Tutorial: Using Action, Func, and Predicate Delegates in C

1. Introduction

Tutorial's Goal

This tutorial aims to provide a comprehensive guide on using Action, Func, and Predicate Delegates in C#. These delegates represent methods with different signatures and usage that can make your code more flexible and generic.

What You Will Learn

By the end of this tutorial, you will understand the following concepts:
- What are Action, Func, and Predicate delegates
- How to use these delegates in your C# programs

Prerequisites

Before getting started, you should have a basic understanding of C# programming and its syntax.

2. Step-by-Step Guide

Action Delegates:

The Action delegate in C# represents a method that contains a void return type and optionally has parameters.

Example:

// Define an Action delegate
Action<string> display = delegate(string message)
{
    Console.WriteLine(message);
};

// Use the delegate
display("Hello, World!");

Func Delegates:

Func delegate represents a function that can take up to 16 input parameters and returns a value. The last type parameter is always the result.

Example:

// Define a Func delegate
Func<int, int, int> add = delegate(int a, int b)
{
    return a + b;
};

// Use the delegate
int result = add(10, 20);
Console.WriteLine(result); // Outputs 30

Predicate Delegates:

Predicate delegate represents a method that takes one input parameter and returns a boolean value.

Example:

// Define a Predicate delegate
Predicate<string> isUpper = IsUpperCase;

bool result = isUpper("hello");
Console.WriteLine(result); // Outputs False

public static bool IsUpperCase(string str)
{
    return str.Equals(str.ToUpper());
}

3. Code Examples

Let's take a look at some more detailed examples:

Using Action Delegate

Action<int, int> calculate = (a, b) =>
{
    Console.WriteLine($"Sum: {a + b}");
    Console.WriteLine($"Difference: {a - b}");
};

calculate(10, 5); 
// Outputs: 
// Sum: 15
// Difference: 5

Using Func Delegate

Func<int, int, int> multiply = (a, b) => a * b;
int product = multiply(10, 2);
Console.WriteLine($"Product: {product}"); // Outputs: Product: 20

Using Predicate Delegate

Predicate<int> isEven = n => n % 2 == 0;
bool result = isEven(4);
Console.WriteLine($"Is Even: {result}"); // Outputs: Is Even: True

4. Summary

In this tutorial, we covered:

• Action, Func, and Predicate delegates in C#
• How to define and use these delegates
• Examples of these delegates in action

Next, you can explore more about delegates and their use cases in C#. For more information, refer to the Microsoft C# Delegates Documentation.

5. Practice Exercises

1. Write a method using Func delegate that takes two strings and returns their concatenation.
2. Write a method using Predicate delegate that checks if a number is a prime number.
3. Write a method using Action delegate that prints square of a number.

Solutions

Func<string, string, string> concatenate = (a, b) => a + b;
string result = concatenate("Hello, ", "World!");
Console.WriteLine(result); // Outputs: Hello, World!

Predicate<int> isPrime = n =>
{
    if (n <= 1) return false;
    for (int i = 2; i * i <= n; i++)
    {
        if (n % i == 0) return false;
    }
    return true;
};
bool result = isPrime(7);
Console.WriteLine(result); // Outputs: True

Action<int> printSquare = n => Console.WriteLine(n * n);
printSquare(5); // Outputs: 25