Question

i need to invoke multiple instances of a command

for this example i’ll take 2 controls ‘A’ and ‘B’

‘A’ would be the Invoker and ‘B’ the invokie and there are multiple instances of ‘B’

the Controls :

 public class A : Control 
 {
     public A()
     {}

     public ICommand OnACommand   
     {
        get { return (ICommand)GetValue(OnAProperty); }
        set { SetValue(OnACommandProperty, value); }
     }

    public static readonly DependencyProperty OnACommandProperty =
        DependencyProperty.Register("OnACommand", typeof(ICommand), typeof(A), new UIPropertyMetadata(null));

     public bool Something   
     {
        get { return (bool)GetValue(SomethingProperty); }
        set { SetValue(SomethingProperty, value); }
     }

    public static readonly DependencyProperty SomethingProperty=
        DependencyProperty.Register("Something", typeof(bool), typeof(A), new UIPropertyMetadata(false,OnSometingPropertyChanged));

    private static void  OnSometingPropertyChanged(...)
    {
        ... 
        OnACommand.Execute(this.Value);
    }                  
 }


 public class B : Control 
 {
     public B(){ }

     public ICommand OnBCommand   
     {
        get { return (ICommand)GetValue(OnBCommandProperty); }
        set { SetValue(OnBCommandProperty, value); }
     }

    public static readonly DependencyProperty OnBCommandProperty =
        DependencyProperty.Register("OnBCommand", typeof(ICommand), typeof(B), new UIPropertyMetadata(null));              
 }

the Binding :

   <local:B  x:Name="B1" OnBCommand="{Binding ElementName=A1 , Path=OnACommand />
   <local:B  x:Name="B2" OnBCommand="{Binding ElementName=A1 , Path=OnACommand />   
   <local:A  x:Name="A1"  />   

what i need is for all the B Commands Bound to that A command to Execute when Executing OnACommand.

the only approach which i would think to work is if i implemented the Command inside B and bound it OneWayTosource , but than only the last one the Bind to A would be the B which would get Executed .

  public B()
  {
       OnBCommand = new RelayCommand<int> 
                    (
                        value => { this.Value = value ....}
                    );
  }

   <local:B  x:Name="B1" 
             OnBCommand="{Binding ElementName=A1,Path=OnACommand,Mode=OneWayToSource />
   <local:B  x:Name="B2" 
             OnBCommand="{Binding ElementName=A1,Path=OnACommand,Mode=OneWayToSource />   
   <local:A  x:Name="A1"  />   

if i bound it any other way like OneWay i need to implement the Command in A and B has no idea
that it was even executed, unless it’s possible to some how acknowledge the execution from a delegate within B ..

so to summarize i need to execute multiple targets from one source.

in addition i might point out that i solved this using a regular .net event which i declared in ‘A1’
and Subscribed all the B’s to,but since this is WPF written in MVVM i’m looking for the MVVM Style Way of doing this , using Commands .

thanks in advance.

Answer 1

A possible approach to achieve what you are trying to get done is using a composite command.