How to create bindable commands in Custom control?

24
votes

Assuming a code like below,

public class SomeViewModel{
      ICommand ReloadCommand{get...}
      ICommand SaveCommand{get..}
}

//SomeView.xaml
<SomeCustomControl Reload="ReloadCommand" Save="SaveCommand" /> //NOT SURE HOW??

//SomeCustomContro.xaml
<SomeCustomControl x:Name="someCustomControl">
<Button Command={Binding ElementName=someCustomControl, Path=Reload />
<Button Command={Binding ElementName=someCustomControl, Path=Save />
</SomeCustomControl>

//SomeCustomControl.xaml.cs
.....  //NOT SURE HOW TO ALLOW BINDING TO A ICOMMAND ??

In my SomeCustomControl, I need to support "binding of ICommand in xaml". I understand DependencyProperties could be bind like this, but in this case I need to bind ICommand.

Can somebody please suggest what is the best way to do this? Any suggested material or link would be of use because I am missing a direction.

EDIT 1) I can use the DataContext SomeView in SomeCustomControl. There is more logic and separation between the two which I can not dissolve. I 'must' maintain a reference of Reload/Save ICommands somewhere in my SomeCustomControl.

Thanks a lot.

2
wpfxamlbinding

2 Answers

44
votes

Let me get you straight, you want to bind to the Reload and Save right?

So that needs creating, declaring and defining two dependency properties ReloadCommandProperty and SaveCommandProperty of type ICommand for SomeCustomControl.

So assuming that SomeCustomControl derives from Control ...

public class SomeCustomControl : Control
{
    public static DependencyProperty ReloadCommandProperty
        = DependencyProperty.Register(
            "ReloadCommand",
            typeof (ICommand),
            typeof (SomeCustomControl));

    public static DependencyProperty SaveCommandProperty
        = DependencyProperty.Register(
            "SaveCommand",
            typeof(ICommand),
            typeof(SomeCustomControl));

    public ICommand ReloadCommand
    {
        get
        {
            return (ICommand)GetValue(ReloadCommandProperty);
        }

        set
        {
            SetValue(ReloadCommandProperty, value);
        }
    }

    public ICommand SaveCommand
    {
        get
        {
            return (ICommand)GetValue(SaveCommandProperty);
        }

        set
        {
            SetValue(SaveCommandProperty, value);
        }
    }
}

After this proper binding to RelodCommand and SaveCommand properties will start working...

     <SomeCustomControl RelodCommand="{Binding ViewModelReloadCommand}"
                        SaveCommand="{Binding ViewModelSaveCommand}" />
3
votes

Create a property that will return your command and bind this property wherever needed.

private ICommand _reloadCommand;
public ICommand ReloadCommand
{
  get 
  { 
    if(_reloadCommand == null) _reloadCommand = CreateReloadCommand();
    return _reloadCommand;
  }
}

Change the binding in your code to

<Button Command={Binding ReloadCommand}" />

And bind the custom control DataContext to the view model that contains the commands.