Exit parameter (link) with action <>

Question

I have many methods like this:

  void GetColorSky(out float r, out float g, out float b) void GetColorGround(out float r, out float g, out float b) 

“Like” means that they have the same method header excluding the method name. I also have several colourPicker controls that take values ​​of R, G, B.

I am trying to create a method that takes a method as one of its parameters, for example:

 UpdateColourPicker(ColorPicker cp, CustomMethod cMethod) 

and name it as follows:

 UpdateColourPicker(cpSky, GetColorSky) UpdateColourPicker(cpGround, GetColorGround) 

What is the correct syntax for out and Action together? I looked through this question , but I still failed.

Thanks!

Answer 1

Taking the answer from this related answer, this will work:

 public delegate void GetColorDel(out float r, out float g, out float b); void UpdateColourPicker(ColorPicker cp, GetColorDel cMethod) { } UpdateColourPicker(cpSky, GetColorSky); UpdateColourPicker(cpGround, GetColorGround); 

Unfortunately, as indicated in the answer to your question, Action and Func do not work with out and ref . This is simply because Action and Func are just delegate definitions (quite a few times to offer different overloads) with generics in BCL. Adding ref and out options will quickly cause override compiler errors.

Full sample:

 class Program { public delegate void GetColorDel(out float r, out float g, out float b); static void Main(string[] args) { UpdateColourPicker(null, GetColorSky); UpdateColourPicker(null, GetColorGround); Console.Read(); } static void GetColorSky(out float r, out float g, out float b) { r = g = b = 0f; Console.WriteLine("sky"); } static void GetColorGround(out float r, out float g, out float b) { r = g = b = 0f; Console.WriteLine("ground"); } static void UpdateColourPicker(object cp, GetColorDel cMethod) { float r, g, b; cMethod(out r, out g, out b); } } 

Answer 2

If you want to define a common delegate with out parameters, this should be done as follows:

 delegate void ActionWithOutparameter<T>(out T x); delegate void ActionWithOutparameter<T1, T2>(out T1 x, out T2 y); // ... 

Obviously, the Action and Func delegates in the BCL do not match this signature.