Func, Action, Predicate

Func, Action, Predicate

Func<T,...,TResult> represents a method that returns a value, Action<T,...> represents one that returns nothing, and Predicate<T> represents one that takes a T and returns bool. These built-in generic delegate types save you from declaring a custom delegate type for common shapes. They're used extensively throughout LINQ and collection methods.

Note: Func<int, int, int> means "takes two ints, returns an int" — the last type parameter is always the return type.

Example: Func, Action, Predicate

using System;

class Program
{
    static void Main(string[] args)
    {
        Func<int, int, int> add = (a, b) => a + b;
        Action<string> print = msg => Console.WriteLine(msg);
        Predicate<int> isEven = n => n % 2 == 0;

        Console.WriteLine(add(4, 5));
        print("Hello from Action");
        Console.WriteLine(isEven(10));
    }
}