byte [] byteArray = System.Text.Encoding.Default.GetBytes ( str ); 反过来，byte[]转成string：
string str = System.Text.Encoding.Default.GetString ( byteArray ); 其它编码方式的，如System.Text.UTF8Encoding，System.Text.UnicodeEncoding class等；例如：
string类型转成ASCII byte[]：（"01" 转成 byte[] = new byte[]{ 0x30, 0x31}）
byte [] byteArray = System.Text.Encoding.ASCII.GetBytes ( str ); ASCII byte[] 转成string：（byte[] = new byte[]{ 0x30, 0x31} 转成 "01"）
string str = System.Text.Encoding.ASCII.GetString ( byteArray );
有时候还有这样一些需求：
byte[] 转成原16进制格式的string，例如0xae00cf, 转换成 "ae00cf"；new byte[]{ 0x30, 0x31}转成"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;
} 反过来，16进制格式的string 转成byte[]，例如, "ae00cf"转换成0xae00cf，长度缩减一半；"3031" 转成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; }