C #: Wen Zhixin-delegation and events (Delegation)

Introduction: delegation is a type. Its position is the same as that of class, struct, and enum. We can say this: A delegate can be declared in any place where the class can be declared. We often put the delegate and event together for understanding. In fact, this is only an application of the delegate. To understand the nature of delegation, we must investigate the nature of the phenomenon. What is the purpose of delegation?

Symptom:

Public Delegate void mydelegate (); Public Delegate string mydelegate (string name );

From the above two delegate statements, we will find that the delegate seems very similar to the method statement. Indeed, the delegate has a return type and a list of corresponding parameters, which are actually the "return type" and "parameter list" that limit addition (or "Registration"). to the method type in the delegate, that is, only the return type and parameter list (parameter type, number, etc.) that are the same as the delegate can be registered or added in the delegate.

Essence: the essence of delegation is to encapsulate the methods, but there are rules for the methods encapsulated into the delegation. From the perspective of the memory stack, the delegate encapsulation is not a specific method, but the address of the method in the memory heap (a bit like the function pointer in C ++, in fact, I personally understand this ). In addition, the methods added to the delegate are sequential. WhenProgramWhen a delegate is called, it calls the method according to the sequence in the method list. If the return type is specified during the delegate definition, and there are multiple methods in the delegate, after the delegate is called, the returned value is the return value of the last method. The returned values of the previous method are ignored by the program.

Learn new things with a gentle understanding-looking back at the knowledge you 've learned before, maybe new discoveries and gains.