access active directory frm another network using c#

Question

Active directory configure on the  different network and I want to access this active directory from another network ,how we can do this using c#.

Active directory is configured on the Network1 and we want to access this active directory from the ntework2

I have done the below code ant it is working fine with in the same network.

   public bool IsUserAuthenticated(string domain, string userName)
        {
            try
            {
                DirectorySearcher dssearch = new DirectorySearcher(domain);
                dssearch.Filter = string.Format("(&(objectClass=user)(sAMAccountName={0}))", userName);
                //LDAP://CN=TestRahul Bhatnagar,CN=Users,DC=krishnas,DC=com
                SearchResult sresult = dssearch.FindOne();
                if (sresult == null)
                {
                    return false;
                }
 
 
            }
            catch (Exception ex)
            {
                return false;
            }
 
            return true;
 
 
        }