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Menu items disabled when setting a command

When I change this:

into this:

The MenuItem appears disabled. At first I thought it was the CommandBinding so I even wired up a CanExecute method but to no avail...

Does anybody know what's going on?

Thanks!

By the way IsEnabled="True" doesn't help either.

Erno de Weerd

Command= needs to have a Command object as its value, not an arbitrary string. There are system static classes like ApplicationCommands and others that have various commands as static fields. I think you want command="ApplicationCommands.New".

Michael (MVP C# / WPF)

MichaelLatta

Thanks for answering but unfortunately it's not the solution. I know that I can not assign *some* string. If I state *some* string I get a runtime error. So it must know New (and also accepts "ApplicationCommands.New")

Thanks

Erno de Weerd

A control which is attached to a command will be disabled if that command cannot be executed. Take the Application.Cut command for example. If the target of the command is a TextBox (which has built in support for the cut command) and there is no text selected, the control which executes the cut command will not be enabled, but if there is text selected the control is enabled.

You can see the same behavior in the edit context menu of Word, for example. If there is no text selected, the Cut context menuitem is disabled, but when there is text selected, the cut context menuitem is enabled.

Many controls have built in logic for some of the predefined commands, such as the TextBox control which supports copy, cut, paste, undo, redo. But other controls (or custom controls) may not have built in support so you??l have to add the command logic.

In your example you may just need to explicitly add a CommandTarget to the MenuItem. For example,

<MenuItem Command="ApplicationCommands.Copy"

CommandTarget="{Binding ElementName=TxtBox1}">

Defines the CommandTarget of the command to an instance of a TextBox control Named TxtBox1

If there is not a CommandTarget defined, the control with focus will be set to the CommandTarget.

Probably though there is not an Executed or a CanExecute method bound to the command. The CanExecute method returns false if the command can not be executed, which in turn disables the control. Try wiring up an Executed method and an CanExecute method in the CommandBinding. Next you??l want to create the Executed and CanExecute methods in code behind.

XAML Code: (you can place this CommandBinding on the Menu itself or grandparent of the menuitem, but I like to put all the CommandBindings I can on the main Window element. RoutedCommands act like input events and bubble or tunnel up the UI tree, so as long as the binding is a parent, it will be executed. Keep in mind though, if there are multiple bindings for the command only the first one hit will be applied)

<Window.CommandBindings>

</Window.CommandBindings>

. . .

In Code Behind

public void NewExecute(object sender, ExecutedRoutedEventArgs e)

{

// place Command execute logic here

}

public void OnQuery(object sender, CanExecuteRoutedEventArgs e)

{

// place whatever logic you want to insure that the execute is valid for your scenario

e.CanExecute = true;

}

I hope this helps.

Brian

Brian Love [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

Brian Love

I left out the part of the CommandBinding

<Window.CommandBindings>

</Window.CommandBindings>

Brian Love [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

Brian Love

Hmmm... ok this works. But I'm am curious why my code didn't work because I did the same thing but from within code:

        public MainWindow()
        {
            InitializeComponent();

            CommandBinding cmd;
            cmd = new CommandBinding(ApplicationCommands.New, new ExecutedRoutedEventHandler(CommandNew_Executed), new CanExecuteRoutedEventHandler(Command_CanExecute));
        }

Is this the wrong place/moment to do this?

Thanks!

Erno de Weerd

That code looks correct. All you need to do now is add the CommandBinding to the UIElement you want it attached to. RoutedCommands are essentially input events and are routed up and down the UI tree, so the CommandBinding needs to be associated with a UIElement in order for it to be applied.

If you are defining the main window in XAML, you can give it a name and then reference that name in the code behind.

XAML:

<Window . . .

Name="MyWIndow">

</Window>

Code Behind:

       public MainWindow()
        {
            InitializeComponent();

            CommandBinding cmd;
            cmd = new CommandBinding(ApplicationCommands.New, new ExecutedRoutedEventHandler(CommandNew_Executed), new CanExecuteRoutedEventHandler(Command_CanExecute));

MyWindow.CommandBindings.Add(cmd);

}

Brian Love [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

Brian Love

Arg! That's it! I forgot the MyWindow.CommandBindings.Add(cmd);

Thank you so much!

BTW: instead of MyWindow I simply use this

Erno de Weerd

I had this same problem but I had the CommandBindings hooked up correctly it was just that I had to e

Corbin Hoenes

Anybody knows what's the expected behavior when press key combination: "Ctrl+N"?

If I add event handler, "NewClicked", Ctrl+N won't find the event, anybody know why?