Find all child controls of specific type using Enumerable.OfType() or LINQ

Question

Existed MyControl1.Controls.OfType() searches only thru initial collection and do not enters to children.

Is it possible to find all

Answer 1

To improve above answer it would make sense to change the return type to

//Returns all controls of a certain type in all levels:
public static IEnumerable<TheControlType> AllControls<TheControlType>( this Control theStartControl ) where TheControlType : Control
{
   var controlsInThisLevel = theStartControl.Controls.Cast<Control>();
   return controlsInThisLevel.SelectMany( AllControls<TheControlType> ).Concat( controlsInThisLevel.OfType<TheControlType>() );
}

//(Another way) Returns all controls of a certain type in all levels, integrity derivation:
public static IEnumerable<TheControlType> AllControlsOfType<TheControlType>( this Control theStartControl ) where TheControlType : Control
{
   return theStartControl.AllControls().OfType<TheControlType>();
}

Answer 2

I use this generic recursive method:

The assumption of this method is that if the control is T than the method does not look in its children. If you need also to look to its children you can easily change it accordingly.

public static IList<T> GetAllControlsRecusrvive<T>(Control control) where T :Control 
{
    var rtn = new List<T>();
    foreach (Control item in control.Controls)
    {
        var ctr = item as T;
        if (ctr!=null)
        {
            rtn.Add(ctr);
        }
        else
        {
            rtn.AddRange(GetAllControlsRecusrvive<T>(item));
        }

    }
    return rtn;
}

Answer 3

I use an extension method to flatten control hierarchy and then apply filters, so that's using own recursive method.

The method looks like this

public static IEnumerable<Control> FlattenChildren(this Control control)
{
  var children = control.Controls.Cast<Control>();
  return children.SelectMany(c => FlattenChildren(c)).Concat(children);
}