- If lower layer (DB) wants to callback higher layer (UI)，we can define a delegate in lower layer，then in higher layer we instantiate that delegate with the implementation method in higher layer，for example,
public static MyDelegate MyDel= null;
higher layer：lower.MyDel = DelImpl;
void DelImpl()
{
//implementation
}
- We can use named methods, anonymous methods or lambda expression to instantiate the delegate:
- Named method
delegate void Del();
void DoWork(); // support both instance method and static method
Del d = DoWork; // Is equal to "Del d = new Del(DoWork);", but simpler.
- Anonymous method
delegate void Del();
Del d = delegate() {/*....code block...*/};
delegate int Del(int x);
- Lambda expression (a type of anonymous method)
Del d = (x)=> {return x * x;}
- Multicast delegate: (+: add object to delegate, -:remove object from delegate, execute in order, only can combine the delegate with same type), for example:
delegate void Del();
void Hello();
void World();
Del d1 = Hello;
Del d2 = World;
Del d3 = d1 + d2;
Del d4 = d3 - d2;
d3(); // first call Hello(), then call World();
d4(); // only call Hello();
作者：chuwachen 发表于2013-2-1 15:55:39 原文链接
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