C # the usage of Action and Func,

C # the usage of Action and Func,

In the past, I used to define a delegate to write the delegate, but recently I have seen that some foreigners write the source code in the action and func modes, at that time, I felt unfamiliar with the source code, so I took the time to learn the two methods and found that the code was indeed concise. We can also use these two methods in practice.

Let's talk about delegation:

Simulate the scenario: James has a high learning mood recently. He has never been able to satisfy his desire to buy books (a programmer's self-cultivation ). But in the past, I used to run a book factory to buy it. nm was too far away to handle it. I went to a nearby bookstore to buy it. James went to give the money and got a book back. This process was commissioned. Start Analysis

1: James wants to buy a self-developed programmer book (xx books won't be bought). Hard requirements (this is to define the nature of delegation)

Code:

Private delegate void BuyBook ();

2: nearby bookstore (delegated method)

Code:

Public static void Book ()
{
Console. WriteLine ("I provide books ");
}

3: Relationship between Xiao Ming and Bookstore (delegate binding method)

Code:

BuyBook buybook = new BuyBook (Book );

4: James give money to get a book (trigger)

Buybook ();

The above content is to understand the delegate usage. Next I will explain the actions and Func

Action usage

1: James is very upset. I just bought a book. Every time I define it, I get bored. Is there a way not to define the Commission, the Action we are talking about today

Action BookAction = new Action(Book);            BookAction();

Is this much simpler?

2: James is not satisfied now. I have finished reading a programmer's self-cultivation. Now I want to buy another book. What should I do? Should I re-define the Commission. In fact, you don't need to pass through the parameters. Next, let's take a look at the usage of Action <T>.

Static void Main (string [] args) {Action <string> BookAction = new Action <string> (Book); BookAction ("Hundred Years of loneliness ");} public static void Book (string BookName) {Console. writeLine ("I bought books: {0}", BookName );}

3: Now James has changed his mind. Not only do I have to choose books myself, but I have to buy books from a great book manufacturer. Is there any way to do this, action <in T1, in T2>

 

Static void Main (string [] args) {Action <string, string> BookAction = new Action <string, string> (Book); BookAction ("Hundred Years of loneliness ", "Beijing Bookstore");} public static void Book (string BookName, string ChangJia) {Console. writeLine ("I bought books: {0} from {1}", BookName, ChangJia );}

Func usage

James has another question. Every time I go to the bookstore to get a book, is there a way to send it directly to my house? Then Func provides such a service?

Func encapsulates a method that may not have parameters (maybe not) but returns the type value specified by the TResult parameter.

1: Let's first look at a method with no parameters but return values.

Static void Main (string [] args) {Func <string> RetBook = new Func <string> (FuncBook); Console. writeLine (RetBook);} public static string FuncBook () {return "sent a book ";}

2: Methods with parameters and return values

static void Main(string[] args){Func<string,string> RetBook = new Func<string,string>(FuncBook);Console.WriteLine(RetBook);}public static string FuncBook(string BookName){return BookName;}

3: A very important use of Func is to pass the value. Here is a simple code to describe it.

Func <string> funcValue = delegate {return "I am the value to be passed 3" ;}; DisPlayValue (funcValue );

Note 1: DisplayVaue refers to the processing of incoming values, such as cache processing, or unified addition of databases.

Private static void DisPlayValue (Func <string> func) {string RetFunc = func (); Console. writeLine ("I'm testing the passed value: {0}", RetFunc );}

Summary

1: Action is used for methods without return values (parameters can be passed as needed)

2: The opposite of Func is used for methods with returned values (the same parameter is based on your own situation)

3: Remember to use action if there is no return, and Func if there is a return