C# Get a control's position on a form

Question

Is there any way to retrieve a control\'s position in a form, when the control may be inside other controls (like Panels)?

The control\'s Left and Top properties giv

Answer 1

Supergeek, your non recursive function did not producte the correct result, but mine does. I believe yours does one too many additions.

private Point LocationOnClient(Control c)
{
   Point retval = new Point(0, 0);
   for (; c.Parent != null; c = c.Parent)
   { retval.Offset(c.Location); }
   return retval;
}

Answer 2

In my testing, both Hans Kesting's and Fredrik Mörk's solutions gave the same answer. But:

I found an interesting discrepancy in the answer using the methods of Raj More and Hans Kesting, and thought I'd share. Thanks to both though for their help; I can't believe such a method is not built into the framework.

Please note that Raj didn't write code and therefore my implementation could be different than he meant.

The difference I found was that the method from Raj More would often be two pixels greater (in both X and Y) than the method from Hans Kesting. I have not yet determined why this occurs. I'm pretty sure it has something to do with the fact that there seems to be a two-pixel border around the contents of a Windows form (as in, inside the form's outermost borders). In my testing, which was certainly not exhaustive to any extent, I've only come across it on controls that were nested. However, not all nested controls exhibit it. For example, I have a TextBox inside a GroupBox which exhibits the discrepancy, but a Button inside the same GroupBox does not. I cannot explain why.

Note that when the answers are equivalent, they consider the point (0, 0) to be inside the content border I mentioned above. Therefore I believe I'll consider the solutions from Hans Kesting and Fredrik Mörk to be correct but don't think I'll trust the solution I've implemented of Raj More's.

I also wondered exactly what code Raj More would have written, since he gave an idea but didn't provide code. I didn't fully understand the PointToScreen() method until I read this post: http://social.msdn.microsoft.com/Forums/en-US/netfxcompact/thread/aa91d4d8-e106-48d1-8e8a-59579e14f495

Here's my method for testing. Note that 'Method 1' mentioned in the comments is slightly different than Hans Kesting's.

private Point GetLocationRelativeToForm(Control c)
{
  // Method 1: walk up the control tree
  Point controlLocationRelativeToForm1 = new Point();
  Control currentControl = c;
  while (currentControl.Parent != null)
  {
    controlLocationRelativeToForm1.Offset(currentControl.Left, currentControl.Top);
    currentControl = currentControl.Parent;
  }

  // Method 2: determine absolute position on screen of control and form, and calculate difference
  Point controlScreenPoint = c.PointToScreen(Point.Empty);
  Point formScreenPoint = PointToScreen(Point.Empty);
  Point controlLocationRelativeToForm2 = controlScreenPoint - new Size(formScreenPoint);

  // Method 3: combine PointToScreen() and PointToClient()
  Point locationOnForm = c.FindForm().PointToClient(c.Parent.PointToScreen(c.Location));

  // Theoretically they should be the same
  Debug.Assert(controlLocationRelativeToForm1 == controlLocationRelativeToForm2);
  Debug.Assert(locationOnForm == controlLocationRelativeToForm1);
  Debug.Assert(locationOnForm == controlLocationRelativeToForm2);

  return controlLocationRelativeToForm1;
}

Answer 3

I usually do it like this.. Works every time..

var loc = ctrl.PointToScreen(Point.Empty);

Answer 4

Oddly enough, PointToClient and PointToScreen weren't ideal for my situation. Particularly because I'm working with offscreen controls that aren't associated with any form. I found sahin's solution the most helpful, but took out recursion and eliminated the Form termination. The solution below works for any of my controls visible or not, Form-contained or not, IContainered or not. Thanks Sahim.

private static Point FindLocation(Control ctrl)
{
    Point p;
    for (p = ctrl.Location; ctrl.Parent != null; ctrl = ctrl.Parent)
        p.Offset(ctrl.Parent.Location);
    return p;
}

Answer 5

private Point FindLocation(Control ctrl)
{
    if (ctrl.Parent is Form)
        return ctrl.Location;
    else
    {
        Point p = FindLocation(ctrl.Parent);
        p.X += ctrl.Location.X;
        p.Y += ctrl.Location.Y;
        return p;
    }
}

Answer 6

I usually combine PointToScreen and PointToClient:

Point locationOnForm = control.FindForm().PointToClient(
    control.Parent.PointToScreen(control.Location));