Difference between ‘string’ and ‘System.String’ in C#

‘string’ is an alias (or shorthand) of System.String. That means, by typing ‘string’ we meant System.String. As pointed out by Jeffrey Richter (in his book CLR via C#, page 119), it’s as if every C# program (in Visual Studio) contained ‘using’ directives like the following:

1 using string = System.String;
2 using char = System.Char;
3 using int = System.Int32;
4 using double = System.Double;