RadColorPicker and EventToCommand

[Charles Bates]

Hello,
We are using the GalaSoft MVVM Light toolkit, and would like to use EventToCommand with the RadColorPicker, like this:

<RadColorPicker>
<!-- stuff -->
<i:Interaction.Triggers>

    <i:EventTrigger EventName="Click">

        <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding ChangeLinkColorCommand}" PassEventArgsToCommand="True"/>

    </i:EventTrigger>

    <i:EventTrigger EventName="SelectedColorChanged">

        <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding ChangeLinkColorCommand}" PassEventArgsToCommand="True"/>

    </i:EventTrigger>

</i:Interaction.Triggers>
</RadColorPicker>

The Click and SelectionColorChanged handlers receive System.EventArgs, which don't appear to have much information.
Can we use EventToCommand with these events on the RadColorPicker?  How do we find the sender, and things like the SelectedColor property?

Thanks for any tips....

[Petar Mladenov]

Hi Charles Bates,

The newly selected color should be accessed in the SelectedColorChanged event handler like so:

Color selColor = (sender as RadColorPicker).SelectedColor as Color;

Let us know if you need further assistance on this.



Greetings,
Petar Mladenov
the Telerik team

[kamlnedra]

i too want to know how to get the "sender" in this case. please reply @ earliest.if i will get i will definitely post it.
[e-mail]

thanks, in advance!

[Petar Mladenov]

Hello kamlnedra,

Unfortunately, you cannot use the SelectedColorChanged and EventToCommand because the EventArgs does not provide info for the sender (in this case you cannot use e.Source or e.OriginalSource). On the other hand, in a typical MVVM scenario , the ViewModel should not know the sender of the events/commands, this is considered bad practice. Let us know if you have further questions.

Best wishes,
Petar Mladenov
the Telerik team

[Michael]

I love your controls, but that's a really lame answer which speaks to poor design of this otherwise awesome control.  I just ran into this problem, so I threw together a quick behavior that solves this problem.  You'll of course need the Blend SDK (or Prism) so you can include a reference to System.Windows.Interactivity.

Usage:

<telerik:RadColorPicker>
    <i:Interaction.Behaviors>
        <local:ForwardColorToCommand Command="{Binding MyCommand}"/>
    </i:Interaction.Behaviors>
</telerik:RadColorPicker>

Code:

using System.Windows;
using System.Windows.Input;
using System.Windows.Interactivity;
using Telerik.Windows.Controls;

namespace Ows.Modules.HelloWorld
{
    public class ForwardColorToCommand : Behavior<RadColorPicker>
    {
        public static readonly DependencyProperty CommandProperty =
            DependencyProperty.Register("Command", typeof (ICommand), typeof (ForwardColorToCommand), new PropertyMetadata(null, (s, e) => { }));

        public ICommand Command
        {
            get { return (ICommand) GetValue(CommandProperty); }
            set { SetValue(CommandProperty, value); }
        }

        protected override void OnAttached()
        {
            base.OnAttached();

            AssociatedObject.SelectedColorChanged += OnColorChanged;
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            AssociatedObject.SelectedColorChanged -= OnColorChanged;
        }

        private void OnColorChanged(object sender, System.EventArgs e)
        {
            var picker = sender as RadColorPicker;
            if (picker == null)
                return;

            var command = Command;
            if (command == null)
                return;

            var newColor = picker.SelectedColor;
            if (command.CanExecute(newColor))
                command.Execute(newColor);
        }
    }
}