Don Wrote: > You need to call the delegate you've made.
I missed this key point. So to summary: int a=1; int b=2; 1.nested function; 2.int c=(int a,int b){return a+b;}(a,b); 3.int c=(int,int){return a+b;}(a,b); 4.int c=(){return a+b;}(); 5.int c={return a+b;}(); How come the last one is legal? Thank you all for all your help!