C#字符集编码的使用及说明

public static int GetGBKValue(string key)
 {
            byte[] gbk = Encoding.GetEncoding("GBK").GetBytes(key);
            //或者byte[] gbk = Encoding.UTF8.GetBytes(key);
            
            string code = "";
            foreach (byte b in gbk)
            {
                code += string.Format("{0:X2}", b);
            }
            int gbkValue = int.Parse(code, NumberStyles.HexNumber);
            return gbkValue;
 }

using System.Text;
...
public static string UTF8ToGBK(string text)
        {
            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            try
            {
                Encoding utf8 = Encoding.UTF8;
                Encoding gbk = Encoding.GetEncoding("gbk");//Encoding.Default ,936
                byte[] temp = utf8.GetBytes(text);
                byte[] temp1 = Encoding.Convert(utf8, gbk, temp);
                string result = gbk.GetString(temp1);
                return result;
            }
            catch
            {
                return null;
            }
        }
        
public static string GBKToUTF8(string str)
        {
            Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
            Encoding utf8;
            Encoding gbk;
            utf8 = Encoding.GetEncoding("utf-8");
            gbk = Encoding.GetEncoding("gbk");
            byte[] gb = gbk.GetBytes(str);
            gb = Encoding.Convert(gbk, utf8, gb);
            return utf8.GetString(gb);
        }