Check out example codes for "detect console close C#". It will help you in understanding the concepts better.

Code Example 1

using System;
using System.Runtime.InteropServices; // modules needed

namespace grepper
{
 	
  class Program
  {
    public static WebClient internet = new WebClient();
    public static bool wasCleared = false;
    [DllImport("Kernel32")]
    private static extern bool SetConsoleCtrlHandler(SetConsoleCtrlEventHandler handler, bool add);

    private delegate bool SetConsoleCtrlEventHandler(CtrlType sig);
    
    private enum CtrlType
    {
        CTRL_C_EVENT = 0,
        CTRL_BREAK_EVENT = 1,
        CTRL_CLOSE_EVENT = 2,
        CTRL_LOGOFF_EVENT = 5,
        CTRL_SHUTDOWN_EVENT = 6
    }
    
    static void Main(string[] args)
    {
        SetConsoleCtrlHandler(Handler, true); // Register the handle 
        while (true)
        {
            Thread.Sleep(50);
        }
    }
    
    private static bool Handler(CtrlType signal)
    {
        switch (signal)
        {
            case CtrlType.CTRL_BREAK_EVENT:
            case CtrlType.CTRL_C_EVENT:
            case CtrlType.CTRL_LOGOFF_EVENT:
            case CtrlType.CTRL_SHUTDOWN_EVENT:
            case CtrlType.CTRL_CLOSE_EVENT:
                
                // CODE HERE WHEN CLOSED
            
            
                Environment.Exit(0);
                return false;

            default:
                return false;
        }
    }
    
  }
  
}

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