Why would you use the using statement this way in ASP.NET?

Question

Refactoring some code again. Seeing some of this in one of the ASP.NET pages:

using (TextBox txtBox = e.Row.Cells[1].FindControl("txtBox") as TextBox)
{
}

There is no need to dispose txtBox, because it's just a reference to an existing control. And you don't want the control disposed at all. I'm not even sure this isn't harmful - like it would appear to ask for the underlying control to be disposed inappropriately (although I have not yet seen any ill effects from it being used this way).

Answer 1

TextBox inherits its implementation of IDisposable from its Component superclass. That implementation removes the component from its site container if it has one.

So, doing that might have nefarious effects if the text box actually resides in a site container. Also, after calling Dispose() on an object, you should not use it again, no matter what (it's not in a usable state anymore).

I'd suggest you avoid that pattern with ASP.NET web controls.