CODEWITHSUNDEEP
c#wpfmvvm
Apoorv
Apoorv

Reputation: 2043

Unable to override in MVVM

I have a peculiar problem where I have to override a particular method present in the Window class .

I am using MVVM and my ViewModel is inheriting to BaseVm which has INotifyPropertyChanged

What I need is this 

    public partial class MainWindow : Window
     {
 protected override void OnSourceInitialized(EventArgs e)
        {
                base.OnSourceInitialized(e);

                // Hook up handler for window messages
                var windowSource = PresentationSource.FromVisual(this) as HwndSource;
                if (windowSource == null)
                    return;
                windowSource.AddHook(WiDiOnWindowMessage);

                try
                {
                    _wiDi = new WiDi();
                    _wiDi.ValidateWiDi();

                    //// This is async call so rest of logic handled in OnWiDiWindowMessage
                    //// Pass the window handle which WiDi extensions library uses to send messages back.
                    _wiDi.Initialize((uint)windowSource.Handle.ToInt64());
                }
                catch (WiDiNoWelException)
                {
                    ShowMessageDialog("Warning: The Intel® WiDi auto-connect button is not available.",
                                      "Please use the Intel® WiDi application to connect to your TV.\n" +
                                      "Alternatively you can use an HDMI cable.\n" +
                                      "Issue: The Intel® WiDi Extensions Library (WEL) cannot be found.");
                }
                catch (WiDiNoAppException)
                {
                    ShowMessageDialog("Warning: Intel® WiDi is not available.", 
                                      "Please use an HDMI cable to connect to your TV.\n" +
                                      "Issue: Intel® WiDi cannot be found or this PC may not be Intel® WiDi compatible.");
                }
                catch (WiDiException exception)
                {
                    ShowMessageDialog("Warning: Intel® WiDi is not available.",
                                      "Please use an HDMI cable to connect to your TV.\n" +
                                      "Issue: " + exception.Message);
                }

My Current code is

public  class HomeWindowVm : BaseVm
    {
     protected override void OnSourceInitialized(EventArgs e)
       {
            base.OnSourceInitialized(e);

        //    Hook up handler for window messages

         var windowSource = PresentationSource.FromVisual(this) as HwndSource;
           // var windowsource = PresentationSource.FromVisual(this) as HwndSource;
        if (windowSource == null)
             return;
         windowSource.AddHook(WiDiOnWindowMessage);

         try
          {
               _wiDi = new WiDi();
              _wiDi.ValidateWiDi();

                // This is async call so rest of logic handled in OnWiDiWindowMessage
                // Pass the window handle which WiDi extensions library uses to send messages back.
                _wiDi.Initialize((uint)windowSource.Handle.ToInt64());
            }
            catch (WiDiNoWelException)
            {
                ShowMessageDialog("Warning: The Intel® WiDi auto-connect button is not available.",
                                  "Please use the Intel® WiDi application to connect to your TV.\n" +
                                  "Alternatively you can use an HDMI cable.\n" +
                                  "Issue: The Intel® WiDi Extensions Library (WEL) cannot be found.");
            }
            catch (WiDiNoAppException)
            {
                ShowMessageDialog("Warning: Intel® WiDi is not available.",
                                  "Please use an HDMI cable to connect to your TV.\n" +
                                  "Issue: Intel® WiDi cannot be found or this PC may not be Intel® WiDi compatible.");
            }
            catch (WiDiException exception)
            {
                ShowMessageDialog("Warning: Intel® WiDi is not available.",
                                  "Please use an HDMI cable to connect to your TV.\n" +
                                  "Issue: " + exception.Message);
            }
        }

My problem is that as my Class in Not inheriting fro Window .the OnSourceInitialized(EventArgs e) is giving errors > .

how can I inherit from Window Class in the same code.

Upvotes: 1

Views: 576

Answers (2)

Clemens
Clemens

Reputation: 128097

Your view model could probably have a SourceInitialized method that you attach to the Window's SourceInitialized event (instead of overriding the OnSourceInitialized method):

public class HomeWindowVm : BaseVm
{
    public void SourceInitialized(object sender, EventArgs e)
    {
        var window = (Window)sender;
        var windowSource = PresentationSource.FromVisual(window) as HwndSource;
        ...
    }
}

When you create your view model instance, you would attach the handler like this:

public MainWindow()
{
    InitializeComponent();

    var vm = new HomeWindowVm();
    SourceInitialized += vm.SourceInitialized;
    DataContext = vm;
}

Upvotes: 2

Nitin Purohit
Nitin Purohit

Reputation: 18578

You cannot do this in your ViewModel as you can see that OnSourceInitialized is a Window function and hence can only be overridden in the derived Window class. It does not make sense to derive VM from Window as VM is intended to provide DataContext to the View (window in your case). Even if you derive VM from Window it would not be the Window that you want to override this function.

So in this case you can either keep this code in your Windows code behind which I don't think is a voilation to MVVM here.

OR you can define a attached behavior and put it on your Window class and check everything in the behavior itself.

Upvotes: 0

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