/// <summary> 
/// 字符串转16进制字节数组 
/// </summary> 
/// <param name="hexString"></param> 
/// <returns></returns> 
private static byte[] strToToHexByte(string hexString) 
{ 
hexString = hexString.Replace(" ", ""); 
if ((hexString.Length % 2) != 0) 
hexString += " "; 
byte[] returnBytes = new byte[hexString.Length / 2]; 
for (int i = 0; i < returnBytes.Length; i++) 
returnBytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16); 
return returnBytes; 
} 
字节数组转16进制字符串 
/// <summary> 
/// 字节数组转16进制字符串 
/// </summary> 
/// <param name="bytes"></param> 
/// <returns></returns> 
public static string byteToHexStr(byte[] bytes) 
{ 
string returnStr = ""; 
if (bytes != null) 
{ 
for (int i = 0; i < bytes.Length; i++) 
{ 
returnStr += bytes[i].ToString("X2"); 
} 
} 
return returnStr; 
} 
从汉字转换到16进制 
/// <summary> 
/// 从汉字转换到16进制 
/// </summary> 
/// <param name="s"></param> 
/// <param name="charset">编码,如"utf-8","gb2312"</param> 
/// <param name="fenge">是否每字符用逗号分隔</param> 
/// <returns></returns> 
public static string ToHex(string s, string charset, bool fenge) 
{ 
if ((s.Length % 2) != 0) 
{ 
s += " ";//空格 
//throw new ArgumentException("s is not valid chinese string!"); 
} 
System.Text.Encoding chs = System.Text.Encoding.GetEncoding(charset); 
byte[] bytes = chs.GetBytes(s); 
string str = ""; 
for (int i = 0; i < bytes.Length; i++) 
{ 
str += string.Format("{0:X}", bytes[i]); 
if (fenge && (i != bytes.Length - 1)) 
{ 
str += string.Format("{0}", ","); 
} 
} 
return str.ToLower(); 
} 
16进制转换成汉字 
///<summary> 
/// 从16进制转换成汉字 
/// </summary> 
/// <param name="hex"></param> 
/// <param name="charset">编码,如"utf-8","gb2312"</param> 
/// <returns></returns> 
public static string UnHex(string hex, string charset) 
{ 
if (hex == null) 
throw new ArgumentNullException("hex"); 
hex = hex.Replace(",", ""); 
hex = hex.Replace("\n", ""); 
hex = hex.Replace("\\", ""); 
hex = hex.Replace(" ", ""); 
if (hex.Length % 2 != 0) 
{ 
hex += "20";//空格 
} 
// 需要将 hex 转换成 byte 数组。 
byte[] bytes = new byte[hex.Length / 2]; 
for (int i = 0; i < bytes.Length; i++) 
{ 
try 
{ 
// 每两个字符是一个 byte。 
bytes[i] = byte.Parse(hex.Substring(i * 2, 2), 
System.Globalization.NumberStyles.HexNumber); 
} 
catch 
{ 
// Rethrow an exception with custom message. 
throw new ArgumentException("hex is not a valid hex number!", "hex"); 
} 
} 
System.Text.Encoding chs = System.Text.Encoding.GetEncoding(charset); 
return chs.GetString(bytes); 
} 

详细出处参考：http://www.ogeek.net/article/18147.htm