Responding to context menu.

[Scottintexas]

I have a context menu in a view that calls the correct handler, but the command parameter is not being passed.

 <TextBlock DockPanel.Dock="Left"
                   Margin="0,3,1,0"
                   VerticalAlignment="Center">
            <TextBlock.ContextMenu>
                <ContextMenu>
                    <MenuItem Header="Associate USB"
                              Command="{Binding AssociateComportCommand}" />
                    <MenuItem Header= "TestPort"
                              Command="{Binding TestPortCommand}"
                              CommandParameter="{Binding ElementName=PortName, Path=Text}"/>
                    </ContextMenu>
            </TextBlock.ContextMenu>
            <Run Text="Com Port:"
                      Style="{StaticResource TitleStyle}"/>
            <Run  x:Name="PortName"
                      Text="{Binding Comport}"
                      Style="{StaticResource TitleStyle}"/>
            </TextBlock>

/// <summary>
        /// The event handler for the test port menu item
        /// </summary>
        public event EventHandler TestPort;

        /// <summary>
        /// Handles the Test Port command and fires the event so it can be
        /// picked up in the MainWindowViewModel.
        /// </summary>
        private void OnTestPort(string param)
        {
            var handler = TestPort;                                           //Break point here
            if (handler != null)
                handler(this, new ComPortEventArgs(param));
        }

        private RelayCommand testPortCommand;

        /// <summary>
        /// Allows the user to test the serial port.
        /// </summary>
        public ICommand TestPortCommand
        {
            get
            {
                if (testPortCommand == null)
                {
                    testPortCommand = new RelayCommand(param => OnTestPort((string)param));
                }
                return testPortCommand;
            }
        }

And finally the MainViewModel should subscribe to the event and call the proper method.

private void OnTestPort(object sender, ComPortEventArgs e)
        {
            ComPortViewModel cpvm = Ports.Where(x=> x.PortName == e.IDString).FirstOrDefault();
            cpvm.TestSerialPort();
        }

A breakpoint in the OnTestPort in the ViewModel with the context menu shows no value for the string param. So I am not getting it from the CommandParameter like I think I should. Also, this never makes it to the MainViewModel. I suppose it never makes it to the other view model because the parameter is missing. Maybe not. The thing is, I have done this before, but that was from a Button. And, yes, the value for the PortName is present.

Any ideas?

 

[Skydiver]

What happens if you just hard code a value for the the command parameter first in the XAML to make sure that it's not the binding that is causing the issue? Is that hardcoded value being passed in?

 

[Scottintexas]

Thanks, Skydiver,

Hard coding passed the parameter as expected, so I looked at the binding to the parameter. As soon as I try to bind to the text in the run where the port name is, I get null at the command. So it is the binding that is not right, but I don't see anything wrong with it. I am trying to find out if a binding to a run is allowed.