Benefits of Delegate with example

Question

Hi
I know basic idea about delegate but it is difficult to understand exactly where it must be used(scenarios) also the performance issues, when delegates are used and without it. please let me know with the help of simple example as the examples on the net are not that useful. Thanks in advance for your efforts.

Vulpes · Answer

Well as you know delegates are the basis of events anonymous methods and lambda expressions which would be more than enough to justify their existence. However they are still useful on their own in two main scenarios: 1. For passing methods as parameters to other methods. 2. For calling more than one method at a time (multi-casting). Here's a simple example which illustrates both usages: using System; delegate int Mutater (int i); class Test { static int Square(int i) { return i * i; } static int Cube(int i) { return i * i * i; } static int SquareRoot(int i) { return (int)Math.Sqrt(i); } static int CubeRoot(int i) { return (int)Math.Round(Math.Pow(i 1.0/3.0)); } static void Main() { int[] values = {1 2 3 4}; PrintResults(Original values (first set) values); Mutater m = Square; Mutate(values m); PrintResults(Squared values); m += SquareRoot; // now multicast Mutate(values m); PrintResults(Squared then square-rooted values); int[] values2 = {5 6 7 8}; PrintResults(Original values (second set) values2); Mutater m2 = Cube; Mutate(values2 m2); PrintResults(Cubed values2); m2 += CubeRoot; // now multicast Mutate(values2 m2); PrintResults(Cubed then cube-rooted values2); Console.ReadKey(); } static void Mutate(int[] values Mutater m) { foreach(Mutater mm in m.GetInvocationList()) { for(int i = 0; i } } static void PrintResults(string message int[] values) { Console.WriteLine(message); foreach(int value in values) Console.WriteLine({0}  value); Console.WriteLine(); } } The output should be: Original values (first set) 1 2 3 4 Squared 1 4 9 16 Squared then square-rooted 1 4 9 16 Original values (second set) 5 6 7 8 Cubed 125 216 343 512 Cubed then cube-rooted 125 216 343 512 Clearly the use of delegates does have some performance implication compared to calling methods directly. This is because the delegate is a wrapper both for the method and the object (if any) on which it's called and so when you call a method via a delegate there's an extra level of indirection. Also delegates take up memory on the heap and need to be garbage collected when they're no longer needed. However Microsoft have done a lot of work to minimize the impact on both performance and heap usage so unless you're creating thousands of delegates I don't think you need to worry much about either of these in practice.