如何在父窗口（开启器）中相对于控件的位置显示模态窗体

Question

Well, I have a form that I open using:

ShowDialog(this);

I try to change the position of the form using its Location property, but I don't understand what exactly is this position relative to? I want to open this form below a certain button. So how can this be done?

Thanks.

Answer 1

A Form will expect the co-ordinates relative to the screen's top-left corner. However, the location of a Control within a Form is relative to the top-left corner of the form ^† .

Use the Control's Location property to find its location, and then call PointToScreen on the Form object to turn it into screen co-ordinates. Then you can position the new form relative to that.

For example:

var locationInForm = myControl.Location;
var locationOnScreen = mainForm.PointToScreen(locationInForm);

using (var model = new ModelForm())
{
    model.Location = new Point(locationOnScreen.X, locationOnScreen.Y + myControl.Height + 3);
    model.ShowDialog();
}

---

^† Actually the top-left corner of the client area of the form.

Answer 2

我更喜欢这个：

myModalForm.Location = New Point(myControl.PointToScreen(Point.Empty).X + myControl.Width, myControl.PointToScreen(Point.Empty).Y)