namespace Stream;
using System.IO;

public class Stream
{
    public static bool ExistFile(string path)
    {
        return File.Exists(path);
    }

    public static void MyReplace(string path, char toReplace, char replace)
    {
        string preResult = String.Empty;
        string result = String.Empty;
        try
        {
            using (StreamReader sr = new StreamReader(path))
            {
                preResult = sr.ReadToEnd();
            }

            foreach (var chara in preResult)
            {
                if (chara == toReplace)
                {
                    result += replace;
                }
                else
                {
                    result += chara;
                }
            }

            using (StreamWriter sw = new StreamWriter(path))
            {
                sw.WriteLine(result);
            }
        }
        catch (Exception)
        {
            throw new ArgumentException("Error");
        }
    }
}