I usually use something like this for various reasons throughout an application:
if (String.IsNullOrEmpty(strFoo)) { FooTextBox.Text = \"0\"; } else {
Old question, but thought I'd add this to help out,
#if DOTNET35 bool isTrulyEmpty = String.IsNullOrEmpty(s) || s.Trim().Length == 0; #else bool isTrulyEmpty = String.IsNullOrWhiteSpace(s) ; #endif