What are threads (multi-threading) in C# ?

Threads are the independent units of execution and can run simultaneously with other threads. Threads helps in achieving parallel execution in C#, which is also called multithreading.

A C# program typically starts with a single thread create automatically by CLR (Common Language Runtime) and operating system. If needed, additional threads has to be created manually through code.

An example of multithreaded application is Microsoft Word (well known to all of us). When you are typing in Microsoft word, an another thread is running in background which performs spell check and highlights the misspelled words.

Threads are available in System.Threading namespace.

Following code snippet shows simple example of thread or multi thread environment in C#.

using System;
using System.Threading;

namespace ThreadSample
{
  class Program
  {
    static void Main(string[] args)
    {
      Thread t = new Thread(DoWork); // create a new thread
      t.Start(); // start new thread
      // Simultaneously, do work on the main thread.
      for (int i = 0; i < 100; i++)
        Console.Write("threaded ");
      Console.ReadKey();
    }
    static void DoWork()
    {
      for (int i = 0; i < 100; i++) 
        Console.Write("minds ");
    }
  }
}

Here is the output of the above program, you can see threaded and minds written simultaneously on the console.