A string is null if it has not been assigned a value (in C++ and Visual Basic) or if has explicitly been assigned a value of null. Although the composite formatting feature can gracefully handle a null string, as the following example shows, attempting to call one if its members throws a NullReferenceException.
A string is empty if it is explicitly assigned an empty string ("") or String.Empty. An empty string has a Length of 0. The following example creates an empty string and displays its value and its length.
Universal Windows Platform Available since 4.5 .NET Framework Available since 2.0 Portable Class Library Supported in: portable .NET platforms Silverlight Available since 2.0 Windows Phone Silverlight Available since 7.0 Windows Phone Available since 8.1