How do I get the height and width from a DockPanel?

Question

I am using a DockPanel to host some image enhancement controls. The image to be enhanced is in the 'center' dock position. I would like to have the image fill the entire area of the DockPanel. I have a custom class that implements the WPF Canvas control and takes a windows.Rect as input. This Rect will set the area for the image render function which I have overridden.

I have tried to get the DockPanel.ActualHeight and .ActualWidth. both are NaN and the DockPanel.Width and Height = 0.

    public MainWindow()
    {
        ImageDataModel = new ImageDataModel();
        DataContext = ImageDataModel;
        InitializeComponent();
        WindowState = WindowState.Maximized;
        var tmpWindow = Window.GetWindow(BaseDockPanel);
        Rect rect = new Rect(0, 0, BaseDockPanel.ActualWidth, BaseDockPanel.ActualHeight);
        bitmapCanvas = new BitMapCanvas(rect);
        BaseDockPanel.Children.Add(bitmapCanvas);
    }

I would like to be able to create a windows.Rect that is the actual dimension of the DockPanel.center height and width. Currently the height and width for the control are 0.

Answer 1

At the point of the construction of MainWindow, the child controls within the Window, in your case BaseDockPanel has not been loaded yet.

That is why you're getting a 0 for it's ActualWidth and ActualHeight.

What you can do is add an EventHandler for the Window's Loaded event as shown below.

public MainWindow()
{
    ImageDataModel = new ImageDataModel();
    DataContext = ImageDataModel;
    InitializeComponent();
    WindowState = WindowState.Maximized;

    this.Loaded += Window_Loaded;
}

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    var tmpWindow = Window.GetWindow(BaseDockPanel);
    // You will get your ActualWidth and ActualHeight here.
    Rect rect = new Rect(0, 0, BaseDockPanel.ActualWidth, BaseDockPanel.ActualHeight);
    bitmapCanvas = new BitMapCanvas(rect);
    BaseDockPanel.Children.Add(bitmapCanvas);
}