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How to ensure single instance application (on multiple virtual desktops)?

I'm writing a C# WinForms application that I need to ensure there's a single instance running at any given time. I thought I had it working using a Mutex.
Here is a link that I found :
How to restrict the application to just one instance.
This worked fine when I'm using a single desktop. However, when there are several virtual desktops open in Windows 10, each of those desktops can host another instance of the application.
Is there a way of limiting a single instance across ALL desktops?

If you look at Remarks section of the docs (see Note block) - you can see, that all you have to do is to prefix your mutex with "Global\". Here is an example for WinForms:
// file: Program.cs
[STAThread]
private static void Main()
{
using (var applicationMutex = new Mutex(initiallyOwned: false, name: #"Global\MyGlobalMutex"))
{
try
{
// check for existing mutex
if (!applicationMutex.WaitOne(0, exitContext: false))
{
MessageBox.Show("This application is already running!", "Already running",
MessageBoxButtons.OK, MessageBoxIcon.Information);
return;
}
}
// catch abandoned mutex (previos process exit unexpectedly / crashed)
catch (AbandonedMutexException exception) { /* TODO: Handle it! There was a disaster */ }
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new MainForm());
}
}

Only allow the newest instance of my application to execute?

I currently have mutex in my app that allows only 1 instance to run. My question is, how do I take this code now, and transform it to close the currently running instance and allow a new one to open?
The problem I am trying to solve: My app takes in args and needs to be reopened often with new params. Currently, without mutex it can open an infinite number of times. I would like only 1 instance with the newest set of params to run.
Thanks,
Kevin
Some Code
bool createdMutex = true;
Mutex mutex = new Mutex(true, "VideoViewerApp", out createdMutex);
if (createdMutex && mutex.WaitOne())
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new frmVideo(args[0], args[1], args[2], args[4], args[5]));
mutex.ReleaseMutex();
}
mutex.close();

The mutex was not meant for interprocess event notification, so there is no way to close another process by using mutexes. What I would recommend would be to do something like what is recommended in this question.
I'll combine the two answers there into something like what I've used:
Process[] processes = Process.GetProcesses();
string thisProcess = Process.GetCurrentProcess().MainModule.FileName;
string thisProcessName = Process.GetCurrentProcess().ProcessName;
foreach (var process in processes)
{
// Compare process name, this will weed out most processes
if (thisProcessName.CompareTo(process.ProcessName) != 0) continue;
// Check the file name of the processes main module
if (thisProcess.CompareTo(process.MainModule.FileName) != 0) continue;
if (Process.GetCurrentProcess().Id == process.Id)
{
// We don't want to commit suicide
continue;
}
// Tell the other instance to die
process.CloseMainWindow();
}

How to avoid race condition when acquiring a mutex?

I am using a named system mutex to synchronise 2 processes. This is how I am currently acquiring a mutex within my application:
using System.Threading;
public static bool AcquireMutex()
{
// Protect against double acquisitions
if (MyMutex != null)
{
throw new ApplicationException("Failed to acquire mutex");
}
try
{
// See if a named system mutex has already been created - if it has,
// wait a short amount of time for its release.
MyMutex = Mutex.OpenExisting(MutexName);
if (!MyMutex.WaitOne(TimeSpan.FromSeconds(2), false))
{
// MyMutex still being held
MyMutex = null;
return false;
}
}
catch
{
// MyMutex doesn't exist so create it
MyMutex = new Mutex(true, MutexName);
}
return true;
}
OpenExisting will throw an exception if the named system mutex with MutexName doesn't exist, allowing my application to create it.
However, there seems to be a race condition here - if OpenExisting throws, there is a small window before the call to new Mutex where the other application may have acquired the mutex.
What is the best way to avoid this race condition and make this code more reliable?
A colleague mentioned that he was using CreateMutex from the Win32 Platform SDK in his code (the other process which needs to be synchronised). This doesn't seem to be natively supported by the .NET Framework, however. So I'm not sure it's the best solution for my code.
Update
Based on the answer from #David Schwartz, here is my new code:
public static bool AcquireMutex()
{
// Protect against double acquisitions
if (MyMutex != null)
{
throw new ApplicationException("Failed to acquire mutex");
}
bool createdNew;
MyMutex = new Mutex(true, MutexName, out createdNew);
if (createdNew)
{
// Mutex was created so ownership is guaranteed; no need to wait on it.
return true;
}
try
{
if (!MyMutex.WaitOne(TimeSpan.FromSeconds(2), false))
{
MyMutex = null;
return false;
}
}
catch (AbandonedMutexException)
{
// Other application was aborted, which led to an abandoned mutex.
// This is fine, as we have still successfully acquired the mutex.
}
return true;
}

There's a constructor specifically designed for this purpose. From the docs:
createdNew
Type: System.Boolean
When this method returns, contains a Boolean that is true if a local mutex was created (that is, if name is null or an empty string) or if the specified named system mutex was created; false if the specified named system mutex already existed. This parameter is passed uninitialized.

Kill some processes by .exe file name

How can I kill some active processes by searching for their .exe filenames in C# .NET or C++?

Quick Answer:
foreach (var process in Process.GetProcessesByName("whatever"))
{
process.Kill();
}
(leave off .exe from process name)

My solution is to use Process.GetProcess() for listing all the processes.
By filtering them to contain the processes I want, I can then run Process.Kill() method to stop them:
var chromeDriverProcesses = Process.GetProcesses().
Where(pr => pr.ProcessName == "chromedriver"); // without '.exe'
foreach (var process in chromeDriverProcesses)
{
process.Kill();
}
Update:
In case if you want to do the same in an asynchronous way (using the C# 8 Async Enumerables), check this out:
const string processName = "chromedriver"; // without '.exe'
await Process.GetProcesses()
.Where(pr => pr.ProcessName == processName)
.ToAsyncEnumerable()
.ForEachAsync(p => p.Kill());
Note: using async methods doesn't always mean code will run faster.
The main benefit is that the foreground thread will be released while operating.

You can use Process.GetProcesses() to get the currently running processes, then Process.Kill() to kill a process.

If you have the process ID (PID) you can kill this process as follow:
Process processToKill = Process.GetProcessById(pid);
processToKill.Kill();

You can Kill a specific instance of MS Word.
foreach (var process in Process.GetProcessesByName("WINWORD"))
{
// Temp is a document which you need to kill.
if (process.MainWindowTitle.Contains("Temp"))
process.Kill();
}

Depending on how many processes there are to kill (e.g. when its hundreds like in my case), foreaching over all of them might take quite a while. (interesting sidenote: while Kill() was usually quite quick in .NET FW 4.8 , somehow in NET 6.0 Windows its a lot slower - seeing multiple Win32Exceptions in the debug/trace until the target process is finally done)
Anyway back to topic:
In case of an app shutdown, where u need to make sure every process is is gone, consider using the TAP library - particulary the Parallel shortcuts, hundreds of processes killed within a glimpse.
Usage example:
var procs = Process.GetProcessByName("mydirtyprocesses");
if (procs.Length == 0) return;
procs.AsParallel().ForAll(process =>
{
try
{
process.Kill();
// No process linked to the process comp (mostly because the process died in
// the short timespan between invoking GetProcess() and the effective
// initialization of the props/fields of the component. -OR- Process has
// already exited (when the exit happened after the process component has
// beenpopulated (difference is, in case 1 you cannot even get the Process
// ID from // the component, in case 2 you see data like Id and get the true
// for HasExited // - so always be prepared for that.
// catch (InvalidOperationException)
{
// Process is gone, no further action required
return;
}
// Ensuring process is gone (otherwise try again or fail or whatever)
if (!process.HasExited)
{
// Handle it
}
}
In this particular scenario just wrap it properly in try/catch , as with such a number of processes the probability for an exception is quite increased

static void Main()
{
string processName = Process.GetCurrentProcess().ProcessName;
int processId = Process.GetCurrentProcess().Id;
Process[] oProcesses = Process.GetProcessesByName(processName);
if (oProcesses.Length > 1)
{
if ((MessageBox.Show("Application is opened!", "",MessageBoxButtons.YesNo) == DialogResult.Yes)) ;
{
foreach (var process in Process.GetProcessesByName(processName))
{
if (process.Id != processId)
{
process.Kill();
}
}
}
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new frmLogin());
}
}

public void EndTask(string taskname)
{
string processName = taskname.Replace(".exe", "");
foreach (Process process in Process.GetProcessesByName(processName))
{
process.Kill();
}
}
//EndTask("notepad");
Summary: no matter if the name contains .exe, the process will end. You don't need to "leave off .exe from process name", It works 100%.

How can I check for a running process per user session?

I have a .NET application that I only allow to run a single process at a time of, however that app is used on Citrix boxes from time to time, and as such, can be run by multiple users on the same machine.
I want to check and make sure that the application is only running once per user session, because right now if user A is running the app, then user B gets the "App already in use" message, and should not.
This is what I have now that checks for the running process:
Process[] p = Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName);
if (p.Length > 1)
{
#if !DEBUG
allowedToOpen &= false;
errorMessage +=
string.Format("{0} is already running.{1}", Constants.AssemblyTitle, Environment.NewLine);
#endif
}

EDIT: Improved the answer according to this cw question ...
You can use a mutex for checking wether the app already runs:
using( var mutex = new Mutex( false, AppGuid ) )
{
try
{
try
{
if( !mutex.WaitOne( 0, false ) )
{
MessageBox.Show( "Another instance is already running." );
return;
}
}
catch( AbandonedMutexException )
{
// Log the fact the mutex was abandoned in another process,
// it will still get aquired
}
Application.Run(new Form1());
}
finally
{
mutex.ReleaseMutex();
}
}
Important is the AppGuid - you could make it depend on the user.
Maybe you like to read this article: the misunderstood mutex

As tanascius already say, you can use the Mutex.
On a server that is running Terminal Services, a named system mutex can have two levels of visibility. If its name begins with the prefix "Global\", the mutex is visible in all terminal server sessions. If its name begins with the prefix "Local\", the mutex is visible only in the terminal server session where it was created.
Source: msdn, Mutex Class

Just stating the obvious - although Mutex is usually considered better solution, you can still solve the single-instance-per-session issue without Mutex - just test the SessionId as well.
private static bool ApplicationIsAlreadyRunning()
{
var currentProcess = Process.GetCurrentProcess();
var processes = Process.GetProcessesByName(currentProcess.ProcessName);
// test if there's another process running in current session.
var intTotalRunningInCurrentSession = processes.Count(prc => prc.SessionId == currentProcess.SessionId);
return intTotalRunningInCurrentSession > 1;
}
Source (no Linq)

If Form1 launches non-background threads, and that Form1 exits, you've got a problem: the mutex is released but the process is still there. Something along the lines below is better IMHO:
static class Program {
private static Mutex mutex;
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main() {
bool createdNew = true;
mutex = new Mutex(true, #"Global\Test", out createdNew);
if (createdNew) {
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
else {
MessageBox.Show(
"Application is already running",
"Error",
MessageBoxButtons.OK,
MessageBoxIcon.Error
);
}
}
}
The mutex won't be released as long as the primary application domain is still up. And that will be around as long as the application is running.