C#委托基础

介绍

使用

普通委托详解

        static void Main(string[] args)
        {
            int x = 100;
            int y = 300;

            //Get the pointer of the function "ToStirng" and apply it to the varible getAString
            GetAString getAString = new GetAString(x.ToString);
            GetAString getAString2 = x.ToString;//2nd Way to define: same as above
            Console.WriteLine(getAString());//Usable while calling by varible "getAString"
            Console.WriteLine(getAString2());//Usable while calling by varible "getAString2"

            string str = getAString.Invoke();//2nd way to call
            string str2 = getAString2.Invoke();//2nd way to call
            Console.WriteLine(str);
            Console.WriteLine(str2);

            MethodHolder myMethod = new MethodHolder(y.ToString);
            Console.WriteLine(AnotherMethod(myMethod));
        }


        //Signature of the delegate
        delegate void VoidFuncWithOneParameter(int parameter);
        delegate int IntFuncWithOneParameter(int parameter);
        delegate int IntFuncWithTwoParameters(int parameterInt, string parameterStr);

        delegate string GetAString();//This will be treated as a class


        /*!IMPORTANT!*/
        delegate string MethodHolder();

        //delegate can be used to send a method as parameter to another method
        static string AnotherMethod(MethodHolder method)
        {
            return method();//just like a callback-function in JS
        }

Action委托详解

        static void Main(string[] args)
        {
            //Action is a delegate which points to a void method without parameters 
            Action voidMethod = Method;
            voidMethod();

            //Action<type of parameter> can  points to a void method with parameters 
            Action<int> voidMethodWithParameters = MethodWithParameters;
            voidMethodWithParameters(5);
        }

        static void Method()
        {
            Console.WriteLine("This is a method which returns nothing.");
        }

        static void MethodWithParameters(int parameter)
        {
            if (parameter > 0)
            {
                for (int i = 0; i < parameter; i++)
                {
                    Console.WriteLine("This is a void method with a parameter.");
                }
            }
            else
            {
                Console.WriteLine("Parameter should be greater than 0");
            }
        }

Func委托详解

与Action委托不同的是，Func委托可以代理具有返回值的方法。

       static void Main(string[] args)
        {
            //The last parameter in "Func" is the type of return-value the method
            //while the former parameters are all the parameters' type of the target method 
            Func<string, int, bool, float> matureMethod = MatureMethod;
            matureMethod("Hello world!", 6, true);

            //The single parameter means the return-value of the method
            Func<bool> simpleMethod = SimpleMethod;
            Console.WriteLine(simpleMethod());
        }

        static float MatureMethod(string parameterStr, int parameterInt, bool parameterBool)
        {
            if (parameterBool && parameterInt > 0)
            {
                for (int i = 0; i < parameterInt; i++)
                {
                    Console.WriteLine($"{i} : {parameterStr}");
                }
                return 0.618f;
            }
            else
            {
                Console.WriteLine("3rd parameter is set to false or the 2nd parameter is smaller than 0");
                return 3.14f;
            }
        }

        static bool SimpleMethod()
        {
            return true;
        }

多播委托

作者：艾孜尔江；转载或使用请标明出处。