C# Delegate use with Generic Method to return Task<T>

Question

I' m missing something here. I 'll be as clear as I can be.

let's say I have this method :

 public Task<CustomClass> TestMethod(string one, string two, int three) { throw new NotImplementedException(); }

and I want to create a generic method that takes methods like these (through a delegate) and does something.

so let's say that I have this class with a delegate and a generic method:

public static class SomeClass { public delegate T CallbackMethodDelegate<T>(params object[] args); public static void InvokeMethod<T>(CallbackMethodDelegate<Task<T>> method, params object[] args) where T: class { method.Invoke(args); } }

my understanding says that T can be a class, so I should be able to do this somewhere in the code :

 SomeClass.InvokeMethod<CustomClass>(TestMethod, "one", "two", 3);

But I get compile error

CS1503:Argument 1: cannot convert from 'method group' to 'SomeClass.CallBackMethodDelegate<Task<CustomClass>>'

I thought it might be an async thing but even if I change the delegate to void I get the same error. Any ideas what I'm missing? Seems like I'm misunderstanding something important about delegates or generics here. Thank you all in advance.

CS1503:Argument 1: cannot convert from 'method group' to 'SomeClass.CallBackMethodDelegate<Task<CustomClass>>' — Timos Valais
– Timos Valais, Commented May 25, 2022 at 9:11
TestMethod doesn't take a single parameter of object[] so you can't use it like that. — DavidG
– DavidG, Commented May 25, 2022 at 9:12
@DavidG you 're right, completely misunderstood the params keyword. — Timos Valais
– Timos Valais, Commented May 25, 2022 at 9:17

Rafal · Accepted Answer · 2022-05-25 09:52:19Z

as the error suggests your method is not compatible with the delegate. The delegate requires object[] as a parameter your method has 3 explicit parameters string,string,int this is not compatible.

what you can do if you really need this is you can create a set of invoke methods that cover wide range of methods:

void InvokeMethod<TResult>(Func<Task<TResult>> method, TParam1 param1) void InvokeMethod<TParam1, TResult>(Func<TParam1,Task<TResult>> method, TParam1 param1) void InvokeMethod<TParam1,TParam2, TResult>(Func<TParam1, TParam2 ,Task<TResult>> method, TParam1 param1, TParam2 param2)

and so on as many parameters you need to have.

you can reduce those methods to single implementation that is not type safe but not accessible directly

void InvokeMethodImpl(Delegate method, params object[] args) => method.DynamicInvoke(args);

so all generic methods would just call this method:

 void InvokeMethod<TParam1, TResult>(Func<TParam1,Task<TResult>> method, TParam1 param1) => InvokeMethodImpl(method, param1);

That's really smart. That is exactly what I was looking for, thank you, I was stuck!

Collectives™ on Stack Overflow

C# Delegate use with Generic Method to return Task<T>

1 Answer 1

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Related