How to avoid Unhandled exception of type 'System.IO.IOException' error in mscorlib.dll?

Question

Programming

Hello, sometimes this error occurs:
Unhandled exception of type "System.IO.IOException" in mscorlib.dll

The code itself:

using System;
using System.IO;
 
namespace TurboBotNew
{
    public static class Log
    {
        static string s_logFile = System.IO.Directory.GetCurrentDirectory() + "\\log.txt";
        static int i_lastLog = 0;
 
        public static void Write(string message)
        {
            string TimeNow = DateTime.Now.ToString("HH:mm:ss");
            message = "[" + TimeNow + "] " + message + "\n";
            File.AppendAllText(s_logFile, message);
 
        }
 
        public static void Close()
        {
            if (System.IO.File.Exists(s_logFile))
                System.IO.File.Delete(s_logFile);
        }
 
        public static string Read(string s_log)
        {
            if (!System.IO.File.Exists(s_logFile))
                Write("Создание лога");
            var mass = System.IO.File.ReadAllLines(s_logFile);
            string s_message = "";
            for (int i = mass.Length - 1; i > i_lastLog; i--)
            {
                s_message = mass[i] + Environment.NewLine + s_message;
            }
            i_lastLog = mass.Length - 1;
 
            return s_log + s_message;
        }
    }
}

How to avoid this error in this code?

Answer 1

The error occurs because you are trying to open the log file from multiple threads at the same time. Or you just opened it in a text editor at the same time.
PS
Tip number 1: discover NLog
Tip number 2: never do this in a loop

s_message = mass[i] + Environment.NewLine + s_message;

- for such things there is StringBuilder which works faster.
Tip number 3: Better yet, instead of such loops, use a convenient method

s_message  = string.Join(Environment.NewLine, mass)

Tip #4: Better yet, use File.ReadAllText instead of File.ReadAllLines in these cases.

Answer 2

Use StreamWriter to write.
Opened once at the first attempt to write and closed before the end of the program.