Various delegates in. NET (Delegate, Action, Func)

1, Delegate, commissioned by the originator

        protected Delegate intClassdelegate (intXinty);//defining delegate types and Parameters        Static voidMain (string[] args) {classdelegate dele=NewClassdelegate (ADD);//instantiate a delegateConsole.WriteLine (Dele (1,2));//Invoke DelegateConsole.readkey (); }        Static intADD (intAintb) {returnA +b; }

2. Action, you can pass in parameters, no delegate with return value

Method 1, calling the method

        Static voidMain (string[] args) {Action<int,int> AC =Newaction<int,int> (Showaddresult);//instantiate a delegateAc1,2);//Invoke DelegateConsole.readkey (); }        Static voidShowaddresult (intAintb) {Console.WriteLine (a+b); }

Method 2, using a lambda expression

        Static void Main (string[] args)        {            Action<intint> AC = ((p, q) + = Console.WriteLine (p + q)); // instantiate a delegate            AC (12); // Invoke Delegate             Console.readkey ();        }

Method 3, as a parameter

        Static voidMain (string[] args) {Action<string> ac = (p = Console.WriteLine ("I am method 1, passing in the value:"+P));//instantiate a delegateaction<string> AC2 = (p = Console.WriteLine ("I am method 2, passing in the value:"+ p));//instantiate another delegateTest (AC,"parameter 1");//call the test method, passing in the delegate parameterTest (AC2,"parameter 1");//call the test method, passing in the delegate parameterConsole.readkey (); }        Static voidTest<t> (action<t>AC, T Inputparam)        {AC (Inputparam); }

3, Func, can pass in parameters, must have a return value of the delegate

Method 1, calling the method

        Static voidMain (string[] args) {Func<string> FC1 =Newfunc<string> (Showaddresult);//instantiate a delegate            stringresult = FC1 ();//Invoke DelegateConsole.WriteLine (Result);        Console.readkey (); }        Static stringShowaddresult () {return "the earth is round."; }

Method 2, using a lambda expression

        Static voidMain (string[] args) {            //instantiate a delegate, pay attention to the parentheses, write the value is the return value, cannot take returnfunc<string> FC1 = () ="the earth is round."; //instantiate another delegate, note that you can write multiple lines of code after the parentheses, but you must bring a returnfunc<string> FC2 = () =            {                return "the earth is round.";            }; stringresult = FC1 ();//Invoke Delegate            stringRESULT2 = FC2 ();//Invoke DelegateConsole.WriteLine (Result);            Console.WriteLine (RESULT2);        Console.readkey (); }

Method 3, as a parameter

        Static voidMain (string[] args) {            //instantiate a delegate, pay attention to the parentheses, write the value is the return value, cannot take returnfunc<int,string> FC1 = (p) = ="Incoming Parameters"+ P +", the earth is round."; //instantiate another delegate, note that you can write multiple lines of code after the parentheses, but you must bring a returnfunc<string,string> FC2 = (p) = =            {                return "Incoming Parameters"+ P +", the earth is round.";            }; stringresult = test<int> (FC1,1);//Invoke Delegate            stringRESULT2 = test<string> (FC2,"1");//Invoke DelegateConsole.WriteLine (Result);            Console.WriteLine (RESULT2);        Console.readkey (); }        Static stringTest<t> (Func<t,string>FC, T Inputparam) {            returnFC (Inputparam); }

Summarize:

Delegate at least 0 parameters, up to 32 parameters, can have no return value, or you can specify a return value type

Func can accept 0 to 16 incoming parameters and must have a return value

Action can accept 0 to 16 incoming parameters, no return value

Various delegates in. NET (Delegate, Action, Func)