Json.NET: convert JSON string to XML or XML to JSON string

Thanks for David Brown's answer. In my case of JSON.Net 3.5, the convert methods are under the JsonConvert static class:

XmlNote myXmlNode = JsonConvert.DeserializeXmlNode(myJsonString);
// or .DeserilizeXmlNode(myJsonString, "root"); // if myJsonString does not have a root
string jsonString = JsonConvert.SerializeXmlNode(myXmlNode);

Yes, you can do it (I do) but Be aware of some paradoxes when converting, and handle appropriately. Keep in mind I am using the default settings with Newtonsoft json library and MS XML library, so your mileage may vary:

XML->JSON

1. All data becomes string data (for example you will always get "false" not false or "0" not 0) Obviously javascript treats these differently in certain cases.
2. Children elements can become sub object OR sub array depending if there is only one or more than one child element. You would consume these two differently in javascript. The same valid XML can produce actually different JSON structures this way. You can add the attribute json:Array='true' to your element to workaround this in some cases.
3. Your XML must be fairly well-formed, I have noticed it doesnt need to perfectly conform to W3C standard, but 1. you must have a root element and 2. you cannot start element names with numbers are two of the enforced XML standards I have found when using Newtonsoft and MS libraries.
4. Blank elements do not convert to JSON. They are ignored. A blank element does not become "element":null

JSON->XML

1. You need a top level object that will convert to a root XML element or the parser will fail.
2. Your object names cannot start with a number, as they cannot be converted to elements (XML is techically even more strict than this, but I can 'get away' with breaking all? the other element naming rules.

Please feel free to mention any other issues you have noticed, I have developed my own custom routines for preparing and cleaning the strings as I convert back and forth. Your situation may or may not call for prep/cleanup.

Here is a blog that tells about conversion of XML to JSON and JSON to XML: http://sandeep-aparajit.blogspot.com/2010/01/json-to-xml-and-xml-to-json-converter.html

Try this function. I just wrote it and haven't had much of a chance to test it, but my preliminary tests are promising.

public static XmlDocument JsonToXml(string json)
    {
        XmlNode newNode = null;
        XmlNode appendToNode = null;
        XmlDocument returnXmlDoc = new XmlDocument();
        returnXmlDoc.LoadXml("<Document />");
        XmlNode rootNode = returnXmlDoc.SelectSingleNode("Document");
        appendToNode = rootNode;

        string[] arrElementData;
        string[] arrElements = json.Split('\r');
        foreach (string element in arrElements)
        {
            string processElement = element.Replace("\r", "").Replace("\n", "").Replace("\t", "").Trim();
            if ((processElement.IndexOf("}") > -1 || processElement.IndexOf("]") > -1) &&
                appendToNode != rootNode)
            {
                appendToNode = appendToNode.ParentNode;
            }
            else if (processElement.IndexOf("[") > -1)
            {
                processElement = processElement.Replace(":", "").Replace("[", "").Replace("\"", "").Trim();
                newNode = returnXmlDoc.CreateElement(processElement);
                appendToNode.AppendChild(newNode);
                appendToNode = newNode;
            }
            else if (processElement.IndexOf("{") > -1 && processElement.IndexOf(":") > -1)
            {
                processElement = processElement.Replace(":", "").Replace("{", "").Replace("\"", "").Trim();
                newNode = returnXmlDoc.CreateElement(processElement);
                appendToNode.AppendChild(newNode);
                appendToNode = newNode;
            }
            else
            {
                if (processElement.IndexOf(":") > -1)
                {
                    arrElementData = processElement.Replace(": \"", ":").Replace("\",", "").Replace("\"", "").Split(':');
                    newNode = returnXmlDoc.CreateElement(arrElementData[0]);
                    for (int i = 1; i < arrElementData.Length; i++)
                    { newNode.InnerText += arrElementData[i]; }
                    appendToNode.AppendChild(newNode);
                }
            }
        }

        return returnXmlDoc;
    }

I searched for a long time to find alternative code to the accepted solution in the hopes of not using an external assembly / project. I came up with the following thanks to the source code of the DynamicJson project:

public XmlDocument JsonToXML(string json)
    {
        XmlDocument doc = new XmlDocument();

        using (var reader = JsonReaderWriterFactory.CreateJsonReader(Encoding.UTF8.GetBytes(json), XmlDictionaryReaderQuotas.Max))
        {
            XElement xml = XElement.Load(reader);
            doc.LoadXml(xml.ToString());
        }

        return doc;
    }

Note: I wanted an XmlDocument rather than an XElement for xPath purposes. Also, this code obviously only goes from json to Xml, there are various ways to do the opposite.

mmhhh... I found some problems in this code, if for example the document didn't have any line feed, the code could not work (I have to convert a "only one line json document"). Also, it was changing a lot of my data (I have : and " in the data values). But it was a very good start for me to implement the procedure. I publish it, just:

1. It is written in vb.net, not c# sorry

2. It is not optimized, it is written in a "safe" and "debug-friendly" way

   Private Function JsonToXml(ByVal json As String) As XmlDocument
   Dim newNode As XmlNode = Nothing
   Dim appendToNode As XmlNode = Nothing
   Dim returnXmlDoc As XmlDocument = New XmlDocument
   returnXmlDoc.LoadXml("<Document />")
   Dim rootNode As XmlNode = returnXmlDoc.SelectSingleNode("Document")
   appendToNode = rootNode
   
   json = json.Replace(",", "," & vbLf)
   json = json.Replace("{", "{" & vbLf)
   json = json.Replace("}", vbLf & "}" & vbLf)
   json = json.Replace("[", "[" & vbLf)
   json = json.Replace("]", vbLf & "]" & vbLf)
   
   Dim arrElementData() As String
   Dim arrElements() As String = json.Split(vbLf)
   For Each element As String In arrElements
       Dim processElement As String = element.Replace(vbLf, "").Replace(vbCr, "").Replace(vbTab, "").Trim()
       If processElement.Trim <> "" Then
           If (processElement.IndexOf("}") > -1 Or processElement.IndexOf("]") > -1) And Not (appendToNode Is rootNode) Then
               appendToNode = appendToNode.ParentNode
           ElseIf (processElement.IndexOf("[") > -1) Then
               processElement = processElement.Replace(":", "").Replace("[", "").Replace("""", "").Trim()
               If processElement.Trim = "" Then
                   processElement = "Square"
               End If
               newNode = returnXmlDoc.CreateElement(processElement)
               appendToNode.AppendChild(newNode)
               appendToNode = newNode
           ElseIf (processElement.IndexOf("{") > -1) Then
               processElement = processElement.Replace(":", "").Replace("{", "").Replace("""", "").Trim()
               If processElement.Trim = "" Then
                   processElement = "Element"
               End If
               newNode = returnXmlDoc.CreateElement(processElement)
               appendToNode.AppendChild(newNode)
               appendToNode = newNode
           Else
               Dim FoundAt As Integer = processElement.IndexOf(":")
               If (FoundAt > -1) Then
                   Dim NodeName As String = processElement.Substring(0, FoundAt - 1).Replace("""", "")
                   Dim NodeValue As String = processElement.Substring(FoundAt + 1, processElement.Length - FoundAt - 1).Trim
                   If NodeValue.StartsWith("""") Then
                       NodeValue = NodeValue.Substring(1, NodeValue.Length - 1).Trim
                   End If
                   If NodeValue.EndsWith(",") Then
                       NodeValue = NodeValue.Substring(0, NodeValue.Length - 1).Trim
                   End If
                   If NodeValue.EndsWith("""") Then
                       NodeValue = NodeValue.Substring(0, NodeValue.Length - 1).Trim
                   End If
                   newNode = returnXmlDoc.CreateElement(NodeName)
                   newNode.InnerText = NodeValue
                   appendToNode.AppendChild(newNode)
               End If
           End If
       End If
   Next
   Return returnXmlDoc
    End Function
   

Ciao, Michele