In .NET, what's the best way to prevent multiple instances of an app from running at the same time? And if there's no "best" technique, what are some of the caveats to consider with each solution?
Use Mutex. One of the examples above using GetProcessByName has many caveats. Here is a good article on the subject:
http://odetocode.com/Blogs/scott/archive/2004/08/20/401.aspx
[STAThread]
static void Main()
{
using(Mutex mutex = new Mutex(false, "Global\\" + appGuid))
{
if(!mutex.WaitOne(0, false))
{
MessageBox.Show("Instance already running");
return;
}
Application.Run(new Form1());
}
}
private static string appGuid = "c0a76b5a-12ab-45c5-b9d9-d693faa6e7b9";
if (Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName).Length > 1)
{
AppLog.Write("Application XXXX already running. Only one instance of this application is allowed", AppLog.LogMessageType.Warn);
return;
}
Here is the code you need to ensure that only one instance is running. This is the method of using a named mutex.
public class Program
{
static System.Threading.Mutex singleton = new Mutex(true, "My App Name");
static void Main(string[] args)
{
if (!singleton.WaitOne(TimeSpan.Zero, true))
{
//there is already another instance running!
Application.Exit();
}
}
}
Hanselman has a post on using the WinFormsApplicationBase class from the Microsoft.VisualBasic assembly to do this.
1 - Create a reference in program.cs ->
using System.Diagnostics;
2 - Put into void Main() as the first line of code ->
if (Process.GetProcessesByName(Process.GetCurrentProcess().ProcessName).Length >1)
return;
That's it.
After trying multiple solutions i the question. I ended up using the example for WPF here: http://www.c-sharpcorner.com/UploadFile/f9f215/how-to-restrict-the-application-to-just-one-instance/
public partial class App : Application
{
private static Mutex _mutex = null;
protected override void OnStartup(StartupEventArgs e)
{
const string appName = "MyAppName";
bool createdNew;
_mutex = new Mutex(true, appName, out createdNew);
if (!createdNew)
{
//app is already running! Exiting the application
Application.Current.Shutdown();
}
}
}
In App.xaml:
x:Class="*YourNameSpace*.App"
StartupUri="MainWindow.xaml"
Startup="App_Startup"
It sounds like there are 3 fundamental techniques that have been suggested so far.
Derive from the Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase class and set the IsSingleInstance property to true. (I believe a caveat here is that this won't work with WPF applications, will it?)
Use a named mutex and check if it's already been created.
Get a list of running processes and compare the names of the processes. (This has the caveat of requiring your process name to be unique relative to any other processes running on a given user's machine.)
Any caveats I've missed?
i tried all the solutions here and nothing worked in my C# .net 4.0 project. Hoping to help someone here the solution that worked for me:
As main class variables:
private static string appGuid = "WRITE AN UNIQUE GUID HERE";
private static Mutex mutex;
When you need to check if app is already running:
bool mutexCreated;
mutex = new Mutex(true, "Global\\" + appGuid, out mutexCreated);
if (mutexCreated)
mutex.ReleaseMutex();
if (!mutexCreated)
{
//App is already running, close this!
Environment.Exit(0); //i used this because its a console app
}
I needed to close other istances only with some conditions, this worked well for my purpose
Using Visual Studio 2005 or 2008 when you create a project for an executable, on the properties windows inside the "Application" panel there is a check box named “Make single instance application” that you can activate to convert the application on a single instance application.
Here is a capture of the window I'm talking of:
This is a Visual Studio 2008 windows application project.
http://en.csharp-online.net/Application_Architecture_in_Windows_Forms_2.0—Single-Instance_Detection_and_Management
This is the code for VB.Net
Private Shared Sub Main()
Using mutex As New Mutex(False, appGuid)
If Not mutex.WaitOne(0, False) Then
MessageBox.Show("Instance already running", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error)
Return
End If
Application.Run(New Form1())
End Using
End Sub
This is the code for C#
private static void Main()
{
using (Mutex mutex = new Mutex(false, appGuid)) {
if (!mutex.WaitOne(0, false)) {
MessageBox.Show("Instance already running", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
return;
}
Application.Run(new Form1());
}
}
Use VB.NET!
No: really ;)
using Microsoft.VisualBasic.ApplicationServices;
The WindowsFormsApplicationBase from VB.Net provides you with a "SingleInstace" Property, which determines other Instances and let only one Instance run.
[STAThread]
static void Main() // args are OK here, of course
{
bool ok;
m = new System.Threading.Mutex(true, "YourNameHere", out ok);
if (! ok)
{
MessageBox.Show("Another instance is already running.");
return;
}
Application.Run(new Form1()); // or whatever was there
GC.KeepAlive(m); // important!
}
From: Ensuring a single instance of .NET Application
and: Single Instance Application Mutex
Same answer as #Smink and #Imjustpondering with a twist:
Jon Skeet's FAQ on C# to find out why GC.KeepAlive matters
This article simply explains how you can create a windows application with control on the number of its instances or run only single instance. This is very typical need of a business application. There are already lots of other possible solutions to control this.
https://web.archive.org/web/20090205153420/http://www.openwinforms.com/single_instance_application.html
http://www.codeproject.com/KB/cs/SingleInstancingWithIpc.aspx
You have to use System.Diagnostics.Process.
Check out: http://www.devx.com/tips/Tip/20044
(Note: this is a fun-solution! It works but uses bad GDI+ design to achieve this.)
Put an image in with your app and load it on startup. Hold it until the app exits. The user wont be able to start a 2nd instance. (Of course the mutex solution is much cleaner)
private static Bitmap randomName = new Bitmap("my_image.jpg");
Simply using a StreamWriter, how about this?
System.IO.File.StreamWriter OpenFlag = null; //globally
and
try
{
OpenFlag = new StreamWriter(Path.GetTempPath() + "OpenedIfRunning");
}
catch (System.IO.IOException) //file in use
{
Environment.Exit(0);
}
Normally it's done with a named Mutex (use new Mutex( "your app name", true ) and check the return value), but there's also some support classes in Microsoft.VisualBasic.dll that can do it for you.
This worked for me in pure C#. the try/catch is when possibly a process in the list exits during your loop.
using System.Diagnostics;
....
[STAThread]
static void Main()
{
...
int procCount = 0;
foreach (Process pp in Process.GetProcesses())
{
try
{
if (String.Compare(pp.MainModule.FileName, Application.ExecutablePath, true) == 0)
{
procCount++;
if(procCount > 1) {
Application.Exit();
return;
}
}
}
catch { }
}
Application.Run(new Form1());
}
Be sure to consider security when restricting an application to a single instance:
Full article:
https://blogs.msdn.microsoft.com/oldnewthing/20060620-13/?p=30813
We are using a named mutex with a fixed name in order to detect
whether another copy of the program is running. But that also means an
attacker can create the mutex first, thereby preventing our program
from running at all! How can I prevent this type of denial of service
attack?
...
If the attacker is running in the same security context as your
program is (or would be) running in, then there is nothing you can do.
Whatever "secret handshake" you come up with to determine whether
another copy of your program is running, the attacker can mimic it.
Since it is running in the correct security context, it can do
anything that the "real" program can do.
...
Clearly you can't protect yourself from an attacker running at the
same security privilege, but you can still protect yourself against
unprivileged attackers running at other security privileges.
Try setting a DACL on your mutex, here's the .NET way:
https://msdn.microsoft.com/en-us/library/system.security.accesscontrol.mutexsecurity(v=vs.110).aspx
None of this answers worked for me because I needed this to work under Linux using monodevelop. This works great for me:
Call this method passing it a unique ID
public static void PreventMultipleInstance(string applicationId)
{
// Under Windows this is:
// C:\Users\SomeUser\AppData\Local\Temp\
// Linux this is:
// /tmp/
var temporaryDirectory = Path.GetTempPath();
// Application ID (Make sure this guid is different accross your different applications!
var applicationGuid = applicationId + ".process-lock";
// file that will serve as our lock
var fileFulePath = Path.Combine(temporaryDirectory, applicationGuid);
try
{
// Prevents other processes from reading from or writing to this file
var _InstanceLock = new FileStream(fileFulePath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
_InstanceLock.Lock(0, 0);
MonoApp.Logger.LogToDisk(LogType.Notification, "04ZH-EQP0", "Aquired Lock", fileFulePath);
// todo investigate why we need a reference to file stream. Without this GC releases the lock!
System.Timers.Timer t = new System.Timers.Timer()
{
Interval = 500000,
Enabled = true,
};
t.Elapsed += (a, b) =>
{
try
{
_InstanceLock.Lock(0, 0);
}
catch
{
MonoApp.Logger.Log(LogType.Error, "AOI7-QMCT", "Unable to lock file");
}
};
t.Start();
}
catch
{
// Terminate application because another instance with this ID is running
Environment.Exit(102534);
}
}
Related
My app checks at startup if any other instance of the same is running already, if yes then it will close all other instances. For this I tried using Process.GetProcessByName("AppName") function and store all the process with AppName in processes[] array. Now i want to find the PID of current instance so that i can close all other instances of my app (which obviously have same name but different PIDs). But i am unable to find that even after lot of googling. Also how can i find the PID of an instance of my app which i have created with Process.Start("AppName.exe") function called from inside AppName.exe
OK, given problems with my other solution, see the following
In order to hook in between processes, you need some form of IPC. To use the simplicty of shared handles between EventWaitHandles, you could make each program listen for a cancellation flag.
public static EventWaitHAndle CancellationEvent =
new EventWaitHandle(
false,
EventResetMode.AutoReset,
"MyAppCancel");
private object lockObject = new object();
And later...
Task.Run(() =>
{
while(true)
{
CancellationEvent.WaitOne();
lock(lockObject)
if(!thisIsCalling) // static bool to prevent this program from ending itself
Environment.Exit(0);
}
}
And then call the cancellation like so
lock(lockObject)
{
thisIsCalling = true;
CancellationEvent.Set();
thisIsCalling = false;
}
Why don't you just check equality with your current process?
var processes = Process.GetProcessByName("AppName");
foreach (var p in processes)
{
if (p != Process.GetCurrentProcess())
p.CloseMainWindow();
}
If you're interested in closing other instances of your app, why not do the opposite and prevent multiple instances from opening in the first place? Using EventWaitHandle can do this thusly:
bool created;
var eve = new System.Threading.EventWaitHandle(
false,
EventResetMode.AutoReset,
"MyAppHandle",
out created);
if(!created)
{
eve.Set();
Environment.Exit(-1); // Always use an exit error code if you're expecting to call from the console!
}
The handle parameter, "MyAppHandle" in this case, will be shared across the entire system, thus meaning not only will the out created paramete be false on secondary instaces, but you can use eve.Set() to cause the handle to fire acorss application. Set up a listening thread and this can allow a message loop to display a message when you attempt to open second instance.
Task.Run(() =>
{
while(true)
{
eve.WaitOne();
// Display an error here
}
}
I've seen all the other questions regarding creating a single instance app using WPF and I've chosen to use the Microsoft's approach as described here: https://codereview.stackexchange.com/a/25667
This is working fine, but now I'd like to using Caliburn.Micro on this application and this code does not play well with caliburn.
How can I have a single instance wpf application using caliburn micro?
The requirement are quite simple: .net 4.5 and only one instance of the application per user session
Thanks
I use a named mutex in my main method and show a dialog if the mutex already exists.
Check this stack - WPF Single Instance Best Practices
In case anyone is having the same issue, I want to clarify the steps.
First, you have to change what happens in program entry point. As others mentioned, the Main() function that acts as an entry point to WPF programs is auto-generated (App.g.i.cs); So we have to take control of it somehow. As mentioned in this answer, there are several ways to do so. Personally I prefer the Third Approach:
Include another class in your project that defines the Main method as below:
class Startup
{
[STAThread]
public static void Main()
{
// Your single instance control (shown in below code)
...
}
}
Identify the class whose main you want the application to use as entry point. This can be done via the project properties (right-click on your project >properties. or alt+enter while your project is selected in Solution Explorer). In the Application tab, modify the Startup object properties from the drop down:
Second, you have to decide for a mechanism to know if your program is being run more than once. There are several ways to do that (as the other answers mentioned). The one I prefer is this:
...
// Your single instance control:
bool firstInstance = true;
System.Threading.Mutex mutex = new System.Threading.Mutex(true, "some_unique_name_that_only_your_project_will_use", out firstInstance);
if (firstInstance)
{
// Everything that needs to be done in main class, for example:
YourProject.App app = new YourProject.App();
app.InitializeComponent();
app.Run();
}
else
{
// Your procedure for additional instances of program
MessageBox.Show("Another instance of this application is already running.");
}
These two steps together are one of the easiest ways to achieve your goal, even before Caliburn.Micro takes control of your program.
I had difficulty attempting this in the OnStartup() method.
Basically, you want to create a Main method (see No Main() in WPF? ) and wrap the contents using the mutex (see What is a good pattern for using a Global Mutex in C#?)
Mine looked like this:
class SingleGlobalInstance : IDisposable
{
public bool _hasHandle = false;
Mutex _mutex;
private void InitMutex()
{
string appGuid = "My App Name"; //((GuidAttribute)Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(GuidAttribute), false).GetValue(0)).Value;
string mutexId = string.Format("Global\\{{{0}}}", appGuid);
_mutex = new Mutex(false, mutexId);
var allowEveryoneRule = new MutexAccessRule(new SecurityIdentifier(WellKnownSidType.WorldSid, null), MutexRights.FullControl, AccessControlType.Allow);
var securitySettings = new MutexSecurity();
securitySettings.AddAccessRule(allowEveryoneRule);
_mutex.SetAccessControl(securitySettings);
}
public SingleGlobalInstance(int timeOut)
{
InitMutex();
try
{
if(timeOut < 0)
_hasHandle = _mutex.WaitOne(Timeout.Infinite, false);
else
_hasHandle = _mutex.WaitOne(timeOut, false);
if (_hasHandle == false)
{
MessageBox.Show("Another instance is already running");
System.Windows.Application.Current.Shutdown();
}
}
catch (AbandonedMutexException)
{
_hasHandle = true;
}
}
public void Dispose()
{
if (_mutex != null)
{
if (_hasHandle)
_mutex.ReleaseMutex();
_mutex.Close();
}
}
}
And my App.xaml.cs contained:
[STAThread]
public static void Main()
{
using (new SingleGlobalInstance(1000))
{
var application = new App();
application.InitializeComponent();
application.Run();
}
}
I need to ban an application if it starts from the same folder, but allow it if the same application runs from other folders.
The problem is when application closes it's becomes invisible but still is in the memory because it terminates some internal job.
It's very possible that user will start this application again from the same folder quickly when the old instance still terminates in the memory.
But from the other side it should be possible if this application runs from other folders.
Any clue how to do it in C#?
UPDATES:
1
In fact application writes some logs into the local files in subdirectory and into the local database file as well. So it's very possible that it could be some conflict between 2 instances.
2
Guid appGuid = Guid.Parse("305BACEA-4074-11E1-85E1-066E4854019B");
public MainWindow()
{
InitializeComponent();
using (Mutex mutex = new Mutex(false, #"Global\" + appGuid) )
{
if (!mutex.WaitOne(0, false))
{
// MessageBox.Show("Instance already running");
// Somehow here I have to get the path of the running instance.
// If the path the same as the current instance has I have do ban starting instance.
return;
}
GC.Collect();
}
Thank you all of you!
Finally based on this post I found the solution:
public partial class App : Application
{
private Mutex _instanceMutex = null;
protected override void OnStartup(StartupEventArgs e)
{
string path = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location).Replace("\\", ".");
// check that there is only one instance of the control panel running...
bool createdNew;
_instanceMutex = new Mutex(true, path, out createdNew);
if (!createdNew)
{
_instanceMutex = null;
MessageBox.Show("Instance already running");
Application.Current.Shutdown();
return;
}
base.OnStartup(e);
}
protected override void OnExit(ExitEventArgs e)
{
if (_instanceMutex != null)
_instanceMutex.ReleaseMutex();
base.OnExit(e);
}
}
You could use a lock file to indicate that the program is already running on the folder.
When the program starts, it checks for the file in the directory. If it finds it, it shuts down, if not, it creates one and runs as normal. When the program is done, it should delete the file.
This is of course not fool proof. The file will not be deleted if the program crashes, and a user could delete the file while the program is running, bypassing the initial check.
Okay, so i've created my c# application, created an installer for it and have it working installed on my machine.
The problem is, when the user opens the application exe twice, there will be two instances of the application running. I only ever want one instance of the application to be running at any time, how do I go about doing this?
Thanks for your help,
The common technique for this is to create a named Mutex and check for its presence on application start.
See this or this.
Code from DDJ:
class App : Form
{
Mutex mutex;
App()
{
Text = "Single Instance!";
mutex = new Mutex(false, "SINGLE_INSTANCE_MUTEX");
if (!mutex.WaitOne(0, false))
{
mutex.Close();
mutex = null;
}
}
protected override void Dispose(bool disposing)
{
if (disposing)
mutex.ReleaseMutex();
base.Dispose(disposing);
}
static void Main()
{
App app = new App();
if (app.mutex != null) Application.Run(app);
else MessageBox.Show("Instance already running");
}
}
i solved this problem by this
[STAThread]
static void Main()
{
Process[] result = Process.GetProcessesByName("ApplicationName");
if (result.Length > 1)
{
MessageBox.Show("There is already a instance running.", "Information");
System.Environment.Exit(0);
}
// here normal start
}
it is simple, but i had hardly time to check for better solutions.
With thanks to Messrs. Allen and Powell:
static void Main()
{
using (Mutex mutex = new Mutex(false, #"Global\" + appGuid)) {
if (!mutex.WaitOne(0, false)) {
string processName = GetProcessName();
BringOldInstanceToFront(processName);
}
else {
GC.Collect();
Application.Run(new Voting());
}
}
}
private static void BringOldInstanceToFront(string processName) {
Process[] RunningProcesses = Process.GetProcessesByName(processName);
if (RunningProcesses.Length > 0) {
Process runningProcess = RunningProcesses[0];
if (runningProcess != null) {
IntPtr mainWindowHandle = runningProcess.MainWindowHandle;
NativeMethods.ShowWindowAsync(mainWindowHandle, (int) WindowConstants.ShowWindowConstants.SW_SHOWMINIMIZED);
NativeMethods.ShowWindowAsync(mainWindowHandle, (int) WindowConstants.ShowWindowConstants.SW_RESTORE);
}
}
}
I don't know the environment that you are operating in, but something to keep in mind about 'single-instance applications' is how you define single-instance. If the application can be run on multiple workstations at the same time, using a common datasource, is that an issue? Likewise, what about a terminal-services situation (or a "run as" situation) where more than one user is logged into the same computer, do you want to restrict the application in such a way that only one instance per-user, per-computer? Or are you okay with it simply being one instance per user?
The answer to these might lead you in one direction over another. For example, we have a 'single-instance' application with the scope being a group of computers. Only one user is allowed on within that group of workstations. We managed this by have a table in our shared data-source that tracked currently connected users. This is a maintenance issue as you need to be sure that table is 100% accurate all the time. Handling things like unexpected power outages on the workstation, leaving "bogus" records in that table took some careful handling.
I have a Windows Forms application that allows only one instance to be running at the time. I have implemented Singleton by using Mutex. The Application must be startable from commandline (with or without parameters). Application is started and exited by script. User can not take any action on it.
So, application purpose is simple "indicator" application that will just display some visual and graphical information for the enduser. End user can not do anything with it, just see it. It is windows forms application because then visual and graphical appearance is relatively easy implement (you can get it topmost, borderless, etc.).
To put it simply:
How can I exit the current running application when someone tries to run same application with exit commandline parameter?
bool quit = (args.Length > 0 && args[0] == "quit") ? true : false;
using (Mutex mutex = new Mutex(false, sExeName))
{
if (!mutex.WaitOne(0, true))
{
if (quit)
{
// This is the tricky part?
// How can I get reference to "previous" launced
// Windows Forms application and call it's Exit() method.
}
}
else
{
if (!quit)
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
The .NET framework offers a very good generic solution for this. Check the bottom of this MSDN magazine article. Use the StartupNextInstanceHandler() event handler to pass arbitrary commands to the running instance, like "quit".
Is this not over complicating things ? Rather than closing the existing instance and starting a new one, can you not just re-activate the existing instance? Either way round the code below should give you some ideas on how to go about it...?
Process thisProcess = Process.GetCurrentProcess();
Process[] allProcesses = Process.GetProcessesByName(thisProcess.ProcessName);
Process otherProcess = null;
foreach (Process p in allProcesses )
{
if ((p.Id != thisProcess.Id) && (p.MainModule.FileName == thisProcess.MainModule.FileName))
{
otherProcess = p;
break;
}
}
if (otherProcess != null)
{
//note IntPtr expected by API calls.
IntPtr hWnd = otherProcess.MainWindowHandle;
//restore if minimized
ShowWindow(hWnd ,1);
//bring to the front
SetForegroundWindow (hWnd);
}
else
{
//run your app here
}
There is another question about this here
This is a somewhat quick-and-dirty solution which you would probably want to refine:
[STAThread]
static void Main()
{
var me = Process.GetCurrentProcess();
var otherMe = Process.GetProcessesByName(me.ProcessName).Where(p => p.Id != me.Id).FirstOrDefault();
if (otherMe != null)
{
otherMe.Kill();
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
If an instance of the app is already started, that process is killed; otherwise the app starts normally.
I think the easiest way is the following
see the link
http://codenicely.blogspot.com/2010/04/creating-forms-object.html