C＃-为什么我可以在未实例化的类中使用委托？

Question

I thought that delegate fields are just like other fields and that I cannot use them until the class is instantiated. However:

 class Program
    {

        delegate void lol (int A);
         string myX;

        static void Main(string[] args)
        {
            lol x = ... //works     

            myX //does not exist, 
        }
    }

Answer 1

delegate void lol (int A);

A Delegate is not a field it is a "Nested Type", So you can use it just like any other types.

And refering to myX inside the Main is illegal because myX is instance field. you need to use instance.myX to use it inside a static method( Main() here )

To be more clear, Try the following you'll realize what you're doing wrong

class Program
{
    delegate void lol (int A);
     string myX;
     lol l; 

    static void Main(string[] args)
    {
        l = null; //does not exist
        myX //does not exist, 
    }
}

Answer 2

A delegate instance is an object that refers to one or more target methods.

lol x = ... THIS WILL CREATE DELEGATE INSTANCE

class Program
{

    delegate void lol (int A);
     string myX;

    static void Main(string[] args)
    {
        lol x = ... // THIS WILL CREATE DELEGATE INSTANCE
        x(3) // THIS WILL INVOKE THE DELEGATE

        myX //does not exist, 
    }
}

Another importent delegate Syntaxis I have copied for you from MSDN

    // Original delegate syntax required  
    // initialization with a named method.
    TestDelegate testDelA = new TestDelegate(M);

    // C# 2.0: A delegate can be initialized with 
    // inline code, called an "anonymous method." This
    // method takes a string as an input parameter.
    TestDelegate testDelB = delegate(string s) { Console.WriteLine(s); };

    // C# 3.0. A delegate can be initialized with 
    // a lambda expression. The lambda also takes a string 
    // as an input parameter (x). The type of x is inferred by the compiler.
    TestDelegate testDelC = (x) => { Console.WriteLine(x); };