ICommand with MVVM in WPF

Question

I am new to MVVM and WPF, trying to use ICommand in WPF and MVVM. Below is the code.

Can someone please help to know why the below code is not working, means nothing happens on button click.

Appreciate your help.

View

<Grid>
    <Button  Height="40" Width="200" Name="button1" Command="{Binding Path=Click}">Click Me</Button>
</Grid>

App.xaml.cs

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
        MainWindow mainWindow = new MainWindow();
        MainWindowViewModel vm = new MainWindowViewModel();
        mainWindow.DataContext = vm;
    }            
}

MainWindowViewModel.cs

namespace TestWPFApplication.ViewModel
{
    public class MainWindowViewModel 
    {
        private ICommand _click;

        public ICommand Click
        {
            get
            {
                if (_click == null)
                {
                    _click = new CommandTest();
                }
                return _click;
            }
            set 
            {
                _click = value;
            }
        }

        private class CommandTest : ICommand
        {
            public bool CanExecute(object parameter)
            {
                return true;
            }

            public event EventHandler CanExecuteChanged;

            public void Execute(object parameter)
            {
                MessageBox.Show("Hi! Test");
            }    
        }
    }            
}

default.kramer default.kramer · Accepted Answer · 2013-09-26T13:45:48

It looks like your OnStartup method is instantiating a MainWindow and never showing it. You probably have the StartupUri set in XAML which is creating a different MainWindow with the data context not set.

You could remove the StartupUri and call mainWindow.Show(). Alternatively, you could get rid of the OnStartup method and set up the data context in the main window's constructor.

ICommand with MVVM in WPF

2 Answers