ASP.NET Core, Ajax.Net, C#, VB.NET, MS SQL Server, Oracle, JavaScript, JQuery
Today's Date: 12/11/2018

Build a Silverlight Web Chatroom with Multiple Rooms and Private Chat - Part 2

Technologies Used: Silverlight 2, ASP.Net 3.5, WCF, C# 3.5, LINQ-to-SQL, MS SQL Server 2000/2005/2008

Introduction:

In part 1 we built a simple web chat using Silverlight 2. Now, we are going to add functionalities so that users are able to choose from multiple chat rooms as well as chat privately with other users. See the revised snapshot of the Silverlight Web Chat.

Silverlight 2 Chatroom

Requirements:

We will add a way for users to choose from a list of chatrooms to enter. A private chat between another user will also be established. The old requirements are still in effect which is listed below: Database

We will still use our the database with an additional field on the PrivateMessage table as shown below. See Part 1 for the table descriptions. The additional PrivateMessage table description is shown below.

Database Structure Newly Added XAML Files

Easily enough, because we started using XAML files based on their functionality in Part 1, we simply need to add two (2) new files; Rooms.xaml and PrivateChat.xaml. Login Changes

There is a very minor change in our login mechanism (Login.xaml.cs).

1. When the user is authenticated, we save this user to the LoggedInUser table as shown in lines 81-82. Notice that the only information we're passing is the userID, because this user have not chosen a room just yet. Line 82 (Login.xaml.cs) calls a new method in the ILinqChatService interface:

   39     [OperationContract]
   40     void LogInUser(int userID);


As usual, this method is implemented in the LinqChatService service.

  157    void ILinqChatService.LogInUser(int userID)
  158    {
  159        // login the user
  160        LinqChatDataContext db = new LinqChatDataContext();
  161 
  162         LoggedInUser loggedInUser = new LoggedInUser();
  163         loggedInUser.UserID = userID;
  164         db.LoggedInUsers.InsertOnSubmit(loggedInUser);
  165         db.SubmitChanges();
  166     }


2. Rather than going straight to the only room that was availble in Part 1, the user is redirected to the list of rooms page (Rooms.xaml) as shown in line 88.

   72     void proxy_UserExistCompleted(object sender, Silverlight2Chat.LinqChatReference.UserExistCompletedEventArgs e)
   73     {
   74         if (e.Error == null)
   75         {
   76             int userID = e.Result;
   77 
   78             if (userID != -1)
   79             {
   80                 // save user to the login table
   81                 LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
   82                 proxy.LogInUserAsync(userID);
   83 
   84                 // go to the chatroom page
   85                 App app = (App)Application.Current;
   86                 app.UserID = userID;
   87                 app.UserName = TxtUserName.Text;
   88                 app.RedirectTo(new Rooms());
   89             }
   90             else
   91             {
   92                 TxtbNotfound.Visibility = Visibility.Visible; 
   93             }
   94         }
   95     }


Choose a Room

The interface to Rooms.xaml is very straight forward. It contains two (2) controls; a TextBlock used to hold the title, and a StackPanel that holds a list of available rooms stacked vertically.

Rooms.xaml

    1 <UserControl x:Class="Silverlight2Chat.Rooms"
    2     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    3     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    4     Width="600" Height="340">
    5     <Grid x:Name="LayoutRoot" Background="White" ShowGridLines="False">
    6         <Grid.RowDefinitions>
    7             <RowDefinition Height="10" />       <!-- padding -->
    8             <RowDefinition Height="38" />       <!-- title -->
    9             <RowDefinition Height="10" />       <!-- padding -->
   10             <RowDefinition Height="*" />        <!-- rooms -->
   11             <RowDefinition Height="10" />       <!-- padding -->
   12         </Grid.RowDefinitions>
   13 
   14         <Grid.ColumnDefinitions>
   15             <ColumnDefinition Width="10" />     <!-- padding -->
   16             <ColumnDefinition Width="*" />      <!-- rooms -->
   17             <ColumnDefinition Width="10" />     <!-- padding -->
   18         </Grid.ColumnDefinitions>
   19 
   20         <TextBlock Text="Choose a Room" Grid.Row="1" Grid.Column="1" FontSize="22" Foreground="Navy" />
   21 
   22         <StackPanel x:Name="SpnlRoomList" Orientation="Vertical" Grid.Row="3" Grid.Column="1" />
   23     </Grid>
   24 </UserControl>


In the code file (Rooms.xaml.cs), we first check if the user is logged-in in line 26 by checking the UserName. We could just as easily have check the UserID instead of the UserName. Then we get the chatrooms in line 29. As mentioned in Part 1, because we are trying to get values from the client service proxy (WCF Service), we call the "Completed" event of the client proxy before calling the "Async" event, lines 35-36. The proxy_GetRoomsCompleted event retrieves all the available rooms from the Room table and assigns them to a HyperlinkButton, shown in lines 39-55. Notice that line 50 calls the Click event of the HyperlinkButton. When a user clicks one of the rooms listed in the chatroom list, the HyperlinkButton Click event simply "remembers" the RoomID and RoomName (lines 62-64), then redirects (line 67) the user to the Chatroom page (Chatroom.xaml). For more information on the basics of a WCF service, please read Part 1.

   20     public Rooms()
   21     {
   22         InitializeComponent();
   23 
   24         App app = (App)Application.Current;
   25 
   26         if (String.IsNullOrEmpty(app.UserName))
   27             app.RedirectTo(new Login());
   28 
   29         GetChatRooms();  
   30     }
   31 
   32     private void GetChatRooms()
   33     {
   34         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
   35         proxy.GetRoomsCompleted += new EventHandler<Silverlight2Chat.LinqChatReference.GetRoomsCompletedEventArgs>(proxy_GetRoomsCompleted);
   36         proxy.GetRoomsAsync();
   37     }
   38 
   39     void proxy_GetRoomsCompleted(object sender, Silverlight2Chat.LinqChatReference.GetRoomsCompletedEventArgs e)
   40     {
   41         if (e.Error == null)
   42         {
   43             ObservableCollection<LinqChatReference.RoomContract> rooms = e.Result;
   44 
   45             foreach (var room in rooms)
   46             {
   47                 HyperlinkButton linkButton = new HyperlinkButton();
   48                 linkButton.Name = room.RoomID.ToString();
   49                 linkButton.Content = room.Name;
   50                 linkButton.Click += new RoutedEventHandler(linkButton_Click);
   51 
   52                 SpnlRoomList.Children.Add(linkButton);
   53             }
   54         }
   55     }
   56 
   57     void linkButton_Click(object sender, RoutedEventArgs e)
   58     {
   59         HyperlinkButton linkButton = sender as HyperlinkButton;
   60 
   61         // assign the room 
   62         App app = (App)Application.Current;
   63         app.RoomID = Convert.ToInt32(linkButton.Name);
   64         app.RoomName = linkButton.Content.ToString();
   65 
   66         // redirect
   67         app.RedirectTo(new Chatroom());
   68     }


Chatroom Page

As you probably have already noticed, there is also a very minor revision in the GUI (graphical user interface) of the Chatroom.xaml page. The GUI revision mostly have nothing to do with functionality. The logged-in UserName was moved on top of the title in a StackPanel, and is now colored gray, line 25. A "Choose Other Room" button is added (line 30) on top of the Log Out button, also in a StackPanel. Notice that we are using a simple StackPanel (lines 43-44) for the list of users instead of an ItemsControl data template control as compared to what we used in Part 1, I will explain why later on in this article.

    1     <UserControl x:Class="Silverlight2Chat.Chatroom"
    2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    4         Width="600" Height="346">
    5         <Grid x:Name="LayoutRoot" Background="White" ShowGridLines="False" Loaded="LayoutRoot_Loaded">
    6             <Grid.RowDefinitions>
    7                 <RowDefinition Height="10" />       <!-- padding -->
    8                 <RowDefinition Height="46" />       <!-- title -->
    9                 <RowDefinition Height="10" />       <!-- padding -->
   10                 <RowDefinition Height="*" />        <!-- messages, userlist -->
   11                 <RowDefinition Height="10" />       <!-- padding -->       
   12                 <RowDefinition Height="26" />       <!-- message text box, send button -->
   13                 <RowDefinition Height="10" />       <!-- padding -->
   14             </Grid.RowDefinitions>
   15 
   16             <Grid.ColumnDefinitions>
   17                 <ColumnDefinition Width="10" />     <!-- padding -->
   18                 <ColumnDefinition Width="*" />      <!-- messages, message text box-->
   19                 <ColumnDefinition Width="10" />     <!-- padding -->
   20                 <ColumnDefinition Width="120" />    <!-- user list, send button-->
   21                 <ColumnDefinition Width="10" />     <!-- padding -->
   22             </Grid.ColumnDefinitions>
   23 
   24             <StackPanel Orientation="Vertical" Grid.Row="1" Grid.Column="1">
   25                 <TextBlock x:Name="TxtbLoggedInUser" FontSize="10" Foreground="Gray" FontWeight="Bold" Margin="0,0,0,4" />
   26                 <TextBlock x:Name="TxtbRoomName"  FontSize="24" Foreground="Navy" />    
   27             </StackPanel>
   28 
   29             <StackPanel Orientation="Vertical" Grid.Row="1" Grid.Column="3">
   30                 <Button x:Name="BtnChooseRoom" Content="Choose Other Room" FontSize="10" Click="BtnChooseRoom_Click" Margin="0,0,0,4" />
   31                 <Button x:Name="BtnLogOut" Content="Log Out" FontSize="10" Click="BtnLogOut_Click" />
   32             </StackPanel>
   33 
   34             <ScrollViewer x:Name="SvwrMessages" Grid.Row="3" Grid.Column="1" 
   35                           HorizontalScrollBarVisibility="Hidden" 
   36                           VerticalScrollBarVisibility="Visible" BorderThickness="2">
   37                 <StackPanel x:Name="SpnlMessages" Orientation="Vertical" />
   38             </ScrollViewer>
   39 
   40             <ScrollViewer x:Name="SvwrUserList" Grid.Row="3" Grid.Column="3" 
   41                           HorizontalScrollBarVisibility="Auto" 
   42                           VerticalScrollBarVisibility="Auto" BorderThickness="2">
   43                 <StackPanel x:Name="SpnlUserList" Orientation="Vertical">
   44                 </StackPanel>
   45             </ScrollViewer>
   46 
   47             <StackPanel Orientation="Horizontal" Grid.Row="5" Grid.Column="1" >
   48                 <TextBox x:Name="TxtMessage" TextWrapping="Wrap" KeyDown="TxtMessage_KeyDown"  
   49                      ScrollViewer.VerticalScrollBarVisibility="Visible" 
   50                      ScrollViewer.HorizontalScrollBarVisibility="Disabled"
   51                      Width="360"
   52                      BorderThickness="2" Margin="0,0,10,0"/>  
   53 
   54                 <ComboBox x:Name="CbxFontColor" Width="80">
   55                     <ComboBoxItem Content="Black" Foreground="White" Background="Black" IsSelected="True" />
   56                     <ComboBoxItem Content="Red" Foreground="White" Background="Red" />
   57                     <ComboBoxItem Content="Blue" Foreground="White" Background="Blue" />
   58                 </ComboBox>
   59             </StackPanel>
   60 
   61             <Button x:Name="BtnSend" Content="Send" Grid.Row="5" Grid.Column="3" Click="BtnSend_Click" />
   62         </Grid>
   63     </UserControl>


Most of the changes here were done to support private messages to other users as well as leaving this room to choose another room. With that said, we will dive right into the intricacies of chatting with other users privately.

1. Getting the Users: As I mentioned above, we changed the ItemsControl to a simple StackPanel that holds the list of users. One of the main reason is that, we want to be able to show all users as HyperlinkButton(s) besides the current logged-in user, which is you (lines 77-107). Simple enough, the idea is; you don't want to click your own name and accidentally chat with your own self.

   64     void proxy_GetUsersCompleted(object sender, Silverlight2Chat.LinqChatReference.GetUsersCompletedEventArgs e)
   65     {
   66         if (e.Error == null)
   67         {
   68             ObservableCollection<LinqChatReference.UserContract> users = e.Result;
   69             SpnlUserList.Children.Clear();
   70 
   71             foreach (var user in users)
   72             {
   73                 // show the current user as a non-clickable text only
   74                 // all other users should be hyperlinks
   75                 App app = (App)Application.Current;
   76 
   77                 if (user.UserID == app.UserID)
   78                 {
   79                     TextBlock tb = new TextBlock();
   80                     tb.Text = user.UserName;
   81                     tb.Foreground = new SolidColorBrush(Colors.Black);
   82                     tb.FontWeight = FontWeights.Bold;
   83 
   84                     SpnlUserList.Children.Add(tb);
   85                 }
   86                 else
   87                 {
   88                     HyperlinkButton hb = new HyperlinkButton();
   89                     hb.Content = user.UserName;
   90 
   91                     // build the absolute url
   92                     Uri url = System.Windows.Browser.HtmlPage.Document.DocumentUri;
   93                     string link = url.OriginalString;
   94                     int lastSlash = link.LastIndexOf('/') + 1;
   95                     link = link.Remove(lastSlash, link.Length - lastSlash) +
   96                         "Chatroom.aspx?fromuserid=" + app.UserID.ToString() +
   97                         "&fromusername=" + app.UserName +
   98                         "&touserid=" + user.UserID +
   99                         "&tousername=" + user.UserName +
  100                         "&isinvited=false";
  101 
  102                     // build the hyperlink
  103                     hb.TargetName = "_blank";
  104                     hb.NavigateUri = new Uri(link);
  105 
  106                     SpnlUserList.Children.Add(hb);
  107                 }  
  108             }
  109         }
  110     }


To chat with someone privately, I want to be able to open a new browser when I click a user on the user list. Currently, Silverlight's HyperlinkButton control can only be assigned an absolute URL. So to open up a new browser, we manipulate the current URL in the browser (lines 92-100 above) to build a link for each of the users. Notice in line 96 above that when this user is clicked, it will open the "Chatroom.aspx" ASP.Net page. This is because, like we talked about in Part 1, all the XAML user controls are going to be hosted by only one (1) ASP.Net page, and that page is the Chatroom.aspx page. Because a new browser means new instance of the chat application, the very first XAML user control that we encounter is the App.xaml. So now, how do we load the PrivateChat.xaml user control? We certainly don't want to enter a username and password each time we click another user to chat privately with them.

That is why we have a few querystring key/value pairs that are assigned to each user link seen in lines 96-100 above, like the "fromusername", "touserid", etc. We will use the respective values to sign-in the user automatically in the App.xaml user control. The "isinvited" key in line 100 simply states that you are the one inviting the other user to chat privately, and NOT the one being invited, isinvited=false;. I'll talk more about how we use this value later on.

Let's jump to the App.xaml user control to see how this process works. You will notice that we added a few public properties to hold and store our application-wide values. By looking at the highlighted code below, you can guess right away that the querystring key/value pairs shown in the HyperlinkButton (above), in the users list inside Chatroom.xaml user control are directly related.

   17     public int UserID { get; set; }
   18     public string UserName { get; set; }
   19     public int ToUserID { get; set; }
   20     public string ToUserName { get; set; }
   21     public DateTime TimeUserJoined { get; set; }
   22     public int RoomID { get; set; }
   23     public string RoomName { get; set; }
   24     public bool IsInvited { get; set; }
   25     public DateTime TimeUserSentInviation { get; set; }


Lines 64-69 below retrieves the key/value pairs from the querystring and then assigns them to the public properties of the App.xaml user control. To load the PrivateChat user control instead of the Login user control, we simply check at least one value from the url, indicating that this user has opened a private chat window. In this case, we're just checking the "fromusername" key shown in line 61. Lines 43-53 determines what XAML user control to load.

   38     private void Application_Startup(object sender, StartupEventArgs e)
   39     {
   40         this.RootVisual = rootGrid;
   41 
   42         // check if it's a private chat request
   43         if (IsPrivateChatRequest())
   44         {
   45             // open private chat instead of login page
   46             rootGrid.Children.Add(new PrivateChat());
   47         }
   48         else
   49         {
   50             // start at the login page
   51             // this.RootVisual = rootGrid;
   52             rootGrid.Children.Add(new Login());
   53         }
   54     }
   55 
   56     private bool IsPrivateChatRequest()
   57     {
   58         Uri uri = System.Windows.Browser.HtmlPage.Document.DocumentUri;
   59         IDictionary<string, string> queryString = System.Windows.Browser.HtmlPage.Document.QueryString;
   60 
   61         if (uri.ToString().Contains("fromusername"))
   62         {
   63             // set all the app wide variables
   64             App app = (App)Application.Current;
   65             app.UserID = Convert.ToInt32(queryString["fromuserid"]);
   66             app.UserName = queryString["fromusername"];
   67             app.ToUserID = Convert.ToInt32(queryString["touserid"]);
   68             app.ToUserName = queryString["tousername"];
   69             app.IsInvited = Convert.ToBoolean(queryString["isinvited"]);
   70 
   71             try
   72             {
   73                 app.TimeUserSentInviation = Convert.ToDateTime(queryString["timeusersentinvitation"]);    
   74             }
   75             catch { } 
   76 
   77             return true;
   78         }
   79         else
   80         {
   81             return false;
   82         }
   83     }


2. Responding to a Private Chat Invitation. Now back to the Chatroom.xaml user control. We just talked about the process of opening a private chat window so that you can invite another user to chat with you privately. At this point, you have not sent an invitation yet, you just opened the private chat window. You send an invitation to chat as soon as you send your first message to the other user. Let me talk about this process later when we get to the PrivateChat user control part of the article. For now, I will talk about how the other user (the one you're inviting to chat privately) can respond to your invitation.

We check the private message invitations from other users to you on the TimerControl's Tick event. In this event we call the GetPrivateMessages method to check for any invitation. This of course calls our WCF service via a client proxy as discussed above.

  261     void TimerTick(object sender, EventArgs e)
  262     {
  263         GetMessages();
  264         GetUsers();
  265         GetPrivateMessages();
  266     }
  267 
  268     private void GetPrivateMessages()
  269     {
  270         // get the private message invitations sent to me by other chatters
  271         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
  272         proxy.GetPrivateMessageInvitesCompleted += new EventHandler<Silverlight2Chat.LinqChatReference.GetPrivateMessageInvitesCompletedEventArgs>(proxy_GetPrivateMessageInvitesCompleted);
  273         proxy.GetPrivateMessageInvitesAsync(_userID);
  274     }


The implementation of getting the private message invitations is shown below, and can be found along with the other implementations of the ILinqChatService interface, in the LinqChatService.svc service.

  275     List<PrivateMessageContract> ILinqChatService.GetPrivateMessageInvites(int toUserID)
  276     {
  277         List<PrivateMessageContract> pmContracts = new List<PrivateMessageContract>();
  278         LinqChatDataContext db = new LinqChatDataContext();
  279 
  280         var pvtMessages = from pm in db.PrivateMessages
  281                           where pm.ToUserID == toUserID
  282                           select new { pm.PrivateMessageID, pm.UserID, pm.User.Username, pm.ToUserID, pm.TimeUserSentInvitation };
  283 
  284         if (pvtMessages.Count() > 0)
  285         {
  286             foreach(var privateMessage in pvtMessages)
  287             {
  288                 PrivateMessageContract pmc = new PrivateMessageContract();
  289                 pmc.PrivateMessageID = privateMessage.PrivateMessageID;
  290                 pmc.UserID = privateMessage.UserID;
  291                 pmc.UserName = privateMessage.Username;
  292                 pmc.ToUserID = privateMessage.ToUserID;
  293                 pmc.TimeUserSentInvitation = privateMessage.TimeUserSentInvitation;
  294 
  295                 pmContracts.Add(pmc);
  296             }
  297         }
  298 
  299         return pmContracts;
  300     }


Each invitation will cause to show a Silverlight Popup control as shown in the image below.

Private Chat Invitation

The code that builds this Popup control for each invitation and causes the pop-up to show can be found in the GetPrivateMessage Completed event shown below. I know what you're thinking, "it takes this much code to show a very simple pop-up control?", the answer is Yes. What's even more amazing is each of the buttons, the Close and Chat Now buttons have their own Click event code, so that makes the code even longer, line 346 and 357. The code shown below simply adds a TextBlock control, a dummy Chat Now Button control, a Close Button control and a Chat Now HyperlinkButton control to the Grid control which is a Child of the Popup control. The Popup control is set to show or set to be visible as shown in line 285.

The dummy Chat Now Button control is used as a "background" control to the real Chat Now HyperlinkButton control so that we can make the HyperlinkButton control look like a button. This is just my preference, you could have as easily assigned the HyperlinkButton control's Content property to show a button, or even design the HyperlinkButton to show like a button. You can see that both the Button and HyperlinkButton are located in the same spot, lines 316 and 328.

  276     void proxy_GetPrivateMessageInvitesCompleted(object sender, Silverlight2Chat.LinqChatReference.GetPrivateMessageInvitesCompletedEventArgs e)
  277     {
  278         ObservableCollection<LinqChatReference.PrivateMessageContract> invitations = e.Result;
  279 
  280         foreach (var invitation in invitations)
  281         {
  282             Popup popUp = new Popup();
  283             Grid grid = new Grid();
  284             popUp.Child = grid;
  285             popUp.IsOpen = true;
  286             popUp.Name = "PopUpInvitation" + invitation.PrivateMessageID.ToString();
  287 
  288             // add popup to the root grid
  289             LayoutRoot.Children.Add(popUp);
  290 
  291             grid.Width = 200;
  292             grid.Height = 100;
  293             grid.HorizontalAlignment = HorizontalAlignment.Center;
  294 
  295             // pop-up border
  296             Border border = new Border();
  297             border.BorderBrush = new SolidColorBrush(Colors.Black);
  298             border.BorderThickness = new Thickness(2);
  299             border.CornerRadius = new CornerRadius(8);
  300             border.Background = new SolidColorBrush(Colors.White);
  301 
  302             // pop-up text
  303             App app = (App)Application.Current;
  304 
  305             TextBlock textBlock = new TextBlock();
  306             textBlock.Text = app.UserName  + " wants to chat privately.";
  307             textBlock.HorizontalAlignment = HorizontalAlignment.Center;
  308             textBlock.VerticalAlignment = VerticalAlignment.Top;
  309             textBlock.Margin = new Thickness(8);
  310 
  311             // accept button - background only
  312             Button btnAccept = new Button();
  313             btnAccept.Width = 100;
  314             btnAccept.Height = 24;
  315             btnAccept.HorizontalAlignment = HorizontalAlignment.Left;
  316             btnAccept.VerticalAlignment = VerticalAlignment.Bottom;
  317             btnAccept.Margin = new Thickness(8);
  318 
  319             // accept hyperlink - put on top of the accept button
  320             HyperlinkButton hpBtn = new HyperlinkButton();
  321             hpBtn.Name = "HbtnChatNow" + invitation.PrivateMessageID.ToString();
  322             hpBtn.Width = 100;
  323             hpBtn.Height = 22;
  324             hpBtn.Content = "     Chat Now    ";
  325             hpBtn.Foreground = new SolidColorBrush(Colors.Green);
  326             hpBtn.Background = new SolidColorBrush(Colors.Transparent);
  327             hpBtn.HorizontalAlignment = HorizontalAlignment.Left;
  328             hpBtn.VerticalAlignment = VerticalAlignment.Bottom;
  329             hpBtn.Margin = new Thickness(8);
  330 
  331             // build the absolute url
  332             Uri url = System.Windows.Browser.HtmlPage.Document.DocumentUri;
  333             string link = url.OriginalString;
  334             int lastSlash = link.LastIndexOf('/') + 1;
  335             link = link.Remove(lastSlash, link.Length - lastSlash) +
  336                 "Chatroom.aspx?fromuserid=" + app.UserID.ToString() +
  337                 "&fromusername=" + app.UserName +
  338                 "&touserid=" + invitation.UserID +
  339                 "&tousername=" + invitation.UserName +
  340                 "&isinvited=true" +
  341                 "&timeusersentinvitation=" + invitation.TimeUserSentInvitation.ToString();
  342 
  343             // build the hyperlink
  344             hpBtn.TargetName = "_blank";
  345             hpBtn.NavigateUri = new Uri(link);
  346             hpBtn.Click += new RoutedEventHandler(hpBtn_Click);
  347 
  348             // close button
  349             Button btnClose = new Button();
  350             btnClose.Name = "BtnClose" + invitation.PrivateMessageID.ToString();
  351             btnClose.Width = 50;
  352             btnClose.Height = 24;
  353             btnClose.Content = "Close";
  354             btnClose.HorizontalAlignment = HorizontalAlignment.Right;
  355             btnClose.VerticalAlignment = VerticalAlignment.Bottom;
  356             btnClose.Margin = new Thickness(8);
  357             btnClose.Click += new RoutedEventHandler(btnClose_Click);
  358 
  359             // add to grid
  360             grid.Children.Add(border);
  361             grid.Children.Add(textBlock);
  362             grid.Children.Add(btnAccept);
  363             grid.Children.Add(hpBtn);
  364             grid.Children.Add(btnClose);
  365 
  366             // delete private message invation from database
  367             LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
  368             proxy.DeletePrivateMessageAsync(invitation.PrivateMessageID);
  369         }
  370     }


The close Button and the chat now HyperlinkButton pretty much does the same thing when you click on them as shown in their respective Click events below. They simply get the name of the Popup control to close and then closes them by doing popUp.IsOpen = false. But the chat now HyperlinkButton also opens up the PrivateChat.xaml user control in the browser, much like the same way we opened up a new browser when we invited someone to chat privately with us earlier in this article. This is because we used pretty much the same code as shown in lines 332-341 shown above, the only differences are; the value on the "isinvited" which is "true" in line 340 (signifies that you're the one being invited to chat privately), and another key/value pair is added in line 341, "timeusersentinvitation", which signifies the time the other user sent you the invitation to chat privately. We will use the value from the "timeusersentinvitation" to get all the private messages from the time the the other user sent you an invitation. I will talk more about this later.

  372     void hpBtn_Click(object sender, RoutedEventArgs e)
  373     {
  374         // get the name of the pop-up to close
  375         // based from the name of the hyperlink button
  376         HyperlinkButton button = sender as HyperlinkButton;
  377         string privateMessageID = button.Name.Replace("HbtnChatNow", "");
  378 
  379         Popup popUp = (Popup)LayoutRoot.FindName("PopUpInvitation" + privateMessageID);
  380         popUp.IsOpen = false;
  381     }
  382 
  383     void btnClose_Click(object sender, RoutedEventArgs e)
  384     {
  385         // get the name of the pop-up to close
  386         // based from the name of the button
  387         Button button = sender as Button;
  388         string privateMessageID = button.Name.Replace("BtnClose", "");
  389 
  390         Popup popUp = (Popup) LayoutRoot.FindName("PopUpInvitation" + privateMessageID);
  391         popUp.IsOpen = false;
  392     }


PrivateChat User Control

Private Chat Window

As you can see, this control looks just like the Chatroom user control, except that some controls are ommited such as the title, log-out button, etc. And because of the similarities, the way we send messages or receive messages works the same way, except we're only sending them to one user. Shown below is the PrivateChat user control GUI code.

    1     <UserControl x:Class="Silverlight2Chat.PrivateChat"
    2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    4         Width="440" Height="280">
    5         <Grid x:Name="LayoutRoot" Background="White" ShowGridLines="False" Loaded="LayoutRoot_Loaded">
    6             <Grid.RowDefinitions>
    7                 <RowDefinition Height="10" />       <!-- padding -->
    8                 <RowDefinition Height="*" />        <!-- messages -->
    9                 <RowDefinition Height="10" />       <!-- padding -->       
   10                 <RowDefinition Height="26" />       <!-- message text box, send button -->
   11                 <RowDefinition Height="10" />       <!-- padding -->
   12             </Grid.RowDefinitions>
   13 
   14             <Grid.ColumnDefinitions>
   15                 <ColumnDefinition Width="10" />     <!-- padding -->
   16                 <ColumnDefinition Width="*" />      <!-- messages, message text box-->
   17                 <ColumnDefinition Width="10" />     <!-- padding -->
   18             </Grid.ColumnDefinitions>
   19 
   20             <ScrollViewer x:Name="SvwrMessages" Grid.Row="1" Grid.Column="1" 
   21                           HorizontalScrollBarVisibility="Hidden" 
   22                           VerticalScrollBarVisibility="Visible" BorderThickness="2">
   23                 <StackPanel x:Name="SpnlMessages" Orientation="Vertical" />
   24             </ScrollViewer>
   25 
   26             <StackPanel Orientation="Horizontal" Grid.Row="3" Grid.Column="1" >
   27                 <TextBox x:Name="TxtMessage" TextWrapping="Wrap" KeyDown="TxtMessage_KeyDown"  
   28                      ScrollViewer.VerticalScrollBarVisibility="Visible" 
   29                      ScrollViewer.HorizontalScrollBarVisibility="Disabled"
   30                      Width="280"
   31                      BorderThickness="2" Margin="0,0,10,0"/>  
   32 
   33                 <ComboBox x:Name="CbxFontColor" Width="60" Margin="0,0,10,0">
   34                     <ComboBoxItem Content="Black" Foreground="White" Background="Black" IsSelected="True" />
   35                     <ComboBoxItem Content="Red" Foreground="White" Background="Red" />
   36                     <ComboBoxItem Content="Blue" Foreground="White" Background="Blue" />
   37                 </ComboBox>
   38 
   39                 <Button x:Name="BtnSend" Content="Send" Click="BtnSend_Click" Width="60" />
   40             </StackPanel>
   41 
   42         </Grid>
   43     </UserControl>


1. Invite Another User to Chat Privately. When you clicked one of the users listed in the Chatroom.xaml page, this private chat window appears. To invite someone to chat privately you first need to send at least one message to the other user. Lines 201-205.

  185     private void BtnSend_Click(object sender, RoutedEventArgs e)
  186     {
  187         SendMessage();
  188     }
  189 
  190     private void SendMessage()
  191     {
  192         if (!String.IsNullOrEmpty(TxtMessage.Text))
  193         {
  194             InsertMessage();
  195             GetPrivateMessages();
  196 
  197             // send an invitation to chat only if you're the one that
  198             // is sending the invitation, this means that you clicked
  199             // one of the users in the user list in the main chat
  200             // and did not click the invitation to chat pop up
  201             if (_isInvitationToChatSent == false && _isInvited == false)
  202             {
  203                 InviteOtherUserToChat();
  204                 _isInvited = true;
  205             }
  206         }
  207     }


The method called in line 203 above is shown below. Because we are not expecting anything to be returned from the WCF service shown below, we need not call the Completed event of the InsertPrivateMessageInvite object. In short, we only need to call the "Async" method of this client proxy.

  214     private void InviteOtherUserToChat()
  215     {
  216         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
  217         proxy.InsertPrivateMessageInviteAsync(_fromUserID, _toUserID);
  218     }


The Async WCF call in line 217 above calls the WCF service method found in LinqChatService.cs. Notice that the async call above and the method below have the same signature. The service below inserts an entry in the PrivateMessage table.

  243     void ILinqChatService.InsertPrivateMessageInvite(int userID, int toUserID)
  244     {
  245         // first check if an invitation to chat has already
  246         // been sent to the particular user "toUserID"
  247         LinqChatDataContext db = new LinqChatDataContext();
  248 
  249         var count = (from pvtm in db.PrivateMessages
  250                      where pvtm.UserID == userID &&
  251                      pvtm.ToUserID == toUserID
  252                      select new { pvtm.PrivateMessageID }).Count();
  253 
  254         if (count == 0)
  255         {
  256             // no invitation was found
  257             PrivateMessage pm = new PrivateMessage();
  258             pm.UserID = userID;
  259             pm.ToUserID = toUserID;
  260             pm.TimeUserSentInvitation = DateTime.Now;
  261 
  262             db.PrivateMessages.InsertOnSubmit(pm);
  263 
  264             try
  265             {
  266                 db.SubmitChanges();
  267             }
  268             catch (Exception)
  269             {
  270                 throw;
  271             }
  272         } 
  273     }


2. Sending Private Messages. In the chatroom, we're getting all the messages displayed from all the users that are chatting. Here, we're only supposed to get messages between the two users privately chatting with each other. This is simple enough to solve. In the Chatroom.xaml user control when we insert a message in the Message table, the "_toUserID" is set to null, here we simply set that value to the user that we're trying to chat with. The _toUserID value is set in this user control's constructor, which is retrieved from the App.xaml's public properties.

   19     DispatcherTimer timer;
   20     private bool _isTimerStarted;
   21     private bool _isWithBackground = false;
   22     private int _lastMessageId = 0;
   23     private int _fromUserID;
   24     private int _toUserID;
   25     private bool _isInvited;
   26     private bool _isInvitationToChatSent = false;
   27     private DateTime _timeUserSentInvitation;
   28 
   29     public PrivateChat()
   30     {
   31         InitializeComponent();
   32 
   33         App app = (App)Application.Current;
   34 
   35         if (String.IsNullOrEmpty(app.UserName))
   36         {
   37             app.RedirectTo(new Login());
   38         }
   39         else
   40         {
   41             _fromUserID = app.UserID;
   42             _toUserID = app.ToUserID;
   43             _isInvited = app.IsInvited;
   44 
   45             if (_isInvited)
   46                 _timeUserSentInvitation = app.TimeUserSentInviation;
   47             else
   48                 _timeUserSentInvitation = DateTime.Now;
   49         }
   50     }


This makes it very simple to send the message to the other user.

   68     private void InsertMessage()
   69     {
   70         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
   71         proxy.InsertMessageAsync(null, _fromUserID, _toUserID, TxtMessage.Text, CbxFontColor.SelectionBoxItem.ToString());
   72     }


3. Getting Private Messages. Just like when we're sending messages to another user privately, we need to populate the _fromUserID and _toUserID variables to retrieve just the messages meant for this exclusive chat users. Another piece of information we need to populate from the very first time the "inviting" user sent an invitation to chat privately is assigned to the _timeUserSentInvitation variable. This way we will only retrieve the messages from that time on and above.

   74     private void GetPrivateMessages()
   75     {
   76         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
   77         proxy.GetPrivateMessagesCompleted += new EventHandler<Silverlight2Chat.LinqChatReference.GetPrivateMessagesCompletedEventArgs>(proxy_GetPrivateMessagesCompleted);
   78         proxy.GetPrivateMessagesAsync(_timeUserSentInvitation, _lastMessageId, _fromUserID, _toUserID);
   79     }


The GetPrivateMessagesCompleted event here does the same thing as the GetMessagesCompleted event in the Chatroom.xaml user control so I'm not going to spend any time explaining it. For more information on the Completed event see Part 1. The Async proxy code above calls the WCF service GetPrivateMessages located in LinqChatService.svc.cs. One thing I would like to stress out is the way we built the query especially the code shown in lines 68-69. We are retrieving all messages sent by either user chatting privately which is "sent to" either user chatting privately.

   62     List<MessageContract> ILinqChatService.GetPrivateMessages(DateTime timeUserSentInvitation, int messageID, int fromUserId, int toUserId)
   63     {
   64         LinqChatDataContext db = new LinqChatDataContext();
   65 
   66         var messages = (from m in db.Messages
   67                         where 
   68                         ((m.UserID == fromUserId && m.ToUserID == toUserId) || 
   69                         (m.ToUserID == fromUserId && m.UserID == toUserId)) && 
   70                         m.TimeStamp >= timeUserSentInvitation &&
   71                         m.MessageID > messageID 
   72                         orderby m.TimeStamp ascending
   73                         select new { m.MessageID, m.Text, m.User.Username, m.TimeStamp, m.Color });
   74 
   75         List<MessageContract> messageContracts = new List<MessageContract>();
   76 
   77         foreach (var message in messages)
   78         {
   79             MessageContract messageContract = new MessageContract();
   80             messageContract.MessageID = message.MessageID;
   81             messageContract.Text = message.Text;
   82             messageContract.UserName = message.Username;
   83             messageContract.Color = message.Color;
   84             messageContracts.Add(messageContract);
   85         }
   86 
   87         return messageContracts;
   88     }


4. Resizing the Private Chat Window

Silverlight 2 unfornately does not have a functionality to open a new window in a specified size at the time of this writing. Remember that we're hosting all the XAML user controls using just one ASP.net page. So to dynamically resize this ASP.net page only when the PrivateChat.xaml user control is loaded, we need some kind of indication, somehow passing the information from a XAML user control to an ASP.Net page. Luckilly enough, we can write some hack in JavaScript to to just this. Using JavaScript, we can examine at least one querystring key/value pair from the Chatroom.aspx page. In this case, we are going to check for the "fromusername" key. If the key is there, we resize the window (Chatroom.aspx) to 640 x 460.

    9    <script type="Text/javascript">

   10         window.onload = function()

   11         {

   12             ResizeWindow();

   13             document.getElementById('Xaml1').focus();

   14         }

   15 

   16         function ResizeWindow()

   17         {

   18             var fromusername = GetQueryString("fromusername");

   19 

   20             if (fromusername != null)

   21             {

   22                 // resize the screen

   23                 window.resizeTo(640, 460);

   24             }   

   25         }

   26 

   27         function GetQueryString(variable)

   28         {

   29             var query = window.location.search.substring(1);

   30             var vars = query.split("&");

   31 

   32             for (var i = 0; i < vars.length; i++)

   33             {

   34                 var pair = vars[i].split("=");

   35 

   36                 if (pair[0] == variable)

   37                     return pair[1];

   38             }

   39         }

   40     </script>



Choosing Other Rooms

You need to leave your current room to enter another room. You can click the button with the text "Choose Other Room" located in the Chatroom.xaml user control. The click event is shown below.

  406     private void BtnChooseRoom_Click(object sender, RoutedEventArgs e)
  407     {
  408         timer.Stop();
  409         App app = (App)Application.Current;
  410 
  411         // leave the room to choose another room
  412         LinqChatReference.LinqChatServiceClient proxy = new LinqChatReference.LinqChatServiceClient();
  413         proxy.LeaveRoomAsync(_userID, _roomId, app.UserName);
  414 
  415         // redirect to the rooms page
  416         app.RedirectTo(new Rooms());
  417     }


The proxy client method above calls the WCF service method shown below. The only difference with this method and the Log Out method is that; Here we are only setting the RoomID = null in the LoggedInUser table, whereas in the Log Out method, we are totally deleting this user from the LoggedInUser table.

  194     void ILinqChatService.LeaveRoom(int userID, int roomID, string username)
  195     {
  196         // leave the room by setting room id = null
  197         LinqChatDataContext db = new LinqChatDataContext();
  198 
  199         var loggedInUser = (from l in db.LoggedInUsers
  200                             where l.UserID == userID
  201                             && l.RoomID == roomID
  202                             select l).SingleOrDefault();
  203 
  204         loggedInUser.RoomID = null;
  205         db.SubmitChanges();
  206 
  207         // insert user "left the room" text
  208         Message message = new Message();
  209         message.RoomID = roomID;
  210         message.UserID = userID;
  211         message.ToUserID = null;
  212         message.Text = username + " left the room.";
  213         message.Color = "Gray";
  214         message.TimeStamp = DateTime.Now;
  215 
  216         db.Messages.InsertOnSubmit(message);
  217         db.SubmitChanges();
  218     }


Because this is a Web Chat application, you could of course open several browsers, log-in in each browser, and then enter different rooms at the same time.

Last Words:

I hope that you learned something out of this article. I did not discuss the basics of WCF (Windows Communication Foundation), nor did I discuss the formatting of the messages in the chatroom because these and others can be found in Part 1. The article is meant for learning the processes of establishing a monitored private chat using Silverlight 2 and MS SQL Server. There are a lot of things that you can improve here. For example, to improve performance, you can change all calls to the database using Stored Procedures instead of Dynamic SQL. Rather than being too chatty, you can also combine calls to the database to make one trip instead of several trips like the methods found in the TimerTick event of the Chatroom.xaml user control.


Code Download: Click here to download the code

As always, the code and the article are provided "As Is", there is absolutely no warranties. Use at your own risk.

Happy Coding!!!

Date Created: Tuesday, March 17, 2009



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