Object-oriented Fundamentals (vii)

Commissioned

Delegation is a new object-oriented language feature that has not been seen in the long history of object-oriented languages such as C + +. Microsoft introduced this feature when designing object-oriented languages that run on the. NET Framework platform.

1. Concept:

A delegate can be thought of as a "container" of a function, and it can be used as a function after "loading" a specific function. A delegate variable can be thought of as a type-safe function pointer that can receive only the address of a function that meets its requirements.

2, definition method:delegate keyword. Cases:

    int Mydele (int b);

3, using the delegate call function

(1) First define a class, which writes a few methods:

    ClassClass1 {Publicint Jiafa (int A,Intb) {Return a +b }Publicint Jianfa (int A, int b) {return a- b; }  }

(2) calling a function through a delegate:

Mydele m;Defines a variable m = of an existing delegate typeNew Class1 (). Jiafa;Assign a value to the above variable Console.WriteLine (m (1,2//result is 3m = new Class1 (). JIANFA; Console.WriteLine (M (1,2)); //result is-1       

4. Note: A variable of a delegate type can refer to any function that satisfies its requirements.

5, the extension of the delegation:

(1) Special delegate generic set, anonymous delegate

func<Stringstring> MyFunc =new Class1 (). returnstring; // input string, Output Stringconsole.writeline (MyFunc (" Zhang San "));     

(2) Direct writing method

func<StringString> Newfunc =DelegateStrings) {return S + "world! "; }; Console.WriteLine (Newfunc ( " John Doe "));

(3) Lambda method simple version 1, replace delegate with s=> (string s)

func<Stringstring> newfunc1 = S=> {return s +  "world! ";}; 

(4) Lambda method simple version 2, two parameters

func<StringStringString> Newfunc2 = (S1,S2) +{ return s1 + "world!" +S2;}; 

(5) Lambda method simple version 3, remove curly braces, direct write method

func<string,string> newfunc3 = (S1, s2) =>s1+"world!" +S2; Console.ReadLine ();    

Object-oriented Fundamentals (vii)