c# - How do you disable Aero Snap in an application?

Question

Is it possible to disable the automatic window-docking feature of Windows 7 in a WPF application?

Answer 1

I recently needed to do this to a custom, resizable ResizeMode = CanResizeWithGrip WPF window with no window decorations (no title bar and buttons). I used DragMove() to move the window, and when It is maximized by AeroSnap, the window becomes unmovable and hence locked in place.

I tried Barn Monkey's solution, which partially worked, but it would still show the AeroSnap graphic and resize the app to fullscreen size. I modified it below and now it works as expect: still resizable, but no AeroSnap at all.

void Window1_MouseDown(object sender, MouseButtonEventArgs e)
{
    if( e.LeftButton == MouseButtonState.Pressed )
    {
        // this prevents win7 aerosnap
        if( this.ResizeMode != System.Windows.ResizeMode.NoResize )
        {
            this.ResizeMode = System.Windows.ResizeMode.NoResize;
            this.UpdateLayout();
        }

        DragMove();
    }
}

void Window1_MouseUp( object sender, MouseButtonEventArgs e )
{
    if( this.ResizeMode == System.Windows.ResizeMode.NoResize )
    {
        // restore resize grips
        this.ResizeMode = System.Windows.ResizeMode.CanResizeWithGrip;
        this.UpdateLayout();
    }
}

EDIT:

It's been a while since I wrote this, but since people still look at this I'll update it with what I use now. I still use basically the same method for preventing edge snapping and moving my windows, but I now have them packed into custom Behavior<> classes that I can attach to a Window or UserControl. This makes them very easy to use with MVVM (I use Caliburn Micro).

The behavior classes are:

/// <summary>
/// behavior that makes a window/dialog draggable by clicking anywhere 
/// on it that is not a control (ie, button)
/// </summary>
public class DragMoveBehavior<T> : Behavior<T> where T : FrameworkElement
{
    protected override void OnAttached()
    {
        AssociatedObject.MouseLeftButtonDown += MouseDown;
        base.OnAttached();
    }

    protected override void OnDetaching()
    {
        AssociatedObject.MouseLeftButtonDown -= MouseDown;
        base.OnDetaching();
    }

    void MouseDown( object sender, EventArgs ea ) => Window.GetWindow( sender as T )?.DragMove();
}

public class WinDragMoveBehavior : DragMoveBehavior<Window> { }

public class UCDragMoveBehavior : DragMoveBehavior<UserControl> { }

/// <summary>
/// behavior that makes a window/dialog not resizable while clicked.  this prevents
/// the window from being snapped to the edge of the screen (AeroSnap).  if DragMoveBehavior
/// is also used, this must be attached first.
/// </summary>
/// <typeparam name="T"></typeparam>
public class NoSnapBehavior<T> : Behavior<T> where T : FrameworkElement
{
    ResizeMode lastMode = ResizeMode.NoResize;
    protected override void OnAttached()
    {
        AssociatedObject.MouseLeftButtonDown += MouseDown;
        AssociatedObject.MouseLeftButtonUp += MouseUp;
        base.OnAttached();
    }

    protected override void OnDetaching()
    {
        AssociatedObject.MouseLeftButtonDown -= MouseDown;
        AssociatedObject.MouseLeftButtonUp -= MouseUp;
        base.OnDetaching();
    }

    /// <summary>
    /// make it so the window can be moved by dragging
    /// </summary>
    void MouseDown( object sender, EventArgs ea )
    {
        var win = Window.GetWindow( sender as T );
        if( win != null && win.ResizeMode != ResizeMode.NoResize )
        {
            lastMode = win.ResizeMode;
            win.ResizeMode = ResizeMode.NoResize;
            win.UpdateLayout();
        }
    }

    void MouseUp( object sender, EventArgs ea )
    {
        var win = Window.GetWindow( sender as T );
        if( win != null && win.ResizeMode != lastMode )
        {
            win.ResizeMode = lastMode;
            win.UpdateLayout();
        }
    }
}

public class WinNoSnapBehavior : NoSnapBehavior<Window> { }

public class UCNoSnapBehavior : NoSnapBehavior<UserControl> { }

I then attach them to my dialog box Views with:

<UserControl ...
  xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
  xmlns:util:="...">
  <i:Interaction.Behaviors>
    <util:UCNoSnapBehavior/>
    <util:UCDragMoveBehavior/>
  </i:Interaction.Behaviors>

  ...

</UserControl>

And it just works!