Handle events from DataTemplate in custom control

Question

I am writing a WPF client and have created a custom Chat control that will be used within the client, the Chat control comprises of a ChatClient that handles joining and leaving the Chat service and displaying a list of connected Users as per the following XAML:

<Style TargetType="{x:Type chat:ChatClient}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type chat:ChatClient}">
                <Grid Margin="0,0,0,0" Background="{StaticResource ChatClientBackgroundBrush}">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="200" />
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="135" />
                        <RowDefinition Height="*" />
                    </Grid.RowDefinitions>
                    <Grid Grid.Row="0" Margin="0,0,0,0" Background="{StaticResource ChatClientBackgroundBrush}">
                        <Grid.RowDefinitions>
                            <RowDefinition Height="100" />
                            <RowDefinition Height="32" />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>

                        <Border Grid.Column="0" Grid.Row="0" Height="100" Margin="0,0,0,0" Padding="1,1,1,0" BorderBrush="{StaticResource ChatClientAvatarBorderBrush}">
                            <Image Height="80" Width="80" Source="Cleo.Windows.Ui.Chat;component/Resources/noavatar.png" StretchDirection="Both" Stretch="Fill">
                                <Image.Clip>
                                    <EllipseGeometry Center="40,40" RadiusX="40" RadiusY="40" />
                                </Image.Clip>
                            </Image>
                        </Border>
                        <StackPanel Grid.Column="0" Grid.Row="1" Orientation="Horizontal">
                            <Ellipse Height="8" Width="8" Fill="{StaticResource ChatClientPresenceOnlineBrush}" Margin="6,-8,0,0" />
                            <TextBlock Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=CurrentPerson.Name}" Margin="8,0" Foreground="{StaticResource ChatClientTextBrush}"
                                       FontSize="16" />
                        </StackPanel>
                    </Grid>

                    <Border Grid.Row="1" BorderThickness="0,1,0,0" BorderBrush="{StaticResource ChatClientBorderBrush}">
                        <Grid Background="{StaticResource ChatClientBackgroundBrush}">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" MinHeight="100" />
                            </Grid.RowDefinitions>
                            <ScrollViewer x:Name="srcContacts" Grid.Row="0" Margin="0,0,0,0" VerticalScrollBarVisibility="Auto">
                                <StackPanel>
                                    <ItemsControl ItemsSource="{Binding Path=People, RelativeSource={RelativeSource AncestorType={x:Type chat:ChatClient}}}" x:Name="Contacts">
                                        <ItemsControl.ItemTemplate>
                                            <DataTemplate>
                                                <ContentControl>
                                                    <Border Style="{StaticResource IsMouseOver}">
                                                        <Grid>
                                                            <Grid.ColumnDefinitions>
                                                                <ColumnDefinition Width="40" />
                                                                <ColumnDefinition Width="*" />
                                                            </Grid.ColumnDefinitions>
                                                            <Grid.RowDefinitions>
                                                                <RowDefinition Height="*" />
                                                                <RowDefinition Height="*" />
                                                            </Grid.RowDefinitions>
                                                            <Border Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" VerticalAlignment="Top" Height="35" Width="35" Margin="5,0,0,0"
                                                                BorderBrush="{StaticResource ChatClientPresenceOnlineBrush}" BorderThickness="2" CornerRadius="15">
                                                                <Image Height="30" Width="30" Source="Cleo.Windows.Ui.Chat;component/Resources/noavatar.png" StretchDirection="Both" Stretch="Fill">
                                                                    <Image.Clip>
                                                                        <EllipseGeometry Center="15,15" RadiusX="15" RadiusY="15" />
                                                                    </Image.Clip>
                                                                </Image>
                                                            </Border>
                                                            <TextBlock Grid.Column="1" Grid.Row="0" Foreground="{StaticResource ChatClientTextBrush}" Padding="0" Margin="10,0,0,0" FontWeight="Bold"
                                                                   Text="{Binding Name}"></TextBlock>
                                                        </Grid>
                                                    </Border>
                                                </ContentControl>
                                            </DataTemplate>
                                        </ItemsControl.ItemTemplate>
                                    </ItemsControl>
                                </StackPanel>
                            </ScrollViewer>
                        </Grid>
                    </Border>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

This is defined in a ResourceDictionary in the Chat assembly and the ChatClient is added as a control to the main application window.

This is all great and when I run the application it connects to the chat server and I get a nice panel to the right of the main window with a list of connected users.

Ok, so my question is specifically related to the following part from the XAML above:

<ScrollViewer x:Name="srcContacts" Grid.Row="0" Margin="0,0,0,0" VerticalScrollBarVisibility="Auto">
    <StackPanel>
        <ItemsControl ItemsSource="{Binding Path=People, RelativeSource={RelativeSource AncestorType={x:Type chat:ChatClient}}}" x:Name="Contacts">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <ContentControl>
                        <Border Style="{StaticResource IsMouseOver}">
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="40" />
                                    <ColumnDefinition Width="*" />
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="*" />
                                </Grid.RowDefinitions>
                                <Border Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" VerticalAlignment="Top" Height="35" Width="35" Margin="5,0,0,0" BorderBrush="{StaticResource ChatClientPresenceOnlineBrush}" BorderThickness="2" CornerRadius="15">
                                    <Image Height="30" Width="30" Source="Cleo.Windows.Ui.Chat;component/Resources/noavatar.png" StretchDirection="Both" Stretch="Fill">
                                        <Image.Clip>
                                            <EllipseGeometry Center="15,15" RadiusX="15" RadiusY="15" />
                                        </Image.Clip>
                                    </Image>
                                </Border>
                                <TextBlock Grid.Column="1" Grid.Row="0" Foreground="{StaticResource ChatClientTextBrush}" Padding="0" Margin="10,0,0,0" FontWeight="Bold" Text="{Binding Name}"></TextBlock>
                            </Grid>
                        </Border>
                    </ContentControl>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </StackPanel>
</ScrollViewer>

In the above DataTemplate an item is created for each connected Person, I would like to know how I can handle the MouseDoubleClick event of the ContentControl from the ChatClient, so that the ChatClient will be responsible for creating the ChatWindow, examples would be good as still quite new to WPF.

I have been reading up on Attached Behaviors but struggling to understand how these would fit in to what I am looking to achieve which is that my ChatClient class has an event handler that is fired when I double click any item added within the DataTemplate.

Any suggestions on how to achieve this will be greatly received.

Answer 1

I recommend you to fire a Command on MouseDoubleClick event.

To connect a MouseDoubleClick event to a Command and pass ClientId to it, you can use somethings like this:

<ScrollViewer x:Name="srcContacts" Grid.Row="0" Margin="0,0,0,0" VerticalScrollBarVisibility="Auto">
    <StackPanel>
        <ItemsControl ItemsSource="{Binding Path=People, RelativeSource={RelativeSource AncestorType={x:Type chat:ChatClient}}}" x:Name="Contacts">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <ContentControl>

                         <!-- ــــInputBinding For Mouse LeftDoubleClickــــ -->
                         <ContentControl.InputBindings>
                              <MouseBinding Gesture="LeftDoubleClick"
                                            Command="{Binding RelativeSource={RelativeSource AncestorType=ItemsControl},Path=DataContext.ClientDoubleClickCommand}" 
                                            CommandParameter="{Binding ClientId}"/>
                         <ContentControl.InputBindings>
                         <!-- ــــــــــــــــــــــــــــــــــــــــ -->

                        <Border Style="{StaticResource IsMouseOver}">
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="40" />
                                    <ColumnDefinition Width="*" />
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="*" />
                                </Grid.RowDefinitions>
                                <Border Grid.Column="0" Grid.Row="0" Grid.RowSpan="2" VerticalAlignment="Top" Height="35" Width="35" Margin="5,0,0,0" BorderBrush="{StaticResource ChatClientPresenceOnlineBrush}" BorderThickness="2" CornerRadius="15">
                                    <Image Height="30" Width="30" Source="Cleo.Windows.Ui.Chat;component/Resources/noavatar.png" StretchDirection="Both" Stretch="Fill">
                                        <Image.Clip>
                                            <EllipseGeometry Center="15,15" RadiusX="15" RadiusY="15" />
                                        </Image.Clip>
                                    </Image>
                                </Border>
                                <TextBlock Grid.Column="1" Grid.Row="0" Foreground="{StaticResource ChatClientTextBrush}" Padding="0" Margin="10,0,0,0" FontWeight="Bold" Text="{Binding Name}"></TextBlock>
                            </Grid>
                        </Border>
                    </ContentControl>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </StackPanel>
</ScrollViewer>

Then you can simply define ClientDoubleClickCommand command in ClientChat class (like other members of it such as People ):

public class ChatClient: INotifyPropertyChanged
{
    //-------- Peopole property --------
    .
    .
    .

    //-------- ClientDoubleClickCommand --------
    ICommand clientDoubleClickCommand;
    public ICommand ClientDoubleClickCommand
    {
        get
        {
            return clientDoubleClickCommand ??
                (clientDoubleClickCommand = new MyCommand(DoThisOnDoubleClick, true));
        }
    }

    private void DoThisOnDoubleClick(object clientId)
    {
        // Write your target codes (on Mouse Left Double Click) here:
        throw new NotImplementedException();
    }

    //-------- OTHER PROPERTIES AND CODES OF CLASS--------
    .
    .
    .

}

// MyCommand Class: This class is a technique to implement commands easily
public class MyCommand: ICommand
{
    private readonly Action<object> _action;
    private readonly bool _canExecute;
    public MyCommand(Action<object> action, bool canExecute)
    {
        _action = action;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return _canExecute;
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        _action(parameter);
    }
}

public class People: INotifyPropertyChanged
{
   // ClientId Property:
    .
    .
    .

   // ClientName Property:
    .
    .
    .

   //-------- OTHER PROPERTIES AND CODES OF CLASS--------
    .
    .
    .

}

In this example, i assumed you have a ClientId property in your People class to keep id of each client.

Now you have a People property, it is a list of clients and you used it like this:

<ItemsControl ItemsSource="{Binding Path=People,........

On the other hand if the ItemsControl DataContext be »» ChatClient class then we have access to ClientDoubleClickCommand in it and access to ClientId in People class (by ItemsSource ) in the following line inside ItemsControl block:

<MouseBinding Gesture="LeftDoubleClick"
              Command="{Binding RelativeSource={RelativeSource AncestorType=ItemsControl},Path=DataContext.ClientDoubleClickCommand}" 
              CommandParameter="{Binding ClientId}"/>