Memory Leak when using PrincipalSearcher.FindAll()

Question

I too have a long running service using plugins and appdomains and am having a memory leak due to using directoryservices. Note that I am using system.directoryservices.accountmanagement but it is my understanding that it uses the same underlying ADSI API's and hence is prone to the same memory leaks.

I've looked at all the CLR memory counters and the memory isn't being leaked there, and is all returned either on a forced GC or when I unload the appdomain. The leak is in private bytes which continually grow. I searched on here and have seen some issues related to a memory leak when using the ADSI API's but they seem to indicate that simply iterating over the directorysearcher fixes the problem. But as you can see in the code below, I am doing that in a foreach block and still the memory is being leaked. Any suggestions? Here is my method:

public override void JustGronkIT()
{
    using (log4net.ThreadContext.Stacks["NDC"].Push(GetMyMethodName()))
    {
        Log.Info("Inside " + GetMyMethodName() + " Method.");
        System.Configuration.AppSettingsReader reader = new System.Configuration.AppSettingsReader();
        //PrincipalContext AD = null;
        using (PrincipalContext AD = new PrincipalContext(ContextType.Domain, (string)reader.GetValue("Domain", typeof(string))))
        {
            UserPrincipal u = new UserPrincipal(AD);
            u.Enabled = true;
            //u.Surname = "ju*";
            using (PrincipalSearcher ps = new PrincipalSearcher(u))
            {
                myADUsers = new ADDataSet();
                myADUsers.ADUsers.MinimumCapacity = 60000;
                myADUsers.ADUsers.CaseSensitive = false;
                foreach (UserPrincipal result in ps.FindAll())
                {
                     myADUsers.ADUsers.AddADUsersRow(result.SamAccountName, result.GivenName, result.MiddleName, result.Surname, result.EmailAddress, result.VoiceTelephoneNumber,
                            result.UserPrincipalName, result.DistinguishedName, result.Description);
                 }
                 ps.Dispose();
            }
            Log.Info("Number of users: " + myADUsers.ADUsers.Count);
            AD.Dispose();
            u.Dispose();
        }//using AD
    }//Using log4net
}//JustGronkIT

I made the following changes to the foreach loop and it's better but private bytes still grows and is never reclaimed.

 foreach (UserPrincipal result in ps.FindAll())
 {
     using (result)
     {
         try
         {
             myADUsers.ADUsers.AddADUsersRow(result.SamAccountName, result.GivenName,           result.MiddleName, result.Surname, result.EmailAddress, result.VoiceTelephoneNumber,                                        result.UserPrincipalName, result.DistinguishedName, result.Description);
             result.Dispose();
         }
         catch
         {
             result.Dispose();
         }
     }
 }//foreach

Answer 1

I hit a big memory leak because, like you I wrote something like...

                foreach (GroupPrincipal result in searcher.FindAll())
                {
                    results.Add(result.Name);
                }

But the trick is that FindAll itself returns an object that must be disposed...

            using (var searchResults = searcher.FindAll())
            {
                foreach (GroupPrincipal result in searchResults)
                {
                    results.Add(result.Name);
                }
            }