.net - Remove a user from all Active Directory Groups with C# -

i have wcf service written in c# performs actions on user , group objects in active directory. 1 of operations available on service need remove groups specific user.

i able using code, takes longer 30 seconds , i'd avoid expanding timeout.

foreach (groupprincipal group in user.getgroups(this._context)) {    // we've set primary group domain users want skip group now.    if (group.name.toupper().equals(domain_users.toupper()))    {       continue;    }     // remove user , save group.    group.members.remove(user);    group.save();    group.dispose(); } 

i tried code i'm getting error ad says "server unwilling perform request."

var userentry = (directoryentry)user.getunderlyingobject(); userentry.properties["memberof"].clear(); userentry.commitchanges(); userentry.dispose(); 

what can make first code block more efficient? there way remove user groups have not considered?