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In some scenarios, you may wish to ensure that a user can run only one instance of your application at a time. Besides ensuring that only a single instance of your application is running, you may also want to bring the instance already running to the front and restore it, if it is minimized.

First, to ensure that only one instance of your application is running at a time,博彩, the best method I've found is to create a mutex that is held by the operating system (thanks to ). This will put a request to the operating system that a mutex be created if one does not already exist. Only one mutex can ever be created at a time,六合彩现场开奖, so if you request a new one and it cannot be created, you can safely assume that your application is already running.

using System.Threading
usingSystem.Runtime.InteropServices;

public class Form1 : Form
{
[STAThread]
static void Main()
{
bool createdNew;

Mutex m = new Mutex(true, "YourAppName",足球投注网, out createdNew);

if (! createdNew)
{
// app is already running...
MessageBox.Show("Only one instance of this application is allowed at a time.");
return;
}

Application.Run(new Form1());

// keep the mutex reference alive until the normal termination of the program
GC.KeepAlive(m);
}
}

The above code will work for the vast majority of your needs. It will also run under scenarios where your code is executing with less than FullTrust permissions (see Code Access Security in MSDN for further information).

If your application can run with Full Trust permissions, we can take this a step further and find the window of the application instnace already running and bring it to the front for the user:

public class Form1 : Form
{
[STAThread]
static void Main()
{
bool createdNew;

System.Threading.Mutex m = new System.Threading.Mutex(true, "YourAppName", out createdNew);

if (! createdNew)
{
// see if we can find the other app and Bring it to front
IntPtr hWnd = FindWindow("WindowsForms10.Window.8.app3", "YourAppName");

return;
}

Application.Run(new Form1());

// keep the mutex reference alive until the normal termination of the program
GC.KeepAlive(m);
}

As you can see,六合彩即时开奖, with minimal effort, you can easily add a polished touch to your application. This might even help you avoid some extra legwork in ensuring that there are no issues with running multiple instances of your app at the same time that you might have to address.

For more information about the Platform Invoke mechanisms to call Win32 API functions, I recommend that you check out by John Mueller and Charles Petzold's seminal classic .

Until Longhorn comes out and more of the Windows platform becomes managed, platform invokes and interop will remain a key technology to understand and use to your advantage to fill the gaps left by the Windows Forms framework.

UPDATE:
Visual Studio .NET 2005 (aka. “Whidbey”) will let you specify Single Instance behavior for Visual Basic .NET projects through the Project Properties page. Curious as to why this option is available for VB projects and not for C# projects, as this seems to instruct the runtime or some framework library not to load more than one instance.