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Silverlight Invoke Commands

Posted by Mahadesh Mahalingappa Articles | Silverlight with C# August 11, 2011
In this article we are going to see how we can Invoke Commands in Silverlight.
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This article will help us understand how we can create simple commands and bind them to our Silverlight Controls.

Created a Simple Project as SLSimpleCommands .

Add a Child Window Control as shown below:

child window in silverlight

Let's create the Command now. Here I am creating a simple command which would open our child Window.

Our Command should implement the ICommand Interface.

namespace System.Windows.Input
{
   
// Summary:
    //     Defines the contract for commanding, using the same contract as used in WPF.
    public interface ICommand
    {
       
// Summary:
        //     Occurs when changes occur that affect whether the command should execute.
        event EventHandler CanExecuteChanged;
 
       
// Summary:
        //     Defines the method that determines whether the command can execute in its
        //     current state.
        //
        // Parameters:
        //   parameter:
        //     Data used by the command. If the command does not require data to be passed,
        //     this object can be set to null.
        //
        // Returns:
        //     true if this command can be executed; otherwise, false.
        bool CanExecute(object parameter);
       
//
        // Summary:
        //     Defines the method to be called when the command is invoked.
        //
        // Parameters:
        //   parameter:
        //     Data used by the command. If the command does not require data to be passed,
        //     this object can be set to null.
        void Execute(object parameter);
    }
}

Let's create a new ViewModel Class as shown below:
     
    public class ViewModel
    { 
        public ICommand PopupVM
        {
           
get
            {
                return new InvokeChildCommand();
            }
        } 
        public class InvokeChildCommand :
ICommand
        { 
            public bool CanExecute(object parameter)
            {
                if (parameter != null)
                {
                    CanExecuteChanged.Invoke(parameter, new EventArgs());
                }
                return true;
            }
 
            public event EventHandler CanExecuteChanged;
 
            public void Execute(object parameter)
            {
               
//Push the ViewModel into the Popup
                Child child = new Child();
                child.Show();
            }
        }
    }

Let's modify the XAML code of MainPage.xaml as shown below :

<UserControl x:Class="SLSimpleCommands.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">
 
    <Grid x:Name="LayoutRoot" Background="White">
        <Button Content="Open Child Window" Command="{Binding PopupVM}" Height="23" HorizontalAlignment="Left" Margin="128,92,0,0" Name="button1" VerticalAlignment="Top" Width="147" />      
   
</Grid>
</
UserControl>

Let's give it a run:

silverlight child window

Hit the Button. The child window will be opened.

This was a simple example where I created a simple command and bound it to the Silverlight Control.
 

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