C Sharp Syntax - Extension Methods

Extension Methods

This is a feature of C# 3.0.

Extension methods are a form of syntactic sugar providing the illusion of adding new methods to the existing class outside its definition. In practice, an extension method is a static method that is callable as if it were an instance method; the receiver of the call is bound to the first parameter of the method, decorated with keyword this:

public static class StringExtensions { public static string Left(this string s, int n) { return s.Substring(0, n); } } string s = "foo"; s.Left(3); // same as StringExtensions.Left(s, 3);

See also

• Decorator pattern