Question

I’m developing my first WPF app for university using MVVM. I cannot get this specific binding to work, although i’ve followed the steps used previously that have been successful.

I have the following xaml snippet:

    <Button Command="{Binding GetTicketsCommand}" Canvas.Left="50" Canvas.Top="202"    Content="Refresh List" Height="25" Width="137" />

The view initialises the VM as such:

public JobListView()
    {
        InitializeComponent();
        viewModel = new JobListViewModel(this);
        this.DataContext = viewModel;
    }

The viewmodel has the command called GetTicketsCommand which the button binds to, but when I click the button the command Execute or CanExecute methods do not get called. The command that I created is getting instantiated in the VM constructor.

Any ideas?

Edit:

The command class is like this:

public class GetTicketsCommand  : ICommand
{
    private readonly JobListViewModel viewModel;

    public GetTicketsCommand(JobListViewModel viewModel)
    {
        this.viewModel = viewModel;     
    }

    public bool CanExecute(object parameter)
    {
        return true;
    }

    public void Execute(object parameter)
    {
        viewModel.GetTickets();
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }
}

And in the viewmodel I simply create an instance of it in the constructor:

public JobListViewModel()
    {
        GetTicketsCommand = new GetTicketsCommand(this);
        dataAccess = new DataLayerClient();
    }

Answer 1

Bindings only work with properties. Make sure that your GetTicketsCommand command within your view model is a property:

public ICommand GetTicketsCommand { get; set; }

rather than a field:

public ICommand GetTicketsCommand;