如何更改自定义控件 IsMouseOver 的属性值

Question

• i create custom frameworkelement ( notifyicon ).

• i listening windows message callback.

• i want Onmouseenter changed ismouseover,but ismouseover is RegisterReadOnly.

• i cannot changed

   private IntPtr CallBack(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam) { if (IsLoaded) { var wm = lparam.ToInt32(); switch (wm) { case WM.LBUTTONDBLCLK: OnMouseDoubleClick(); break; case WM.LBUTTONDOWN: OnMouseDown(MouseButton.Left); break; case WM.LBUTTONUP: OnMouseUp(MouseButton.Left); break; case WM.RBUTTONDOWN: OnMouseDown(MouseButton.Right); break; case WM.RBUTTONUP: OnMouseUp(MouseButton.Right); break; case WM.MOUSEMOVE: OnMouseEnter(); OnMouseMove(); break; } } return User32.DefWindowProc(hwnd, msg, wparam, lparam); } private void OnMouseEnter() { IsMouseOver = true;// cannot changed }

Answer 1

You don't. As the docs states, you shouldn't really do this:

Some of the dependency properties defined in the WPF framework are read-only. The typical reason for specifying a read-only dependency property is that these are properties that should be used for state determination, but where that state is influenced by a multitude of factors, but just setting the property to that state isn't desirable from a user interface design perspective. For example, the property IsMouseOver is really just surfacing state as determined from the mouse input. Any attempt to set this value programmatically by circumventing the true mouse input would be unpredictable and would cause inconsistency.

You can set the dependency property using reflection:

DependencyPropertyKey key = (DependencyPropertyKey)typeof(UIElement).GetField("IsMouseOverPropertyKey",
               BindingFlags.NonPublic | BindingFlags.Static).GetValue(this);

SetValue(key, true);

This will however not affect the IsMouseOver CLR property which gets its value from an internal flag field rather than from the dependency property:

public bool IsMouseOver
{
    get
    {
        return ReadFlag(CoreFlags.IsMouseOverCache);
    }
}

So if want to customize the way to detect whether the mouse is over your control, you'd better create your own property that you can set however you want.