CsharpHow-ToBeginner · 3 min read

How to Use Thread Class in C#: Simple Guide with Examples

In C#, use the Thread class to run code on a separate thread by creating a Thread object with a method to execute, then start it with Start(). This allows your program to perform tasks concurrently, improving responsiveness or performance.

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Syntax

The Thread class is used to create and control a thread. You create a new thread by passing a ThreadStart delegate or a lambda expression to the Thread constructor. Then, call Start() to begin execution.

Thread thread = new Thread(MethodName); - creates a new thread that will run MethodName.
thread.Start(); - starts the thread.

csharp

Thread thread = new Thread(MethodName);
thread.Start();

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Example

This example shows how to create a thread that runs a method printing numbers from 1 to 5 while the main thread prints letters. Both run at the same time.

csharp

using System;
using System.Threading;

class Program
{
    static void PrintNumbers()
    {
        for (int i = 1; i <= 5; i++)
        {
            Console.WriteLine($"Number: {i}");
            Thread.Sleep(500); // Pause for half a second
        }
    }

    static void Main()
    {
        Thread thread = new Thread(PrintNumbers);
        thread.Start();

        for (char c = 'A'; c <= 'E'; c++)
        {
            Console.WriteLine($"Letter: {c}");
            Thread.Sleep(700); // Pause for 0.7 seconds
        }

        thread.Join(); // Wait for the thread to finish
        Console.WriteLine("Main thread finished.");
    }
}

Output

Number: 1 Letter: A Number: 2 Letter: B Number: 3 Letter: C Number: 4 Letter: D Number: 5 Letter: E Main thread finished.

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Common Pitfalls

Some common mistakes when using Thread include:

Not calling Start() on the thread, so it never runs.
Accessing shared data without synchronization, causing data corruption.
Not using Join() if you need to wait for the thread to finish before continuing.
Creating threads for very short tasks, which can be inefficient.

Always ensure thread safety and proper thread lifecycle management.

csharp

/* Wrong: Thread created but not started */
Thread thread = new Thread(() => Console.WriteLine("Hello"));
// thread.Start(); // Missing start call

/* Right: Start the thread */
Thread thread2 = new Thread(() => Console.WriteLine("Hello"));
thread2.Start();

Output

Hello

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Quick Reference

Action	Code Example	Description
Create Thread	Thread t = new Thread(Method);	Creates a new thread to run Method.
Start Thread	t.Start();	Begins execution of the thread.
Wait for Thread	t.Join();	Blocks current thread until t finishes.
Sleep Thread	Thread.Sleep(1000);	Pauses current thread for 1 second.

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Key Takeaways

Create a Thread object with a method to run and call Start() to run it.

Use Join() to wait for a thread to finish if needed.

Avoid accessing shared data without synchronization to prevent errors.

Do not forget to call Start(), or the thread will not run.

Use Thread.Sleep() to pause a thread safely.