How to modify share permission using C#?

Question

I am a newbie trying to write a C# app to change share permission. Can someone shine some light which class in the .Net FW I should use? I have tried to use System.ManagementServices (using WMI), but the object structure is just too different as WMI use GetSecurityDescriptor method which I can’t find within the .Net FW. Should I use ADSI class (System.DirectoryServices)? Any input is appreciated. Thanks.