string型別轉成byte[]： byte[] byteArray = System.Text.Encoding.Default.GetBytes ( str );

反過來，byte[]轉成string：

string str = System.Text.Encoding.Default.GetString ( byteArray );

其它編碼方式的，如System.Text.UTF8Encoding，System.Text.UnicodeEncoding class等；例如：

string型別轉成ASCII byte[]：（"01" 轉成 byte[] = new byte[]{ 0x30, 0x31}）

byte[] byteArray = System.Text.Encoding.ASCII.GetBytes ( str );

ASCII byte[] 轉成string：（byte[] = new byte[]{ 0x30, 0x31} 轉成 "01"）

string str = System.Text.Encoding.ASCII.GetString ( byteArray );

有時候還有這樣一些需求：

byte[] 轉成原16進位制格式的string，例如0xae00cf, 轉換成 "ae00cf"；new byte[]{ 0x30, 0x31}轉成"3031":

      

public static string ToHexString(byte[] bytes) // 0xae00cf => "AE00CF "
        {
            string hexString = string.Empty;
            if (bytes != null)
            {
                StringBuilder strB = new StringBuilder();

                for (int i = 0; i < bytes.Length; i++)
                {
                    strB.Append(bytes[i].ToString("X2"));
                }
                hexString = strB.ToString();
            }
            return hexString;
        }

反過來，16進位制格式的string 轉成byte[]，例如, "ae00cf"轉換成0xae00cf，長度縮減一半；"3031" 轉成new byte[]{ 0x30, 0x31}:       

 public static byte[] GetBytes(string hexString, out int discarded)
        {
            discarded = 0;
            string newString = "";
            char c;
            // remove all none A-F, 0-9, characters
            for (int i = 0; i < hexString.Length; i++)
            {
                c = hexString[i];
                if (IsHexDigit(c))
                    newString += c;
                else
                    discarded++;
            }
            // if odd number of characters, discard last character
            if (newString.Length % 2 != 0)
            {
                discarded++;
                newString = newString.Substring(0, newString.Length - 1);
            }

            int byteLength = newString.Length / 2;
            byte[] bytes = new byte[byteLength];
            string hex;
            int j = 0;
            for (int i = 0; i < bytes.Length; i++)
            {
                hex = new String(new Char[] { newString[j], newString[j + 1] });
                bytes[i] = HexToByte(hex);
                j = j + 2;
            }
            return bytes;
        }