How to make a callback call in c #?

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    What is callback in your understanding? What call syntax do you want? And what semantics? How many subscribers, how many call sources? Describe your task in more detail. - VladD
  • Well transfer the subroutine as a parameter to another subroutine. For example in C ++: void do_action (int & x, void (* f) (int &)) {f (x); } in the main program: int i = 5; do_action (i, twice); where twice is a function that doubles the number of how to implement such a mechanism in C #? - rekrut

2 answers 2

It's simple:

C ++:

void do_action(int &x, void(*f)(int &)) { f(x); } int i = 5; do_action(i, twice); void twice(int &x) { x = 2 * x; }

C #:

 public delegate F(ref int x); // как бы typedef void DoAction(ref int x, F f) { f(ref x); } void makeDouble(ref int x) { x = 2 * x; } int i = 5; DoAction(ref i, makeDouble);

Note that makeDouble can be, in contrast to C ++, a non-static (!) Method.

For normal cases when your callback does not accept out / ref arguments, there are delegates that are prepared, and almost always use them:

 // Func<int, int> -- функция, принимающая int и возвращающая тоже int int Apply(int x, Func<int, int> f) { return f(x); } int getDouble(int x) { return 2 * x; } int i = 5; i = Apply(i, getDouble);

Or it can be easier with lambdas:

 int i = 5; i = Apply(i, x => 2 * x);

    Event?

    I could be wrong, but I did something like this:

     public class ArtDMXEventArgs : EventArgs { public IPAddress Sender; public uint Universe; public byte[] Data; } public delegate void ArtDMXHandler(object sender, ArtDMXEventArgs e); class ArtNetNode { public event ArtDMXHandler onArtDMX; // ... private void FireOnArtDMX(IPAddress Sender, uint Universe, byte[] Data) { if (onArtDMX == null) return; ArtDMXEventArgs e = new ArtDMXEventArgs(); e.Sender = Sender; e.Data = Data; e.Universe = Universe; onArtDMX(this, e); } // ... }

    Client Code:

     { // Добавление обработчика Node.onArtDMX += new ArtDMXHandler(onArtDmx); } private void onArtDmx(object Sender, ArtDMXEventArgs e) { // Обработчик, вызывается по приходу пакета }

    All callbacks, as far as I have met, are made according to such mechanics.