ASP.NET, C#, Active Directory - How do I display the fullname?

First off: I am using ASP.NET C# and Active Directory.

My question is... I have a login system that works off of active directory / windows auth.  When the person logs in I currently have their login name showing (i.e. Welcome smithjo) I would like to show their full name (i.e. Welcome Joe Smith!).  I have been looking all over and trying many examples of how to do this with no luck.

Can anyone help me out?  Currently I am using this code, which is throwing the error: System.NullReferenceException: Object reference not set to an instance of an object.

Code:

string ldapPath = "LDAP://test.com/OU=staff,DC=test,DC=com";
        DirectoryEntry currentUser = new DirectoryEntry(ldapPath);
 
        if (currentUser != null)
        {
            string firstName = currentUser.Properties["givenName"].Value.ToString();
            string lastName = currentUser.Properties["sn"].Value.ToString();
            lblFirstName.Text = firstName;
            lblLastName.Text = lastName;
        }
        else
        {
            lblUsername.Text = "Unknown User";
        }

Select allOpen in new window