留爪参考

using System.Xml; //
using System.Text; //
using System.Runtime.Serialization.Json; //JsonReaderWriterFactory
//以下method引用以上using

    /// <summary>
    /// Json字符串转xml字符串(utf-8)
    /// </summary>
    /// <param name="json">json字符串</param>
    /// <returns>xml字符串</returns>
    public string JsonToXml(string json)
    {
        string xml = string.Empty;
        XmlDocument xmlDoc = new XmlDocument();
        try
        {
            XmlDictionaryReader xmlReader = JsonReaderWriterFactory.CreateJsonReader(Encoding.UTF8.GetBytes(json), XmlDictionaryReaderQuotas.Max);
            xmlDoc.Load(xmlReader);
            //json转xml

            XmlDeclaration xmlDec = xmlDoc.CreateXmlDeclaration("1.0", "utf-8", "yes");
            //创建xml声明
            xmlDoc.InsertBefore(xmlDec, xmlDoc.DocumentElement); //插入xml声明
            //xmlDoc.AppendChild(xmlDec);
            //添加xml声明
        }
        catch (Exception ex)
        {          
            //
        }
        return xmlDoc.OuterXml; //xml转string
    }