I have an IEnumerable<T> method that I'm using to find controls in a WebForms page.

The method is recursive and I'm having some problems returning the type I want when the yield return is returnig the value of the recursive call.

My code looks as follows:

public static IEnumerable<Control> GetDeepControlsByType<T>(this Control control) { foreach(Control c in control.Controls) { if (c is T) { yield return c; } if(c.Controls.Count > 0) { yield return c.GetDeepControlsByType<T>(); } } }

This currently throws a "Cannot convert expression type" error. If however this method returns type IEnumerable<Object> , the code builds, but the wrong type is returned in the output.