С ASCII в UTF-8

string s = Encoding.UTF8.GetString(Encoding.ASCII.GetBytes(String_in_ASCII));

using System;
using System.IO;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
            FileStream fin = File.Open("C:\\in.txt", FileMode.OpenOrCreate);
            FileStream fout = File.Create("C:\\out.txt");
            Int32 len = (Int32)fin.Length;
            byte[] in_bytes = new byte[len];
            fin.Read(in_bytes, 0, len);
 
            Encoding in_code = Encoding.GetEncoding(866);
            Encoding out_code = Encoding.UTF8;
 
            byte[] out_bytes = Encoding.Convert(in_code, out_code, in_bytes, 0, len);
            fout.Write(out_bytes, 0, out_bytes.Length);
            fin.Close();
            fout.Close();
        }
    }
}

Encoding in_code = Encoding.GetEncoding(866);

Encoding in_code = Encoding.ASCII;

out_code.GetString(out_bytes);

Int32 len = (Int32)playername.Length;
  byte[] in_bytes = new byte[len];
            Encoding in_code = Encoding.GetEncoding(866);
            Encoding out_code = Encoding.UTF8;
 
            byte[] out_bytes = Encoding.Convert(in_code, out_code, in_bytes, 0, len);
            string sk = out_code.GetString(out_bytes);
            listBox1.Items.Add("Player Name: " + sk);

string sk = Encoding.ASCII.GetString(in_bytes, 0, len);