how to send request notification for application using FBDialog in IOS?

Question

I am trying to send invitation to my Facebook friends through my application. I have friends list of my Facebook friends in my application, I used FBWeb-dialog to send invitation to my friends. After selection my friends to whom I want to send request I am sending request them and its working fine, but my problem is that they are not receiving any notification to their wall.

Can anybody tell me what should I do to notify them via notification?

NSMutableDictionary* params =   [NSMutableDictionary dictionaryWithObjectsAndKeys:[arrSelectedFriends componentsJoinedByString:@","], @"suggestions",nil];
            [FBWebDialogs presentRequestsDialogModallyWithSession:nil
                    message:@"User X” has invited you to join demoApp,Download the free app here."
                title:nil parameters:params
                handler:^(FBWebDialogResult result, NSURL *resultURL, NSError *error)
                {
                    if (error)
                    {
                        // Case A: Error launching the dialog or sending request.
                        NSLog(@"Error sending request.");
                    }
                    else
                    {
                        if (result == FBWebDialogResultDialogNotCompleted)
                        {
                        // Case B: User clicked the "x" icon
                            NSLog(@"User canceled request.");
                        } else {
                                NSLog(@"Request Sent.");
                        }
                    }
                }];