Prevent multiple instances of a given app in NET

Question

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

User · Answer

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  gt 1                  return    That s it

User · Answer

You have to use System Diagnostics Process   Check out  http   www devx com tips Tip 20044

User · Answer

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

User · Answer

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

User · Answer

http   www codeproject com KB cs SingleInstancingWithIpc aspx

User · Answer

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

User · Answer

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    gt                                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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

http   en csharp-online net Application Architecture in Windows Forms 2 0   Single-Instance Detection and Management

User · Answer

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  gt  1                           Application Exit                           return                                                                    catch                       Application Run new Form1

User · Answer

http   en csharp-online net Application Architecture in Windows Forms 2 0   Single-Instance Detection and Management

User · Answer

if  Process GetProcessesByName Process GetCurrentProcess   ProcessName  Length  gt  1      AppLog Write  Application XXXX already running  Only one instance of this application is allowed   AppLog LogMessageType Warn     return

User · Answer

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

User · Answer

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  gt  1                           Application Exit                           return                                                                    catch                       Application Run new Form1

User · Answer

http   en csharp-online net Application Architecture in Windows Forms 2 0   Single-Instance Detection and Management

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

http   www codeproject com KB cs SingleInstancingWithIpc aspx

User · Answer

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

User · Answer

http   www codeproject com KB cs SingleInstancingWithIpc aspx

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

You have to use System Diagnostics Process   Check out  http   www devx com tips Tip 20044

User · Answer

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

User · Answer

http   www codeproject com KB cs SingleInstancingWithIpc aspx

User · Answer

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

User · Answer

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

User · Answer

http   en csharp-online net Application Architecture in Windows Forms 2 0   Single-Instance Detection and Management

User · Answer

if  Process GetProcessesByName Process GetCurrentProcess   ProcessName  Length  gt  1      AppLog Write  Application XXXX already running  Only one instance of this application is allowed   AppLog LogMessageType Warn     return

User · Answer

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    gt                                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

User · Answer

Hanselman has a post on using the WinFormsApplicationBase class from the Microsoft VisualBasic assembly to do this

User · Answer

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

User · Answer

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

User · Answer

if  Process GetProcessesByName Process GetCurrentProcess   ProcessName  Length  gt  1      AppLog Write  Application XXXX already running  Only one instance of this application is allowed   AppLog LogMessageType Warn     return

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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  gt 1                  return    That s it

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

Hanselman has a post on using the WinFormsApplicationBase class from the Microsoft VisualBasic assembly to do this

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

Hanselman has a post on using the WinFormsApplicationBase class from the Microsoft VisualBasic assembly to do this

User · Answer

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

User · Answer

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

User · Answer

You have to use System Diagnostics Process   Check out  http   www devx com tips Tip 20044

User · Answer

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

User · Answer

Hanselman has a post on using the WinFormsApplicationBase class from the Microsoft VisualBasic assembly to do this

User · Answer

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

User · Answer

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

User · Answer

if  Process GetProcessesByName Process GetCurrentProcess   ProcessName  Length  gt  1      AppLog Write  Application XXXX already running  Only one instance of this application is allowed   AppLog LogMessageType Warn     return

User · Answer

You have to use System Diagnostics Process   Check out  http   www devx com tips Tip 20044

User · Answer

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

User · Answer

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

User · Answer

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

[c#] Prevent multiple instances of a given app in .NET?

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