How to get the groups of a user in Active Directory? (c#, asp.net)

If you’re on .NET 3.5 or up, you can use the new System.DirectoryServices.AccountManagement (S.DS.AM) namespace which makes this a lot easier than it used to be.

Read all about it here: Managing Directory Security Principals in the .NET Framework 3.5

Update: older MSDN magazine articles aren’t online anymore, unfortunately – you’ll need to download the CHM for the January 2008 MSDN magazine from Microsoft and read the article in there.

Basically, you need to have a “principal context” (typically your domain), a user principal, and then you get its groups very easily:

public List<GroupPrincipal> GetGroups(string userName)
{
   List<GroupPrincipal> result = new List<GroupPrincipal>();

   // establish domain context
   PrincipalContext yourDomain = new PrincipalContext(ContextType.Domain);

   // find your user
   UserPrincipal user = UserPrincipal.FindByIdentity(yourDomain, userName);

   // if found - grab its groups
   if(user != null)
   {
      PrincipalSearchResult<Principal> groups = user.GetAuthorizationGroups();

      // iterate over all groups
      foreach(Principal p in groups)
      {
         // make sure to add only group principals
         if(p is GroupPrincipal)
         {
             result.Add((GroupPrincipal)p);
         }
      }
   }

   return result;
}

and that’s all there is! You now have a result (a list) of authorization groups that user belongs to – iterate over them, print out their names or whatever you need to do.

Update: In order to access certain properties, which are not surfaced on the UserPrincipal object, you need to dig into the underlying DirectoryEntry:

public string GetDepartment(Principal principal)
{
    string result = string.Empty;

    DirectoryEntry de = (principal.GetUnderlyingObject() as DirectoryEntry);

    if (de != null)
    {
       if (de.Properties.Contains("department"))
       {
          result = de.Properties["department"][0].ToString();
       }
    }

    return result;
}

Update #2: seems shouldn’t be too hard to put these two snippets of code together…. but ok – here it goes:

public string GetDepartment(string username)
{
    string result = string.Empty;

    // if you do repeated domain access, you might want to do this *once* outside this method, 
    // and pass it in as a second parameter!
    PrincipalContext yourDomain = new PrincipalContext(ContextType.Domain);

    // find the user
    UserPrincipal user = UserPrincipal.FindByIdentity(yourDomain, username);

    // if user is found
    if(user != null)
    {
       // get DirectoryEntry underlying it
       DirectoryEntry de = (user.GetUnderlyingObject() as DirectoryEntry);

       if (de != null)
       {
          if (de.Properties.Contains("department"))
          {
             result = de.Properties["department"][0].ToString();
          }
       }
    }

    return result;
}