在winforms中，如何使控件不接受鼠标事件

Question

I have a button and upon mouseenter, a little form pops up, and upon mouseleave of the button, the little form disappears. I am needing this form to not accept any mouse events, in other words, be "invisible" to the mouse.

The problem is, the form pops up under the mouse, which triggers the mouseleave event for the button. I know there are other ways to get around this, but i'm needing the form to hide when the mouse leaves the original button that triggered the form, and I also need the form to appear underneath the mouse.

So how can I make the little pop-up form invisible to mouse-events, so that it doesn't cause the "mouse leave" event to trigger for the button?

The popup is of type "Form". Here is the mouseEnter and mouseLeave code that triggers showing and hiding the form:

private void btnPatientSearch_MouseEnter(object sender, EventArgs e)
        {
                _currentPatientInfo = new PatientInfo()
                {
                    MdiParent = this.MdiParent
                };
                _currentPatientInfo.Show();
                _currentPatientInfo.Location = new Point(181, 9);
            }
        }

        private void btnPatientSearch_MouseLeave(object sender, EventArgs e)
        {
            if (_currentPatientInfo == null) return;
            _currentPatientInfo.Hide();
            _currentPatientInfo = null;
        }

Answer 1

Inherit your popup form from the following form class. This code is using some p/invokes and not tested, but it should work.

public class PopupForm : Form
{
  private const int WS_BORDER = 0x00800000;
  private const int WS_POPUP = unchecked((int)0x80000000);

  private const int WS_EX_TOPMOST = 0x00000008;
  private const int WS_EX_NOACTIVATE = 0x08000000;

  private const int WM_MOUSEACTIVATE = 0x0021;
  private const int MA_NOACTIVATEANDEAT = 4;

  private static readonly IntPtr HWND_TOPMOST = (IntPtr)(-1);

  private const int SWP_NOSIZE = 0x0001;
  private const int SWP_NOMOVE = 0x0002;
  private const int SWP_NOACTIVATE = 0x0010;

  [DllImport("user32.dll")]
  [return: MarshalAs(UnmanagedType.Bool)]
  private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter,
    int X, int Y, int cx, int cy, int uFlags);

  public PopupForm()
  {
    SetStyle(ControlStyles.Selectable, false);
    FormBorderStyle = FormBorderStyle.None;
    StartPosition = FormStartPosition.Manual;
    ShowInTaskbar = false;
    Visible = false;
  }

  protected override CreateParams CreateParams
  {
    get
    {
      CreateParams cp = base.CreateParams;
      cp.Style |= WS_POPUP | WS_BORDER;
      cp.ExStyle |= WS_EX_TOPMOST | WS_EX_NOACTIVATE;
      return cp;
    }
  }

  protected override bool ShowWithoutActivation
  {
    get { return true; }
  }

  protected override void WndProc(ref Message m)
  {
    if (m.Msg == WM_MOUSEACTIVATE)
    {
      OnClick(EventArgs.Empty);
      m.Result = (IntPtr)MA_NOACTIVATEANDEAT;
    }
    else
      base.WndProc(ref m);
  }

  public new void Show()
  {
    Windows.SetWindowPos(Handle, HWND_TOPMOST, 0, 0, 0, 0,
      SWP_NOACTIVATE | SWP_NOSIZE | SWP_NOMOVE);
    base.Show();
  }
}