ToolTip.Show for an inactive window doesn't works

Question

Why tooltip, displayed manually with ToolTip.Show, is not shown, when window, containing control, is inactive?

public class MyControl : Button
{

    private _tip;
    public string ToolTip
    {
        get { return _tip; }
        set { _tip = value; }
    }

    private ToolTip _toolTip = new ToolTip();

    public MyControl()
    {
        _toolTip.UseAnimation = false;
        _toolTip.UseFading = false;
        _toolTip.ShowAlways = true;
    }

    protected override void OnMouseHover(EventArgs e)
    {
        _toolTip.Show(_tip, this, 0, Height);
        base.OnMouseHover(e);
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        _toolTip.Hide(this);
        base.OnMouseLeave(e);
    }
}

I went for ToolTip.Show because I must have tooltip onscreen for unlimited time, which is not possible with normal ToolTip. I also love the idea of having tooltip text as a part of control itself. But unfortunately, when showing tooltip this way for inactive window (despite ShowAlways = true), it simply doesn't work.

The OnMouseHower event is rised, but _toolTip.Show does nothing.. unless window is activated, then everything works.

Bounty

Adding bounty for a solution to display tooltip for an inactive form (preferably with solution when tooltip text is a property of control, not IContainer).

Answer 1

There is a private method that does what you want, so to access it, you would have to use reflection to call it:

using System.Reflection;

public class MyControl : Button {
  private ToolTip toolTip = new ToolTip() {
    UseAnimation = false,
    UseFading = false
  };

  public string ToolTip { get; set; }

  protected override void OnMouseHover(EventArgs e) {
    base.OnMouseHover(e);
    Point mouse = MousePosition;
    mouse.Offset(10, 10);
    MethodInfo m = toolTip.GetType().GetMethod("SetTool",
                           BindingFlags.Instance | BindingFlags.NonPublic);
    m.Invoke(toolTip, new object[] { this, this.ToolTip, 2, mouse });
  }

  protected override void OnMouseLeave(EventArgs e) {
    base.OnMouseLeave(e);
    toolTip.Hide(this);
  }
}

The tip will display on an inactive window and it will stay on the screen indefinitely until the mouse moves off the control.