MySql.Web.dll" ) from the add references module. Then I have started getting this error The Type 'MySql.Data.MySqlClient.MySqlConnection' Exists In Both. Amazingly I just removed the references and it worked fine..