C# - Get Local Groups And Not The Primary Groups For A Domain User

i have a code to get the groups a user belongs to.

try
{
DirectoryEntry adRoot = new DirectoryEntry(string.Format("WinNT://{0}", Environment.UserDomainName));
DirectoryEntry user = adRoot.Children.Find(completeUserName, "User");
object obGroups = user.Invoke("Groups");
foreach (object ob in (IEnumerable)obGroups)
{
// Create object for each group.
DirectoryEntry obGpEntry = new DirectoryEntry(ob);
listOfMyWindowsGroups.Add(obGpEntry.Name);
}
return true;
}
catch (Exception ex)
{
new GUIUtility().LogMessageToFile("Error in getting User MachineGroups = " + ex);
return false;
}

the above code works fine when i have to find the groups of a local user but

for a domain user it returns a value "Domain User" which is kind of wierd as it is a part of 2 local groups.

Research

I did some finding and got that i am being returned the primary group of the domain user

called "Domain User" group

but what i actually want is the groups of the local machines the domain user is a part of... i cannot get that.. any suggestions

another code using LDAP

string domain = Environment.UserDomainName;
DirectoryEntry DE = new DirectoryEntry("LDAP://" + domain, null, null, AuthenticationTypes.Secure);
DirectorySearcher search = new DirectorySearcher();
search.SearchRoot = DE;
search.Filter = "(SAMAccountName=" + completeUserName + ")"; //Searches active directory for the login name
search.PropertiesToLoad.Add("displayName"); // Once found, get a list of Groups
try
{
SearchResult result = search.FindOne(); // Grab the records and assign them to result
if (result != null)
{
DirectoryEntry theUser = result.GetDirectoryEntry();
theUser.RefreshCache(new string[] { "tokenGroups" });
foreach (byte[] resultBytes in theUser.Properties["tokenGroups"])
{
System.Security.Principal.SecurityIdentifier mySID = new System.Security.Principal.SecurityIdentifier(resultBytes, 0);
DirectorySearcher sidSearcher = new DirectorySearcher();
sidSearcher.SearchRoot = DE;
sidSearcher.Filter = "(objectSid=" + mySID.Value + ")";
sidSearcher.PropertiesToLoad.Add("distinguishedName");
SearchResult sidResult = sidSearcher.FindOne();
if (sidResult != null)
{
listOfMyWindowsGroups.Add((string)sidResult.Properties["distinguishedName"][0]);
}
}
}
else
{
new GUIUtility().LogMessageToFile("no user found");
}
return true;
}
catch (Exception ex)
{
new GUIUtility().LogMessageToFile("Error obtaining group names: " + ex.Message + " Please contact your administrator."); // If an error occurs report it to the user.
return false;
}

this works too but i get the same result "Domain Users" . Please can some1 tell me how to get the local machine groups...?