How to convert XML to JSON in ASP.NET C#
Last modified: 18 July 2006. Any comments or suggestions - please fill in form below. Chris Cant.
No download provided - cut and paste to try out. The following code is provided as-is without any warranty of any kind.
Introduction
JSON is a lightweight data-interchange format. It is particularly useful because it can be 'decoded' easily by web page JavaScript into object form.
AJAX-based web pages use XmlHttpRequest to receive data from a server in response to a user action. While the returned data is normally in XML format, it can also be returned in JSON string format and processed more easily in JavaScript.
Many applications may store information in XML format. However they may want to send data to a client using JSON. To achieve this, they must convert their XML data into JSON format. The ASP.NET C# code below does this job.
Code Description
The code provides a methodprivate static string XmlToJSON(XmlDocument xmlDoc) that converts an XmlDocument into a JSON string. The code iterates through each XML element, its attributes and children, creating the corresponding JSON objects.
- The code never generates number or boolean values.
- The XML documentElement is always reported as member:object even if it could be shortened by the following rules.
- Element attributes are converted into member "attr_name":"attr_value".
XML JSON <xx yy='nn'></xx> { "xx": {"yy":"nn"} } <xx yy=''></xx> { "xx": {"yy":""} } - Element children with no attributes, children or text are converted into member "child_name":null
XML JSON <xx/> { "xx":null } - Element children with no attributes or children but contain text are converted into "child_name":"child_text"
XML JSON <xx>yyy</xx> { "xx":"yyy" } - Other element attributes and children are converted into "child_name":object or an array "child_name":[elements] as appropriate, with element text converted into a member with name "value"
XML JSON <xx yy='nn'><mm>zzz</mm></xx> { "xx": {"yy":"nn", "mm":"zzz"} } <xx yy='nn'><mm>zzz</mm><mm>aaa</mm></xx> { "xx": {"yy":"nn", "mm": [ "zzz", "aaa" ] } } <xx><mm>zzz</mm>some text</xx> { "xx": {"mm":"zzz", "value":"some text"} } <xx value='yyy'>some text<mm>zzz</mm>more text</xx> { "xx": {"mm":"zzz", "value": [ "yyy", "some text", "more text" ] } } - Characters are made safe for conversion into JSON. Note that this does not protect your JavaScript from attack if any of the source XML comes from an unsafe source, eg user input.
XML JSON <aa>/z'z"z\yyy<aa>< {"aa": "\/z\u0027z\"z\\yyy" }
In some special circumstances, such as in the example below, you may need to escape the backslash characters again, eg:
string JSON = XmlToJSON(doc);
JSON = JSON.Replace(@"\", @"\\"); Note that there may be security implications for web pages using unchecked XML contents.
Example
The examples on this page come from my Space Browse site.XML Input:
<space name="Cake Collage"> <frame> <photo img="cakecollage1.jpg" /> <text string="Browse my cake space" /> <rule type="F" img="cakecollage9.jpg" x="150" y="0" w="300" h="250" /> <rule type="F" img="cakecollage2.jpg" x="0" y="0" w="150" h="220" /> </frame> <frame> <photo img="cakecollage2.jpg" /> <rule type="B" img="cakecollage1.jpg" /> <rule type="L" img="cakecollage3.jpg" /> </frame> </space>
JSON Output (re-formatted):
{ "space":
{ "name": "Cake Collage",
"frame": [ {"photo": { "img": "cakecollage1.jpg" },
"rule": [ { "type": "F",
"img": "cakecollage9.jpg",
"x": "150",
"y": "0",
"w": "300",
"h": "250"
},
{ "type": "F",
"img": "cakecollage2.jpg",
"x": "0",
"y": "0",
"w": "150",
"h": "220"
}
],
"text": { "string": "Browse my cake space" }
},
{"photo": { "img": "cakecollage2.jpg" },
"rule": [ { "type": "B", "img": "cakecollage1.jpg" },
{ "type": "L", "img": "cakecollage3.jpg" }
]
}
]
}
}
Once the JSON has been converted into a JavaScript object, eg called space_DOM, the following objects are available:
- space_DOM.space.name
- space_DOM.space.frame.length
- space_DOM.space.frame[0].text.string
- space_DOM.space.frame[0].rule[0].type
Your JavaScript code should be flexible to cope with members not existing, members existing as a single value, or members existing as an array. I find it useful to have a JavaScript function ObjectToArray which converts all these cases into an Array of length 0, 1 or greater.
function ObjectToArray( obj)
{
if( !obj) return new Array();
if( !obj.length) return new Array(obj);
return obj;
}
space_DOM.space.frame = ObjectToArray(space_DOM.space.frame);
XmlToJSON C# code
You may wish to use some of the updates suggsted in the comments below.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();
}
Using XmlToJSON
The following code shows how to use XmlToJSON() when an ASP.NET 2 page loads. It then uses the ASP.NET2 ClientScriptManager to insert code containing the JSON string into the web page. See the following section for an example of JavaScript space_processJSON().
protected void Page_Load(object sender, EventArgs e)
{
XmlDocument doc = new XmlDocument();
try
{
string path = Server.MapPath(".");
doc.Load(path+"whatever.xml");
}
catch (Exception ex)
{
lblError.Text = ex.ToString();
return;
}
// Convert XML to a JSON string
string JSON = XmlToJSON(doc);
// Replace \ with \\ because string is being decoded twice
JSON = JSON.Replace(@"\", @"\\");
// Insert code to process JSON at end of page
ClientScriptManager cs = Page.ClientScript;
cs.RegisterStartupScript(GetType(), "SpaceJSON", "space_processJSON('" + JSON + "');", true);
}
Client-side code
<script src="space/json.js" type="text/javascript"></script>
<script type="text/javascript">
function space_processJSON( JSON)
{
space_DOM = JSON.parseJSON();
if( !space_DOM)
{
alert("JSON decode error");
return;
}
space_DOM.space.frame = ObjectToArray(space_DOM.space.frame);
space_frameCount = space_DOM.space.frame.length;
.. or whatever
}
</script>
Comments:
- Michael, Mon, 19 Jun 2006 16:46:05 (GMT)
- See this implementation: http://groups.google.de/group/ajaxpro/browse_thread/thread/219f830011e5ca6f/9e72c85fcf802a84#9e72c85fcf802a84
- Damon Carr, Thu, 07 Sep 2006 12:24:31 (GMT)
- Excellent work.
- Alex Egg, Sun, 31 Dec 2006 06:31:43 (GMT)
- Question: Why is XmlToJSON private? Wouldn't it be more appropriate for this method to be declared as public? Also, I think you should change the XmlDocument parameter of XmlToJSON to an XmlNode, it would be much more versatile.
Also, I have discovered you code does not produce correct JSON when the xml contains cdata blocks - Eric Walker, Mon, 8 Oct 2007 08:01:45 -0700
- I found that an empty xml node was not being decoded properly (an extra } was being added). So for example <foo /> would be translated as {"foo" : }}
By tracking whether or not a child was added, I was able to work arround this issue:// XmlToJSONnode: Output an XmlElement, possibly as part of a higher array public static void XmlToJSONnode(StringBuilder sbJSON, XmlElement node, bool showNodeName) { bool childAdded = false; 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) { childAdded = true; 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) { childAdded = true; 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); if (childAdded) { sbJSON.Append(" }"); } else { sbJSON.Append(" null"); } }I hope this is helpful. - Leon, Mon, 22 Oct 2007 09:20:55 -0700
- Another way to do it (DataContractJsonSerializer):
http://blogs.msdn.com/kaevans/archive/2007/09/04/use-linq-and-net-3-5-to-convert-rss-to-json.aspx - Mark Brito, Tue, 19 Feb 2008 21:16:32 GMT
- In spirit of helping .. I found a bug where there is only one element in the xml, it would make it a single element instead of an array.. simply change the following line of code..
if (alChild.Count == 1)
toif (alChild.Count == 1 && (alChild[0] is string))
Below is the entire function.public static void XmlToJSONnode(StringBuilder sbJSON, XmlElement node, bool showNodeName) { bool childAdded = false; 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) { childAdded = true; 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) { childAdded = true; ArrayList alChild = (ArrayList)childNodeNames[childname]; bool bFlag = false; foreach (object oChild in alChild) bFlag = true; if (alChild.Count == 1 && (alChild[0] is string)) 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); if (childAdded) { sbJSON.Append(" }"); } else { sbJSON.Append(" null"); } } - Milind Amin, Fri, 25 Jul 2008 06:52:56 GMT
- Thanks. Very Good Article.
- Paul Chu, Thu, 16 Oct 2008 01:52:44 GMT
- Thank you and all the other contributors for this excellent article.
Does the last post contain all the suggested enhancements ?
Answer: I haven't tested the suggestions but they look good! - Chris, Thu, 13 Nov 2008 04:47:25 GMT
- I could see where this would come in handy. Hats off to you for that. Overall, I would prefer to build JSON from real objects which gives me the ability to serialize to XML, JSON, or whatever.
- noone, Mon, 06 Apr 2009 12:55:55 GMT
- Use the .NET 3.5 JavaScript Serializer: System.Web.Script.Serialization.JavaScriptSerializer
- Michele Costabile, Wed, 20 May 2009 13:33:31 GMT
- I had a problem with an extra brace at the end of the file. I solved it checking that I really had to remove two characters from the end of the string buffer in XmlToJSONnode. The following is my version of the function. Maybe further inspection of the code would be in order for finding a more elegant solution, but this is what I managed to do in a short time.
// 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 bool hasAddedChild = false; foreach (string childname in childNodeNames.Keys) { ArrayList alChild = (ArrayList)childNodeNames[childname]; if (alChild.Count == 1 && (alChild[0] is string)) { hasAddedChild = true; OutputNode(childname, alChild[0], sbJSON, true); } else { sbJSON.Append(" \"" + SafeJSON(childname) + "\": [ "); foreach (object Child in alChild) { hasAddedChild = true; OutputNode(childname, Child, sbJSON, false); } if (hasAddedChild) sbJSON.Remove(sbJSON.Length - 2, 2); sbJSON.Append(" ], "); } } if (hasAddedChild) sbJSON.Remove(sbJSON.Length - 2, 2); sbJSON.Append(" }"); } - Overide, Thu, 09 Jul 2009 11:09:49 GMT
- ObjectToArray(obj): function is incorrect if obj is String. Maybe better:
function ObjectToArray( obj) { if (!obj) return new Array(); if (!(obj instanceof Array)) return new Array(obj); return obj; } - Override, Fri, 10 Jul 2009 08:39:11 GMT
- and also it conflicts with JQuery. Line:
v = f(v);- not enough memory - lucky, Fri, 21 Aug 2009 01:29:39 GMT
- Thank
- Karl, Thu, 15 Oct 2009 23:46:49 GMT
- I added a check for numeric values, to optionally display the quotes.
In OutputNode() change the one line with the quotes to:
Double temp; if (Double.TryParse(sChild, out temp)) sbJSON.Append(SafeJSON(sChild)); else sbJSON.Append("\"" + SafeJSON(sChild) + "\"");
출처 : http://www.phdcc.com/xml2json.htm
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