C# delegate implements callback mechanism (primary understanding)

/*

Delegates implement callbacks: the mechanism of
    passing callbacks with methods as parameters through delegates
    : from calling side -> definition side -> calling side -> definition side -> calling side

    The caller executes the method (the method parameter contains the entrusted type) -> 
    enters the definition method port, executes the code block in the method, executes to the entrusted method ->
    returns to the caller to execute the passed method parameter ->
    returns to the definition end and continues to execute The code block ->
    return to the caller after execution

*/

class TestCallBack
{     TesHandler handler =new TesHandler();     //1. Execute the method (assuming the method is the entry point, execute the method)     public void DebugResult()     {         //2. Then execute the method         handler.Result(3, 2 , (a,b)=>{return a+b;});//5. Go back to the caller and execute (a,b)=>{return a+b;} }//8. Exit the caller      method }

class TesHandler 
{     //3. Enter Result      public int Result(int a, int b , CalTestHandler calHandler )     {         //4. Call the delegate method         return calHandler(a, b);//6. Return to the definition end and execute it     }/ /7. Exit definition end method

    //Define delegate
    public delegate int CalTestHandler(int a, int b);

}

/*

委托实现回调：
    通过委托以方法作为参数进行传递
    回调的机制：从调用端 -> 定义端 -> 调用端 -> 定义端 -> 调用端

    调用端 执行方法(方法参数含有委托类型) -> 
    进入到定义方法端口，执行方法中的代码块，执行到委托方法 ->
    回到调用端执行传递的方法参数 ->
    回到定义端 继续执行后面的代码块 ->
    执行完毕 回到调用端

*/


class TestCallBack
{
    TesHandler handler =new TesHandler();
    //1.执行该方法（假设该方法为入口 即执行该方法）
    public void DebugResult()
    {
        //2.进而执行该方法
        handler.Result(3, 2, (a,b)=>{return a+b;});//5.回到调用端 执行(a,b)=>{return a+b;} 
    }//8.退出调用端方法
}


class TesHandler 
{
    //3.进入Result 
    public int Result(int a, int b , CalTestHandler calHandler )
    {
        //4.调用委托方法
        return calHandler(a, b);//6.回到定义端 执行完毕
    }//7.退出定义端方法

    //定义委托
    public delegate int CalTestHandler(int a, int b);

}