把汉字字符转换成UTF-8的代码的方法

public string Conv(string inputString, string encodeName)
{
 if (inputString == null)
 {
  return null;
 }
 string tempValue=null;
 byte[] buf = new byte[inputString.Length];
 System.Text.Encoding.GetEncoding(encodeName).GetBytes(inputString, 0, inputString.Length, buf, 0);
 tempValue = System.Text.Encoding.Default.GetString(buf);
 return tempValue;
}