Make WPF window draggable, no matter what element is clicked

Question

My question is 2 fold, and I am hoping there are easier solutions to both provided by WPF rather than the standard solutions from WinForms (which Christophe

Answer 1

Sometimes, we do not have access to Window, e.g. if we are using DevExpress, all that is available is a UIElement.

Step 1: Add attached property

The solution is to:

1. Hook into MouseMove events;
2. Search up the visual tree until we find the first parent Window;
3. Call .DragMove() on our newly discovered Window.

Code:

using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace DXApplication1.AttachedProperty
{
    public class EnableDragHelper
    {
        public static readonly DependencyProperty EnableDragProperty = DependencyProperty.RegisterAttached(
            "EnableDrag",
            typeof (bool),
            typeof (EnableDragHelper),
            new PropertyMetadata(default(bool), OnLoaded));

        private static void OnLoaded(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            var uiElement = dependencyObject as UIElement;
            if (uiElement == null || (dependencyPropertyChangedEventArgs.NewValue is bool) == false)
            {
                return;
            }
            if ((bool)dependencyPropertyChangedEventArgs.NewValue  == true)
            {
                uiElement.MouseMove += UIElementOnMouseMove;
            }
            else
            {
                uiElement.MouseMove -= UIElementOnMouseMove;
            }

        }

        private static void UIElementOnMouseMove(object sender, MouseEventArgs mouseEventArgs)
        {
            var uiElement = sender as UIElement;
            if (uiElement != null)
            {
                if (mouseEventArgs.LeftButton == MouseButtonState.Pressed)
                {
                    DependencyObject parent = uiElement;
                    int avoidInfiniteLoop = 0;
                    // Search up the visual tree to find the first parent window.
                    while ((parent is Window) == false)
                    {
                        parent = VisualTreeHelper.GetParent(parent);
                        avoidInfiniteLoop++;
                        if (avoidInfiniteLoop == 1000)
                        {
                            // Something is wrong - we could not find the parent window.
                            return;
                        }
                    }
                    var window = parent as Window;
                    window.DragMove();
                }
            }
        }

        public static void SetEnableDrag(DependencyObject element, bool value)
        {
            element.SetValue(EnableDragProperty, value);
        }

        public static bool GetEnableDrag(DependencyObject element)
        {
            return (bool)element.GetValue(EnableDragProperty);
        }
    }
}

Step 2: Add Attached Property to any element to let it drag the window

The user can drag the entire window by clicking on a specific element, if we add this attached property:

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Appendix A: Optional Advanced Example

In this example from DevExpress, we replace the title bar of a docking window with our own grey rectangle, then ensure that if the user clicks and drags said grey rectagle, the window will drag normally:

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Disclaimer: I am not affiliated with DevExpress. This technique will work with any user element, including standard WPF or Telerik (another fine WPF library provider).