Optimizing the ControlCollection Extension Method

got a question about an extension method I wrote that looks like this:

public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class
{

    T control;

    foreach (Control ctrl in instance)
    {
        if ((control = ctrl as T) != null)
        {
            yield return control;
        }

        foreach (T child in FindControlsOfType<T>(ctrl.Controls))
        {
            yield return child;
        }
    }

}

public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class
{
    return FindControlsOfType<T>(instance).Where(match);
}

      

        
        
        
      

    

The idea here is to find all the controls that match the specificc criterion (hence Func <..>) in the controls collection. My question is:

The second method (which has a Func) first calls the first method to find all controls of type T and then does the where clause or does a "runtime" call optimization to satisfy the where clause on the "whole" enum (if you understand what I have in mind).

secondly, are there any other optimizations I can make to make the code work better.

An example might look like this:

var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>(
                                ctrl => ctrl.CustomProperty == "Test"
                                )
                                .FirstOrDefault();