Qr's blog--How to convert XML to JSON in ASP.NET C#

How to convert XML to JSON in ASP.NET C#

2010/7/16 0:06:30

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. Code to convert XML to JSON in ASP.NET C# Example of how to insert JSON code into a page when the page is generated Please acknowledge PHD Computer Consultants Ltd (PHDCC) if you use this code 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 DescriptionThe code provides a method private 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. ExampleThe 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# codeYou 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> 原文出自：http://www.phdcc.com/xml2json.htm

Posted by Qr on 2010/7/16 0:06:30