MVVM and Commanding

[Mike Kacos]

Hi,
   I'm trying to find out if I can do what I'm hoping to do.  I've been looking at your demo for commanding,(http://demos.telerik.com/silverlight/#GridView/Commands), but I'm trying to do something a little different.  When I hit the Save Insert/Edit button (from the example) I want to fire off custom code in my ViewModel.  Now I like the behavior of the button in the example where they are enabled and disabled based on whether or not the user has begun editing etc... but I don't know how to then make my code fire.  

My example would be if I have a grid whose ItemSource is a collection of objects or type CARS.  I have a SelectedItem of type Car called SelectedCar.  I have a  SaveCommand in my ViewModel that performs an update on a SINGLE Car object.  IS there a way to achieve the desired results of enabling and disabling the button based on the Grid mode (i.e. editing) but then fire a command from my viewmodel?

Thanks in advance,

-Mike

[Ivan Ivanov]

Hi Mike Kacos,

You may try using a custom button type that not only executes the command, but adds your custom code.

public class CustomButton : RadButton
    {
        public CustomButton()
        {
            Click += (sender, e) =>
            {
                if (Command == RadGridViewCommands.Delete &&
RadGridViewCommands.Delete.CanExecute(null))

                {
                    RadGridViewCommands.Delete.Execute(null);
                            // Your Code comes here.
                }
            };
        }

        public static DependencyProperty CommandProperty =
            DependencyProperty.Register("Command",
                                        typeof(ICommand), typeof(CustomButton),
                                        new PropertyMetadata(null));

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

Regards,
Ivan Ivanov
the Telerik team

[Mike Kacos]

Thanks for the Reply.  I tried implementing this however, it does not seem to give me the functionality I want.  The button stays enabled no matter what.  The button I'm trying to implement is a "Save Insert/Edit" (Not Delete), but the button remains enabled the entire time.  I am looking to get the button to become enabled ONLY when the user clicks into a cell to begin editing and disabled once the user is finished editing.

-Mike

[Ivan Ivanov]

Hi Mike Kacos,

Well, I have given you an example utilizing a random command. To be more specific to your case, I have prepared a sample project for you, which implements the same functionality of the "Save" button as in the demo. Please, refer to it and inform us if this solution fits into your requirements.


All the best,
Ivan Ivanov
the Telerik team

[Mike Kacos]

Thanks for taking the time to create the sample project for me.  Unfortunately the project doesn't seem to be working as I'd expect.  The enabling/disabling of the button works great, however the custom code (Specifically the "

 MessageBox.Show( "this value has been updated" );") never fires.  

[Ivan Ivanov]

Hello Mike Kacos,

Well, in order to trigger the "custom code", you should press the button and invoke the command. Please, refer to this clip and let us know, if you could replicate the desired behavior:
Command button example


All the best,
Ivan Ivanov
the Telerik team

[Mike Kacos]

Thanks, I see that it does work from the clip, however it's not working for me locally from the project you sent.  I'll try to dig in a bit more and see if I can figure out what's going on.  Thanks.

[Ivan Ivanov]

Hi Mike Kacos,

It is quite strange that you cannot replicate this. Could you please put a breakpoint in the event handler's block, in order to check if everything carries out correctly? 

Greetings,
Ivan Ivanov
the Telerik team