title: GroupPrincipal.Members.Remove() doesn't work with a large AD group
body: <p>I'm using the <a href="http://msdn.microsoft.com/en-us/library/system.directoryservices.accountmanagement.aspx" rel="noreferrer">System.DirectoryServices.AccountManagement</a> namespace classes to manage the membership of several groups.  These groups control the population of our print accounting system and some of them are very large.  I'm running into a problem removing any user from one of these large groups.  I have a test program that illustrates the problem.  Note that the group I'm testing is not nested, but user.IsMemberOf() also seems to have the same problem, whereas GetAuthorizationGroups() correctly shows the groups a user is a member of.  The group in question has about 81K members, which is more than it should have since Remove() isn't working, and will normally be about 65K or so.</p>
  
  <p>I'd be interested to hear from other people who have had this problem and have resolved it.  I've got an open case with Microsoft, but the turn around on the call is slow since the call center is about 17 hours time difference so they don't arrive for work until about an hour before I usually leave for home.</p>
  
  <pre><code>using (var context = new PrincipalContext( ContextType.Domain ))
  {
      using (var group = GroupPrincipal.FindByIdentity( context, groupName ))
      {
          using (var user = UserPrincipal.FindByIdentity( context, userName ))
          {
              if (user != null)
              {
                  var isMember = user.GetAuthorizationGroups()
                                     .Any( g =&gt; g.DistinguishedName == group.DistinguishedName );
                  Console.WriteLine( "1: check for membership returns: {0}", isMember );
                  if (group.Members.Remove( user ))
                  {
                      Console.WriteLine( "user removed successfully" );
                      group.Save();
                  }
                  else
                  {
                      // do save in case Remove() is lying to me
                      group.Save();
                      Console.WriteLine( "user remove failed" );
                      var isStillMember = user.GetAuthorizationGroups()
                                              .Any( g =&gt; g.DistinguishedName == group.DistinguishedName );
                      Console.WriteLine( "2: check for membership returns: {0}", isStillMember );
  
                  }
              }
          }
      }
  }
  </code></pre>