Do you prevent users from running two instances of your application?

<introEmbed body={<> In some cases, running two instances of an application at the same time may cause unexpected result. See this issue is solved via the code below on [SSW Exchange Reporter](https://www.ssw.com.au/archive/exchange-reporter/default.html): </>} />

try
{
 Process current = Process.GetCurrentProcess();
 Process[] processes = Process.GetProcessesByName( current.ProcessName);

 if ( processes.Length>1 )
 {
  DialogResult userOption = MessageBox.Show(Application.ProductName + " is already running on this machine. " + Environment.NewLine+Environment.NewLine +   "Please click: "+Environment.NewLine+
      " - 'Try again' to exit the other instance and try again, or "+Environment.NewLine+
      " - 'Cancel' to exit now."+Environment.NewLine,
      Application.ProductName+" "+(new Version(Application.ProductVersion)).ToString(2),

  MessageBoxButtons.RetryCancel, MessageBoxIcon.Warning);
  switch(userOption)
  {
   case DialogResult.Cancel: return;

   case DialogResult.Retry:
   foreach(Process currProcess in processes)
   {
    if ( currProcess.Id != current.Id)
    {
     currProcess.Kill();
    }
   }
   break;
  }
 }
}
catch (Exception ex)
{
 TracingHelper.Trace(null, Loggers.WindowsUILogger, TracingLevels.DEBUG, "Cannot get process information, Excpetion occured.", ex) ;

 DialogResult result = MessageBox.Show("Exchange Reporter cannot detect process information. This may be caused by disabled 'Performance Counter' on your machine. "+Environment.NewLine+
 "In such case, Exchange Reporter cannot ensure there is only one instance running. "+
 Environment.NewLine+
 "You may continue to run Exchange Reporter, however, please make sure you have only one instance of Exchange Reporter running. "+
 Environment.NewLine+
 "Multiple instances will cause unexpected behaviour. "+
 Environment.NewLine+Environment.NewLine+
 "Please click 'OK' to continue, or click 'Cancel' to quit."
 , Application.ProductName+" "+(new Version(Application.ProductVersion)).ToString(2),
 MessageBoxButtons.OKCancel,
 MessageBoxIcon.Warning);

 if ( result == DialogResult.Cancel)
 {
  return;
 }
}

Code: Avoid running two instances of an application