Selecting form controls that are either inside or outside a rectangle

Question

I have a function which loops over the controls on a form and checks to see if it's in a given rect, and then adds it or doesn't add it to a list<>. The parameter bContained is used to determine if we want a list of "in the rect" or "not in the rect" controls.

List<Control> getControls(Control container, Rectangle rect, bool bContained = false)
{
    List<Control> Selected = new List<Control>();

    rect = RectangleToClient(rect);

    foreach (Control ctl in container.Controls)
    {
        //Do we want selected or non-selected controls
        if (bContained)
        {
            if (rect.IntersectsWith(ctl.Bounds)) Selected.Add(ctl);
            foreach (Control ct in ctl.Controls) Selected.Add(ct);
        }
        else
        {
            if (!rect.IntersectsWith(ctl.Bounds)) Selected.Add(ctl);
            foreach (Control ct in ctl.Controls) Selected.Add(ct);
        }
    }

    return Selected;
}

Answer 1

You have an error there, unless you wanted to include all child controls regardless of whether they're contained. It should be:

if (rect.IntersectsWith(ctl.Bounds)) 
{    
    Selected.Add(ctl);
    foreach (Control ct in ctl.Controls) 
    {
        Selected.Add(ct);
    }
}

As for the test, instead of two cases you can use:

if(rect.IntersectsWith(ctl.Bounds) == bContained)

Answer 2

You can make things more concise with LINQ. Here's one way that should work:

List<Control> getControls(Control container, Rectangle rect, bool bContained = false)
{
    rect = RectangleToClient(rect);
    return (from Control ctl in container.Controls
                  where rect.IntersectsWith(ctl.Bounds) == bContained                     
                  select new List<Control> { ctl }.Union(ctl.Controls.OfType<Control>()))
                  .SelectMany(x => x).ToList();
}

This basically does the same thing, filters the collection according to bContained. Creates a collection of lists that each contain the parent control and its sub-controls. Then flattens them into one list.