Introduction to C# Multithreading

1. Introduction

In this tutorial, we aim to introduce the concept of multithreading in C#. Multithreading is a powerful feature that allows a program to perform multiple tasks concurrently, leading to better use of resources and improved performance.

By the end of this tutorial, you will understand:

• What threads are and why they are crucial in modern programming.
• How multithreading works in C#.
• Best practices for using multithreading.

Prerequisites: Basic knowledge of C# programming. Familiarity with concepts like loops, functions, and objects will be beneficial.

2. Step-by-Step Guide

A thread represents a separate flow of control within a program in C#. By default, every C# program has at least one thread, known as the main thread. Additional threads can be created to perform separate tasks concurrently.

Using multithreading, you can create more responsive applications and make better use of system resources. However, multithreading can also introduce complexity and potential issues, so it's important to use it wisely.

Creating a Thread

In C#, we can create a thread by creating an instance of the Thread class, which resides in the System.Threading namespace. Here's an example:

using System;
using System.Threading;

class Program
{
    static void Main(string[] args)
    {
        Thread newThread = new Thread(DoWork);
        newThread.Start();
    }

    static void DoWork()
    {
        for (int i = 0; i < 10; i++)
        {
            Console.WriteLine("Thread - Working");
        }
    }
}

In this code, we first import the necessary namespaces. We then define a method named DoWork that will be executed in a new thread. We create a new thread by passing the DoWork method to the Thread constructor. Finally, we call the Start method to start the new thread.

Thread Synchronization

When multiple threads are accessing and modifying shared data, it can lead to inconsistencies. To prevent this, we use thread synchronization techniques such as lock, Monitor, Mutex, etc.

3. Code Examples

Example 1: Creating and Starting a Thread

using System;
using System.Threading;

class Program
{
    static void Main(string[] args)
    {
        Thread newThread = new Thread(DoWork);
        newThread.Start();
    }

    static void DoWork()
    {
        for (int i = 0; i < 10; i++)
        {
            Console.WriteLine("Thread - Working");
        }
    }
}

This will print "Thread - Working" 10 times.

Example 2: Thread Synchronization with lock

using System;
using System.Threading;

class Program
{
    static readonly object _object = new object();

    static void Main(string[] args)
    {
        for (int i = 0; i < 10; i++)
        {
            Thread newThread = new Thread(DoWork);
            newThread.Start();
        }
    }

    static void DoWork()
    {
        lock (_object)
        {
            Console.WriteLine("Thread - Working");
            Thread.Sleep(1000);
        }
    }
}

In this example, we are creating ten threads. lock ensures that only one thread executes the code block at a time.

4. Summary

In this tutorial, we learned about multithreading in C#. We discussed how to create and start threads, and how to synchronize them to avoid inconsistencies.

Next, you could explore more advanced topics like thread pooling, tasks, and parallel programming in C#. Here are some resources to help:

• Microsoft's Documentation on Multithreading
• C# Station's Tutorial on Multithreading

5. Practice Exercises

1. Create a program that creates and starts multiple threads.
2. Modify the above program to synchronize the threads using the lock keyword.
3. Create a program that uses a Mutex for thread synchronization.

Remember, practice is key to mastering any concept. Happy Coding!