Background info
I am writing an integration test that spawns a child process (c# console app). The test is counting some rows in the database after the process is spun up and after the process is closed. The process is closed via process.Kill()
When the process is killed in this manner, it doesn't hit the Stop method within the process. I need to call this stop method to stop threads and remove entries from the database in order for the test to pass.
Original Code
The console app process that I am spawning in my test:
static void Main(string[] args)
{
TaskManager tm = new TaskManagerProcess();
if (Environment.UserInteractive ||
(args.EmptyForNull().Any(a => a.Equals("-RunInteractive", StringComparison.OrdinalIgnoreCase) || a.Equals("/RunInteractive"))))
{
tm.ConsoleStart(args);
Console.WriteLine("Press [Enter] to shut down, any other key to mark");
while (true)
{
ConsoleKeyInfo key = Console.ReadKey(true);
if (key.Key == ConsoleKey.Enter)
break;
Console.WriteLine("========================================================");
Console.Out.Flush();
}
Console.WriteLine("Shutting down...");
tm.ConsoleStop();
}
else
{
ServiceBase.Run(tm);
}
}
}
The test code:
//count before starting child proc
int preCount;
//count after process is spun up
int runningsCount;
//count after stopped
int postCount;
//Get an initial count of the logged in modules before svc host is started
user = ApiMethod.GetLoggedInUsers().Where(x => x.RecId == userRecID).FirstOrDefault();
preCount = user.LoggedInModules.Count;
Process proc = Helper.StartProcess(ConnectionBundle);
//Give process time to spin up leaders and workers
await Task.Delay(TimeSpan.FromSeconds(30));
//Get a count of modules after process is spun up
user = ApiMethod.GetLoggedInUsers().Where(x => x.RecId == userRecID).FirstOrDefault();
runningCount = user.LoggedInModules.Count;
//Write a line terminator to the child svc host process -
//this allows it to shutdown normally
Helper.ProcessInput.WriteLine();
Helper.ProcessInput.Close();
Helper.KillProcess(proc);
await Task.Delay(TimeSpan.FromSeconds(5));
//Get count of logged in modules after process is closed
user = ApiMethod.GetLoggedInUsers().Where(x => x.RecId == userRecID).FirstOrDefault();
postCount = user.LoggedInModules.Count;
Helper is a static class that sets up the process start info(including args) and starts the process. In helper I've redirected the StandardInput and added a property ProcessInput which is set to the StandardInput of the created process.
My goal is to send input of "Enter" from the test to the spawned process so that it will break from the loop and call tm.ConsoleStop()
TaskManagerProcess is a private custom class that controls the process. It does not inherit from System.Diagnostics.Process. As an alternate approach, my test could interact with TaskManagerProcess directly. However, I can't make TaskManagerProcess public and I need to run TaskManagerProcess in its own AppDomain because calling ConsoleStop is disposing objects in the API that I need to finish the test.
Things I've Tried
[DllImport("Kernel32")]
private static extern bool SetConsoleCtrlHandler(CloseProcDelgate handler, bool add);
I tried adding a call to Kernel32.SetConsoleCtrlHandler (and the necessary delegate) to call ConsoleStop when the process is exited. This doesn't seem to work when the process is killed via process.Kill()
With the original process code, I noticed an exception when I wrote to the StandardInput. The exception message told me to use Console.Read instead of Console.ReadKey(). This actually works intermittently! I can sometimes get a breakpoint on int cKey = Console.Read() (with debugger attached to child process) but other times it doesn't hit the breakpoint.
while (true)
{
//Changing this to Console.Read instead of Console.ReadKey
//Allows us to send redirected input to process?
int cKey = Console.Read();
if ((ConsoleKey)cKey == ConsoleKey.Enter)
break;
Console.WriteLine("========================================================");
Console.Out.Flush();
}
Finally, I tried interacting with TaskManagerProcess directly. I made the private class internal, and marked the internals visible to my test assembly. I cannot make the class public.
When I go this route, calling tm.ConsoleStop() blows away some objects in my API so I can't check the count after this method is called. For this reason, I thought I would create a new AppDomain and call AppDomain.CreateInstanceAndUnwrap() on the TaskManagerProcess class. However, I get an exception here, I believe its due to the the fact that the class is internal.
I am really stuck at this point! Any help is appreciated and thanks for taking the time to read this!
Edit
I created a demo project here
that shows what I am trying to do and has both approaches in the Test method.
Initially I thought I couldn't call AppDomain.CreateInstanceAndUnwrap() because the TaskManagerProcess class was internal. However, after playing with my demo project, I think I just can't load the assembly.
I'm guessing here, but I believe your TaskManagerProcess is a service application. If it is not, please ignore this. If it is, be advised of including details like this in your question. Debugging service applications can be complicated, believe me, I've been there. But before proceed, more advise.
Test the methods in your modules, no whole running programs, as Michael Randall just said.
Unless absolutely necessary, don't do tests against a database. Mock whatever you need to test your code.
You should go back to your alternate approach of interact with TaskManagerProcess directly. From the code of your console app, the only working method I see called is tm.ConsoleStart(args), the rest inside the loop is console writing and reading. So you can't change the acces level of that class, again, I've been there. What I have done in the past to overcome this is to use conditional compilation to create a kind of public facade in my private or internal modules.
Suppose you have:
internal class TaskManagerContainer
{
private class TaskManagerProcess
{
internal void Start()
{
// stuff
}
private void DoSomething(int arg)
{
// more stuff
}
}
}
Change it like this:
#define TEST
// Symbol TEST can also be defined using the GUI of your IDE or compiler /define option
internal class TaskManagerContainer
{
//
#if TEST
public class TaskManagerProcess
#else
private class TaskManagerProcess
#endif
{
internal void Start()
{
// stuff
}
private void DoSomething(int arg)
{
// more stuff
}
#region Methods Facade for Testing
#if TEST
public void Start_Test()
{
Start();
}
private void DoSomething_Test(int arg)
{
DoSomething(arg);
}
#endif
#endregion
}
}
I really hope it will help you making the methods visible to the test assembly and it won't blow objects in you API.
I think I got it with a brute force approach.
while (!testProcess.HasExited)
{
testProcess.StandardInput.WriteLine();
}
Thanks everyone for the input!
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 have a C# Window Service that runs a batch file (.bat) which in turn, executes a java app. The service runs the .bat file (cmd.exe) with no problem. However, when I try to stop the window service, the cmd.exe process does not die. A new cmd process is stacked if I start the service again.
How do I kill the running cmd.exe process?
Code:
private const string BATCH_FILE_PATH_APPKEY = "Service_Batch_File_Path";
private const string BATCH_FILE_DEFAULT = "Service.bat";
private static Process _proc;
private static bool _hasStarted = false;
public AService()
{
InitializeComponent();
_proc = new Process();
}
protected override void OnStart(string[] args)
{
try
{
string appDirectory = System.Windows.Forms.Application.ExecutablePath;
appDirectory = appDirectory.Substring(0, appDirectory.LastIndexOf("\\"));
string workingDirectory = appDirectory;
string batchFilePath = string.Empty;
batchFilePath = workingDirectory + "Service.bat";
// Make sure it exists
_proc.StartInfo = new ProcessStartInfo(batchFilePath);
_proc.StartInfo.CreateNoWindow = true;
_proc.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
_proc.Start();
_hasStarted = true;
}
catch (System.Exception ex)
{
eventLog1.WriteEntry(ex.ToString() + "\n\nStack Trace:\n" + ex.StackTrace);
OnStop();
}
}
protected override void OnStop()
{
if (_hasStarted)
_proc.CloseMainWindow();
//_proc.Close();
}
TIA,
Alex.
_proc.Kill();
See the details in MSDN: Process.Kill Method
You may find the following link very useful: Process.Close() is not terminating created process,c#
_proc.Kill () will work.... but it will orphan your java app. I have done something similar where a third process was started. You will also need to know which java process to kill. To do this, you can use the ParentProcess Performance Counter.
Here are some details on using the ParentProcess performance counter.
Also, version of Windows do you plan to deploy this on? WindowsServer2008 seems to have a cmd.exe and a conhost.exe. That may pose a problem for you (again one that can probably be resolved by knowing the parent process.
Have you tried _proc.Kill() in your service's closedown processing? This is async and you should then call WaitForExit to give it a decent chance to go away. Log any failures or exceptions in this logic for investigation.
You should also (for cleanliness) reinstate the _proc.Close() after calling WaitForExit(), to ensure Dispose() gets called properly for the Process. I know your service is about to exit, but this is a good habit and means you are less likely to leak if you decide to manage the child Process more dynamically in future.
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.
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);
}
}