how does the command pattern works?

Question

i am doing :

       <Button 
            Style="{StaticResource buttonstyle}"
            HorizontalAlignment="Left" Margin="12,21,10,0" 
            VerticalAlignment="Top" Height="78" Width="83" 
            BorderThickness="2" Content="add event"
            Command="{Binding NewEvent}" 
            CommandParameter="This is the report."
        >
        </Button>

where command is :

   public class StringDelegateCommand : ICommand 
{ 
    //methodes without return value
    Action<string> m_ExecuteTargets = delegate { };
    //methodes without parmtters inside
    Func<bool> m_CanExecuteTargets = delegate { return false; };
    //the value whom allows execution 
    bool m_Enabled = false;


    #region ICommand Members

    public bool CanExecute(object parameter)
    {
        Delegate[] targets = m_CanExecuteTargets.GetInvocationList();
        foreach (Func<bool> target in targets)
        {
            m_Enabled = false;
            bool localEnable = target.Invoke();
            if (localEnable)
            {
                m_Enabled = true;
                break;
            }
        }
        return m_Enabled;
    }

    public event EventHandler CanExecuteChanged = delegate { };

    public void Execute(object parameter)
    {
        if (m_Enabled)
            m_ExecuteTargets(parameter != null ? parameter.ToString() : null);
    }

    #endregion

    public event Action<string> ExecuteTargets
    {
        add
        {
            m_ExecuteTargets += value;
        }
        remove
        {
            m_ExecuteTargets -= value;
        }
    }

    public event Func<bool> CanExecuteTargets
    {
        add
        {
            m_CanExecuteTargets += value;
            CanExecuteChanged(this, EventArgs.Empty);
        }

        remove
        {
            m_CanExecuteTargets -= value;
            CanExecuteChanged(this, EventArgs.Empty);
        }
    }
}

and in my view model (which is binded in context so things do bind !!!):

 //called in ctor where newEvent is defined : StringDelegateCommand newEvent; 
     private void setNewEventCommand()
    {
        newEvent = new StringDelegateCommand();
        newEvent.CanExecuteTargets += isThereAnotherNewEvent;
        newEvent.ExecuteTargets += exacuteNewEvent;
        NewEvent = newEvent; 
    }

    void exacuteNewEvent(string message)
    {
        Window1 w = new Window1();
        w.ShowDialog();

    }

When I click on the button nothing happenes , what am I doing wrong ?can someone help me understand my error...

thank you ...

EDIT i should mention this is what the compliler writes :

System.Windows.Data Error: 40 : BindingExpression path error: 'NewEvent' property not found on 'object' ''viewModel' (HashCode=18612316)'. BindingExpression:Path=NewEvent; DataItem='viewModel' (HashCode=18612316); target element is 'Button' (Name=''); target property is 'Command' (type 'ICommand')

Answer 1

First of all, check if your binding binds at all. You can see binding errors in the Output window of Visual Studio at runtime. Or you can make somewhere a breakpoint, and look in the debugger what is the value of the button's Command (you would need to give a name to the button, in order to easily access it in the debugger: <Button x:Name="TEST" will allow to access TEST as a variable in your Window/Control).

Second, if the binding is correct, you should set a breakpoint in CanExecute and Execute and see what exactly happens.

Hope that helps.

Answer 2

问题得到了解决：该物业应已公开，然后一切正常。