Add CommandParameter to Button

[Daniel-Svensson]

The current draft includes support for the Command property on button, I would like to also se the CommandParamter property.

Why

• CommandParameter is required to fulle use the Command property which is already part of the draft.
• The methods of the ICommand interface all takes an parameter of type object. The object itself is taken from the CommandParamter property of the button for all the large XAML runtimes so it
• Adds much value for MVVM scenarios

Availability UWP, Xamarin, WPF, Silverlight

Examples `

or

`

[monkeynoises]

Provide the ability to support multiple parameters. Here's a proposal:

CommandParameters="{Binding SelectedXXX}{Binding OtherProperty}{x:Int 1}{x:String foo}"

The ICommandSource interface would look something like this:

   interface ICommandSource
    {
        ICommand Command { get; }

        object CommandParameter { get; }

        object []CommandParameters { get; }

        IInputElement CommandTarget { get; }

        object this[int index]
        {
            get;
            set;
        }
    }

CommandParameter would just be an alias for accessing the first parameter in code behind (so as not to break existing code).....(or just deprecate CommandParameter entirely, and make CommandParameters the default for single and multiple parameters).

The indexer just makes it a bit more natural to access the parameters through the interface.

Literals could be specified by using the "type".

Element syntax would be:

<Thing.CommandParameters>
<Binding Path="SelectedXXX"/>
<Binding Path="OtherProperty"/>
<x:Int>1</x:Int>
<x:String>foo</x:String>
</Thing.CommandParameters>

[Odonno]

It is sure we should add CommandParameter as it is already implemented in WPF, UWP or even Xamarin.

I am also interested by the proposal of @monkeynoises, I think the Command pattern of MVVM should be more flexible by allowing multiple parameters for example.

[swythan]

If you could get the WPF team to fix their Button implementation to re-evaluate the Command's CanExecute when the CommanParameter changes, that would also be helpful. That was logged (in Connect) as bug in WPF years ago.