private void RemoveHashKeys(string obj_type, List<string> keys, bool isAsync, RemoveHashKeysCallback callback, Object state)
        {
            var parameterList = new Dictionary<string, string> { { "method", "facebook.data.removeHashKeys" } };
            Utilities.AddRequiredParameter(parameterList, "obj_type", obj_type);
            Utilities.AddList(parameterList, "keys", keys);

            if (isAsync)
            {
                SendRequestAsync<data_removeHashKeys_response, bool>(parameterList, new FacebookCallCompleted<bool>(callback), state);
                return;
            }

            SendRequest(parameterList);
        }
 /// <summary>
 /// Delete multiple objects by a list of hash keys. 
 /// </summary>
 /// <example>
 /// <code>
 /// 
 /// </code>
 /// </example>
 /// <param name="obj_type">Object's type. This is required, so that different object types may use the same hash keys for different objects. </param>
 /// <param name="keys">A list of hash keys (string object identifier) to remove.</param>
 /// <param name="callback">The AsyncCallback delegate</param>
 /// <param name="state">An object containing state information for this asynchronous request</param>        
 public void RemoveHashKeysAsync(string obj_type, List<string> keys, RemoveHashKeysCallback callback, Object state)
 {
     RemoveHashKeys(obj_type, keys, true, callback, state);
 }