How to get Scc provider GUID !

visual studio Tools->Options->Source control can set current source control plug-in , i can get current source control scc provider Guid from regedit table:HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\10.0\CurrentSourceControlProvider, but we need to close visual studio, then the KEY CurrentSourceControlProviderwill have current sccProvider GUID,

So how to get current scc provider GUID immediately or any other API can get scc provider GUID?

Thanks in advance! 

Regards,

Michael