Mutex means mutual
exclusion. Mutex is class in .NET framework. It is thread synchronization
process. Mutex is used to prevent the execution of a shared resource by
multiple threads. It allows only one single thread to enter to execute a
particular task. It
is used in single process or multiple processes. It can also be used for inter
process synchronization. Monitor/Lock prevents shared resource from internal
threads, but Mutex prevent from both internal as well as external threads. In
another way we can say, mutex provide thread safety against internal/external
threads.
Example: Multiple threads are writing to file
in this example.
I have synchronization multiple thread using
mutex. Only one thread is accessing shared
resource (file
here) at a time.
using System;
using System.Threading;
using System.IO;
class ConsoleApplication1
{
static void Main(string[] args)
{
for (int i = 0; i < 5; i++)
{
Thread thread = new Thread(new ThreadStart(Go));
thread.Name = String.Concat("Thread ", i);
thread.Start();
}
Console.ReadLine();
}
static void Go()
{
Thread.Sleep(500);
WriteFile();
}
static Mutex mutex = new Mutex();
static void WriteFile()
{
mutex.WaitOne();
String ThreadName = Thread.CurrentThread.Name;
Console.WriteLine("{0} using
resource", ThreadName);
try
{
using (StreamWriter sw = new StreamWriter("C:\\abc.txt", true))
{
sw.WriteLine(ThreadName);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
Console.WriteLine("{0}
releasing resource", ThreadName);
mutex.ReleaseMutex();
}
Handling single
Instance of Application:
namespace ConsoleApplication1
{
class SingleInstance
{
static void Main(string[] args)
{
String appGUID=”5a913d2e-1d4b-492c-a408-df315ca3de93”;
bool ok;
Mutex mutex = new System.Threading.Mutex(true, appGUID, out ok);
if (!ok)
{
Console.WriteLine("Another
instance is already running.");
}
else
{
Console.WriteLine("Single
instance is running.");
}
Console.ReadLine();
}
}
}
When application will be launched first time, you can see
below message.
When application is launched more than 1 times then you will
see below message.
Note:
1. The name of the mutex should be a unique either assembly name or GUID.
2. Mutex
hits performance, so it should be used when synchronization across
process boundaries is required.
process boundaries is required.
3. A
mutex can also be passed across application domain boundaries.
