我们一般在用JSON或者XML作为数据交换的时候，可能定义一个没有真正意义方法的类，其实就是一个关于属性的数据结构，如果对于这种情况，可以将这个类对象作为中介，然后利用C#提供的序列化和反序列化的方法。今天看到一个别人封装好的感觉不错，就转载：
private static string XmlToJSON(XmlDocument xmlDoc)
{
    StringBuilder sbJSON = new StringBuilder();
    sbJSON.Append("{ ");
    XmlToJSONnode(sbJSON, xmlDoc.DocumentElement, true);
    sbJSON.Append("}");
    return sbJSON.ToString();
}

//  XmlToJSONnode:  Output an XmlElement, possibly as part of a higher array
private static void XmlToJSONnode(StringBuilder sbJSON, XmlElement node, bool showNodeName)
{
    if (showNodeName)
        sbJSON.Append("\"" + SafeJSON(node.Name) + "\": ");
    sbJSON.Append("{");
    // Build a sorted list of key-value pairs
    //  where   key is case-sensitive nodeName
    //          value is an ArrayList of string or XmlElement
    //  so that we know whether the nodeName is an array or not.
    SortedList childNodeNames = new SortedList();

    //  Add in all node attributes
    if( node.Attributes!=null)
        foreach (XmlAttribute attr in node.Attributes)
            StoreChildNode(childNodeNames,attr.Name,attr.InnerText);

    //  Add in all nodes
    foreach (XmlNode cnode in node.ChildNodes)
    {
        if (cnode is XmlText)
            StoreChildNode(childNodeNames, "value", cnode.InnerText);
        else if (cnode is XmlElement)
            StoreChildNode(childNodeNames, cnode.Name, cnode);
    }

    // Now output all stored info
    foreach (string childname in childNodeNames.Keys)
    {
        ArrayList alChild = (ArrayList)childNodeNames[childname];
        if (alChild.Count == 1)
            OutputNode(childname, alChild[0], sbJSON, true);
        else
        {
            sbJSON.Append(" \"" + SafeJSON(childname) + "\": [ ");
            foreach (object Child in alChild)
                OutputNode(childname, Child, sbJSON, false);
            sbJSON.Remove(sbJSON.Length - 2, 2);
            sbJSON.Append(" ], ");
        }
    }
    sbJSON.Remove(sbJSON.Length - 2, 2);
    sbJSON.Append(" }");
}

//  StoreChildNode: Store data associated with each nodeName
//                  so that we know whether the nodeName is an array or not.
private static void StoreChildNode(SortedList childNodeNames, string nodeName, object nodeValue)
{
    // Pre-process contraction of XmlElement-s
    if (nodeValue is XmlElement)
    {
        // Convert  <aa></aa> into "aa":null
        //          <aa>xx</aa> into "aa":"xx"
        XmlNode cnode = (XmlNode)nodeValue;
        if( cnode.Attributes.Count == 0)
        {
            XmlNodeList children = cnode.ChildNodes;
            if( children.Count==0)
                nodeValue = null;
            else if (children.Count == 1 && (children[0] is XmlText))
                nodeValue = ((XmlText)(children[0])).InnerText;
        }
    }
    // Add nodeValue to ArrayList associated with each nodeName
    // If nodeName doesn't exist then add it
    object oValuesAL = childNodeNames[nodeName];
    ArrayList ValuesAL;
    if (oValuesAL == null)
    {
        ValuesAL = new ArrayList();
        childNodeNames[nodeName] = ValuesAL;
    }
    else
        ValuesAL = (ArrayList)oValuesAL;
    ValuesAL.Add(nodeValue);
}

private static void OutputNode(string childname, object alChild, StringBuilder sbJSON, bool showNodeName)
{
    if (alChild == null)
    {
        if (showNodeName)
            sbJSON.Append("\"" + SafeJSON(childname) + "\": ");
        sbJSON.Append("null");
    }
    else if (alChild is string)
    {
        if (showNodeName)
            sbJSON.Append("\"" + SafeJSON(childname) + "\": ");
        string sChild = (string)alChild;
        sChild = sChild.Trim();
        sbJSON.Append("\"" + SafeJSON(sChild) + "\"");
    }
    else
        XmlToJSONnode(sbJSON, (XmlElement)alChild, showNodeName);
    sbJSON.Append(", ");
}

// Make a string safe for JSON
private static string SafeJSON(string sIn)
{
    StringBuilder sbOut = new StringBuilder(sIn.Length);
    foreach (char ch in sIn)
    {
        if (Char.IsControl(ch) || ch == '\'')
        {
            int ich = (int)ch;
            sbOut.Append(@"\u" + ich.ToString("x4"));
            continue;
        }
        else if (ch == '\"' || ch == '\\' || ch == '/')
        {
            sbOut.Append('\\');
        }
        sbOut.Append(ch);
    }
    return sbOut.ToString();
}

/// <summary>
        /// json字符串转换为Xml对象
        /// </summary>
        /// <param name="sJson"></param>
        /// <returns></returns>
        public static XmlDocument Json2Xml(string sJson)
        {
            //XmlDictionaryReader reader = JsonReaderWriterFactory.CreateJsonReader(Encoding.UTF8.GetBytes(sJson), XmlDictionaryReaderQuotas.Max);
            //XmlDocument doc = new XmlDocument();
            //doc.Load(reader);

            JavaScriptSerializer oSerializer = new JavaScriptSerializer();
            Dictionary<string, object> Dic = (Dictionary<string, object>)oSerializer.DeserializeObject(sJson);
            XmlDocument doc = new XmlDocument();
            XmlDeclaration xmlDec;
            xmlDec = doc.CreateXmlDeclaration("1.0", "gb2312", "yes");
            doc.InsertBefore(xmlDec, doc.DocumentElement);
            XmlElement nRoot = doc.CreateElement("root");
            doc.AppendChild(nRoot);
            foreach (KeyValuePair<string, object> item in Dic)
            {
                XmlElement element = doc.CreateElement(item.Key);
                KeyValue2Xml(element, item);
                nRoot.AppendChild(element);
            }
            return doc;
        }

        private static void KeyValue2Xml(XmlElement node, KeyValuePair<string, object> Source)
        {
            object kValue = Source.Value;
            if (kValue.GetType() == typeof(Dictionary<string, object>))
            {
                foreach (KeyValuePair<string, object> item in kValue as Dictionary<string, object>)
                {
                    XmlElement element = node.OwnerDocument.CreateElement(item.Key);
                    KeyValue2Xml(element, item);
                    node.AppendChild(element);
                }
            }
            else if (kValue.GetType() == typeof(object[]))
            {
                object[] o = kValue as object[];
                for (int i = 0; i < o.Length; i++)
                {
                    XmlElement xitem = node.OwnerDocument.CreateElement("Item");
                    KeyValuePair<string, object> item = new KeyValuePair<string, object>("Item", o[i]);
                    KeyValue2Xml(xitem, item);
                    node.AppendChild(xitem);
                }
                   
            }
            else
            {
                XmlText text = node.OwnerDocument.CreateTextNode(kValue.ToString());
                node.AppendChild(text);
            }
        }