Looping through the page to work on all the control of similar type -

Of late I have found this one question related to finding controls inside the page dynamically and apply some similar function to them. Like put a css class to all the textbox (or for that matter any control) in a page. Remember a page can have textbox as a control directly under it, or the textbox can be inside another composite control (like login control, gridview, detailview) inside the page.