All the highlighted solutions are using recursion (which is performance costly). Here is cleaner way without recursion:
public T GetControlByType<T>(Control root, Func<T, bool> predicate = null) where T : Control
{
if (root == null) {
throw new ArgumentNullException("root");
}
var stack = new Stack<Control>(new Control[] { root });
while (stack.Count > 0) {
var control = stack.Pop();
T match = control as T;
if (match != null && (predicate == null || predicate(match))) {
return match;
}
foreach (Control childControl in control.Controls) {
stack.Push(childControl);
}
}
return default(T);
}