200分求得Designer的区别!

namespace test
{ [Designer("test.Designer,test"), DefaultProperty("Text"),
ToolboxData("<{0}:WebCustomControl1 runat=server></{0}:WebCustomControl1>")]
public class Charting : System.Web.UI.WebControls.WebControl
{请问以上代码中的Designer("test.Designer,test")与Designer("test.Designer")有何区别?
还有这个Designer后面的参数什么地方有更详细的介绍?