Object-oriented design patterns and delegates

Factory mode

     Public classJisuan {Private intA;  Public intA {Get{returnA;} Set{a =value;} }        Private intb;  Public intB {Get{returnb;} Set{b =value;} }         Public Virtual intYunsuan () {return 0; }    }    //Addition Class     Public classJia:jisuan { Public Override intYunsuan () {return Base. A +Base.        B }    }    //Subtraction Class     Public classJian:jisuan { Public Override intYunsuan () {return Base. ABase.        B }    }    //Factory class     Public classGongchang { Public StaticJisuan Duixiang (strings) {Switch(s) { Case "+":                    return NewJia ();  Break;  Case "-":                    return NewJian ();  Break;  Case "*":                    return NewCheng ();  Break; default:                    return NewJia ();  Break; }        }    }

Single-Case mode

    classDbda {//Build Variables         Public stringhost;  Public stringdatabase; //a static member that is used to store the object of the class         Public StaticDBDA db =NULL; //construct method to let the class not be instantiated        PrivateDbda () {}//provide a way to create objects, control only one object         Public StaticDbda Duixiang ()//because I can't make objects, I use static .        {            if(db = =NULL) {db=NewDbda (); }            returnDB; }    }    classProgram {Static voidMain (string[] args) {DBDA db=Dbda.            Duixiang (); Db.host="localhost"; Dbda DB1=Dbda.                        Duixiang ();                        Console.WriteLine (Db1.host);        Console.ReadLine (); }    

Commissioned
Also known as a proxy, an event is also a delegate
Defined at the outermost of the class

1. Define the delegate
Keyword: delegate
function Signature : signature and function remain consistent
When defining a delegate, you define it according to the function.
public delegate int first (int a,int b);
The return type of the method pointed to requires the parameters to be consistent!

2. Defining the delegate variable, pointing to the method

A delegate cannot be instantiated because it is not a class

First F = new Jiafa (). Jiafa; New delegate variable, point to method, note!! method does not need parentheses!!

The second time you can use + =

public int Jiafa (int a,int b)
{
return a+b;
}

Call:
f (5,3);

Can be understood as a pointer to a function, which function the delegate points to, which function is represented by the delegate
Allows functions to be passed as arguments

    //Defining Delegates     Public Delegate voidSuibian (strings); classProgram {Static voidMain (string[] args) {            //Delegate//parameterization of the methodSuibian s =China ; S+ = America;//+ = is the binding method = minus a method//calling a speech methodSpeak (s);            Console.WriteLine ();        Console.ReadLine (); }        //methods of speech function        Static voidSpeak (Suibian yu) {yu ("Zhang San"); }        //Voice Pack         Public Static voidAmerica (strings) {Console.WriteLine (S+"Hello"); }        Static voidChina (strings) {Console.WriteLine (S+"Hello"); }        Static voidHanyu (strings) {Console.WriteLine (S+"Bjdkaj"); }      }

※ Event

Events are a special kind of delegate

Object-oriented design patterns and delegates