C# Single WinApp instance

using System.Threading;
static void Main()
{
  bool isFirstInstance;
  Mutex mutex = 
     new Mutex(true, "Global\\" + “App_Name_Here”, out isFirstInstance);

  if(isFirstInstance)
    Application.Run(new YourAppMainClass());
  else
    MessageBox.Show("There is already an instance running.",
        "Warning",
        MessageBoxButtons.OK, MessageBoxIcon.Exclamation,
        MessageBoxDefaultButton.Buttonx);
}

using System.Diagnostics;
public void WriteEventLog(string appName, string logDetail)
{
 if (!System.Diagnostics.EventLog.SourceExists(appName))
  System.Diagnostics.EventLog.CreateEventSource(appName,"Application");

  EventLog EventLog1 = new EventLog();
  EventLog1.Source = appName;
  EventLog1.WriteEntry (logDetail, EventLogEntryType.Error);
}