带参数和 void 返回的 Func 类型

Question

I wanted to know why this doesn't work ? The compiler says that void cannot be used with Func type. In that case what are my options

  Func<int,void> func1 =  (x) => { Console.WriteLine("Hello World"); };

Answer 1

Func<T, TResult> delegate has one parameter and returns a value of the type specified by TResult , you can't use void , because it specifies that method doesn't return any value and can't be used as type argument.

You can use Action<T> delegate in your example, it has a single parameter and doesn't return a value

Action<int> action = (x) => { Console.WriteLine("Hello World"); };

Since x parameter isn't used, you can just use parameterless Action delegate

Action action = delegate { Console.WriteLine("Hello World"); };

Answer 2

您正在寻找Action<int>

Answer 3

You can declare an Action , but the problem can be overcome by returning for example a null object.

Func<int,object> func1 =  (x) => { Console.WriteLine("Hello World"); return null;};
func1(2);