public string UnicodeToString(string unicode)
{
    string result = "";
    //正则匹配
    Regex reg = new Regex(@"(?i)//u([0-9a-f]{4})");
    result = reg.Replace(unicode, delegate (Match m)
    {
        return ((char)Convert.ToInt32(m.Groups[1].Value, 16)).ToString();
    });
    return result;
}

public static string StringToUnicode(string value)
{
    byte[] bytes = Encoding.Unicode.GetBytes(value);
    StringBuilder str= new StringBuilder();
    for (int i = 0; i < bytes.Length; i += 2)
    {
        // 取两个字符，每个字符都是右对齐。
        str.AppendFormat("u{0}{1}", bytes[i + 1].ToString("x").PadLeft(2, '0'), bytes[i].ToString("x").PadLeft(2, '0'));
    }
    return str.ToString();
}