/// <summary>
/// GB2312转换成UTF8
/// </summary>
/// <param name="text"></param>
/// <returns></returns>
public static string gb2312_utf8(string text)
{
    //声明字符集   
    System.Text.Encoding utf8, gb2312;
    //gb2312   
    gb2312 = System.Text.Encoding.GetEncoding("gb2312");
    //utf8   
    utf8 = System.Text.Encoding.GetEncoding("utf-8");
    byte[] gb;
    gb = gb2312.GetBytes(text);
    gb = System.Text.Encoding.Convert(gb2312, utf8, gb);
    //返回转换后的字符   
    return utf8.GetString(gb);
}

/// <summary>
/// UTF8转换成GB2312
/// </summary>
/// <param name="text"></param>
/// <returns></returns>
public static string utf8_gb2312(string text)
{
   //声明字符集   
   System.Text.Encoding utf8, gb2312;
   //utf8   
   utf8 = System.Text.Encoding.GetEncoding("utf-8");
   //gb2312   
   gb2312 = System.Text.Encoding.GetEncoding("gb2312");
   byte[] utf;
   utf = utf8.GetBytes(text);
   utf = System.Text.Encoding.Convert(utf8, gb2312, utf);
   //返回转换后的字符   
   return gb2312.GetString(utf);
}