Code-Sage

C# language feature:

  • Extension methods

applies to

  • objects

benefit

  • Enables “adding” methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type.

how to use

  • 1) Declare namespace in new class file with desired name.
  • 2) Declare a public static class with desired name.
  • 3) Declare a method and precede the first parameter of class being extended with this keyword.
  • 4) Add using namespace and reference extension method on class being “extended”.
  • 5) Declare and call the extended method.

Notes

  • Extension methods must have unique method signatures not available in original type. Use extension methods sparingly. Prefer extending via inheritance.

example:

    namespace CodeSage.ExtensionMethod // 1) Declare namespace in new class file.
    {   
        // 2) Declare a `public static class` with desired name. 
        public static class Extension_Method_Example 
        {
            // 3) Declare a method and precede the first parameter of class being extended with `this` keyword.
            static public bool HasSpace(this String str)  // String is the class being extended
            {
                return !(str.IndexOf(' ') == -1);
            }
        }
    }

    // to use an extension method

    namespace CodeSage.ExtensionUse
    {
        // 4) Add using namespace and reference extension method on class being "extended".
        using CodeSage.ExtensionMethod;

        public class Use_of_Extension_Method
        {
            public void test()
            {
                String sometext = "Hi I have a space"; // 5) Declare and Call the extended method
                bool result = sometext.HasSpace(); 
            }
        }
    }
C# articles

csharp v2 +

Anonymous methods * Co- and Contra-variance for delegates * Delegate inference * Generics * Getter and setter separate accessibility * Iterators * Method group conversions (delegates) * Nullable types * Partials * Static classes *

csharp v3 +

Anonymous types * Auto-Implemented properties * Expression trees * Extension methods * Implicitly typed local variables * Lambda expression * Object and collection initializers * Partial methods * Query expressions *

csharp v4 +

Generic co- and contravariance * Named and optional arguments *

csharp v5 +

Asynchronous methods * Caller info attributes *

csharp v6 +

A note for CSharp 6 and beyond * Allow await in catch and finally blocks * Auto property initializers * Default values for Read-only Auto-properties * Dictionary (index) initializers * Exception filters * Expression-bodied members * Import of static type members into namespace * Null propagator (null-conditional operator, succinct null checking) * String interpolation * nameof operator *

csharp v7 +

Binary literals * Deconstruction * Digit separators * Expression bodied constructors and finalizers * Expression bodied getters and setters * Generalized async return types * Local functions * Out variables * Pattern matching * Ref returns and locals * Tuples *