Delegate, Lambda expression, event series 01, Delegate, basic delegate usage, delegate method and Target attribute

A delegate is a class.

namespace ConsoleApplication1
{
    internal delegate void MyDelegate(int val);
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
}

Use reflector to view the delegate il code:

○ Delegate is indeed a class
○ Delegate constructor receiver method and class instance
○ It is also a multicast delegate and can be assigned a value using ++ =.
○ Delegate internal use of the invoke Method for triggering
○ Begininvoke and endinvoke methods are used in multithreading scenarios.

 

Next, we will experience how to use the delegate and what the delegate's method and target attributes represent.

namespace ConsoleApplication1
{
    internal delegate void MyDelegate(int val);
    class Program
    {
        static void Main(string[] args)
        {
// Delegate and static methods
            MyDelegate d = new MyDelegate(M1);
            d(10);
            Console.WriteLine(d.Method);
            if (d.Target == null)
            {
Console. writeline ("The current delegate calls static methods without class instances ");
            }
            else
            {
Console. writeline ("The current delegate calls an instance method, and the class instance is:" + D. Target );
            }
            Console.WriteLine("-------------------");
            
// Delegate and instance methods
            Program p = new Program();
            d = p.M2;
            d.Invoke(10);
            Console.WriteLine(d.Method);
            if (d.Target == null)
            {
Console. writeline ("The current delegate calls static methods without class instances ");
            }
            else
            {
Console. writeline ("The current delegate calls an instance method, and the class instance is:" + D. Target );
            }
        }
        static void M1(int val)
        {
Console. writeline ("I Am a static method, output" + val );
        }
        void M2(int val)
        {
Console. writeline ("I am an instance method, output" + val );
        }
    }
}

○ Create a delegate: Use the Delegate constructor, new mydelegate (M1), or D = P. m2, which is a method of writing "syntactic sugar", also calls the Delegate constructor internally.
○ Delegate and static methods: You can pass the static method to the Delegate constructor as long as the parameter list and return type are the same.
○ Delegate and instance methods: You can pass the instance method to the Delegate constructor as long as the parameter list and return type are the same.
○ Delegated call: for example, D. invoke (10), called through the entrusted instance method invoke; like D (10), this is a "syntax sugar" method, which also calls the instance method invoke internally.
○ Target attribute: indicates the name of the class instance to which the instance method belongs. If it is a static method, target is null.
○ Method attribute: The method represented by the delegate, which may be a static method or an instance method.

Delegate, Lambda expression, event series 01, Delegate, basic delegate usage, delegate method and Target attribute