How to get all children of a parent control?

Maybe it could be useful for someone:

public void GetControlsCollection(Control root,ref List<Control> AllControls,  Func<Control,Control> filter)
{
    foreach (Control child in root.Controls)
    {
        var childFiltered = filter(child);
        if (childFiltered != null) AllControls.Add(child);
        if (child.HasControls()) GetControlsCollection(child, ref AllControls, filter);
    }
}

This is recursive function to get the collection of controls with the possibility of appling filter (for expample by type). And the example:

 List<Control> resultControlList = new List<Control>();
 GetControlsCollection(rootControl, ref resultControlList, new Func<Control,Control>(ctr => (ctr is DropDownList)? ctr:null ));

It will return all DropDownLists in rootControl and his all children

Controls have a MyControl.Controls collection which you can do a foreach on.

Each Control also has a Parent property which gives you the parent control.

You can write a recursive method if you need to go down an unknown number of levels.

If you only want the immediate children, use

...
var children = control.Controls.OfType<Control>();
...

If you want all controls from the hierarchy (ie, everything in the tree under a certain control), use a pretty simple data-recursive method:

    private IEnumerable<Control> GetControlHierarchy(Control root)
    {
        var queue = new Queue<Control>();

        queue.Enqueue(root);

        do
        {
            var control = queue.Dequeue();

            yield return control;

            foreach (var child in control.Controls.OfType<Control>())
                queue.Enqueue(child);

        } while (queue.Count > 0);

    }

Then, you might use something like this in a form:

    private void button1_Click(object sender, EventArgs e)
    {
        /// get all of the controls in the form's hierarchy in an IEnumerable<>
        foreach (var control in GetControlHierarchy(this))
        {
            /// do something with this control
        }
    }