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254 lines
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<title>LINQ to JSON</title>
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<div id="control">
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<span class="productTitle">Json.NET - Quick Starts & API Documentation</span><br />
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<span class="topicTitle">LINQ to JSON</span></div>
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<div id="content">
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<span style="color: DarkGray"> </span>
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<p>LINQ to JSON is a programming API for working with JSON objects. The API has been designed with LINQ in mind to enable to quick querying and creation of JSON objects. LINQ to JSON sits under the <a href="./html/N_Newtonsoft_Json_Linq.htm">Newtonsoft.Json.Linq</a> namespace.</p>
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<h3>Creating JSON</h3>
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<p>There are a number of different options when it comes to creating JSON using LINQ to JSON. The first to create objects imperatively. You have total control but it is more verbose than other options.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: #2b91af;">JArray</span> array = <span style="color: blue;">new</span> <span style="color: #2b91af;">JArray</span>();</pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">JValue</span> text = <span style="color: blue;">new</span> <span style="color: #2b91af;">JValue</span>(<span style="color: #a31515;">"Manual text"</span>);</pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">JValue</span> date = <span style="color: blue;">new</span> <span style="color: #2b91af;">JValue</span>(<span style="color: blue;">new</span> <span style="color: #2b91af;">DateTime</span>(2000, 5, 23));</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;">array.Add(text);</pre>
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<pre style="margin: 0px;">array.Add(date);</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: blue;">string</span> json = array.ToString();</pre>
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<pre style="margin: 0px;"><span style="color: green;">// [</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "Manual text",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "\/Date(958996800000+1200)\/"</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// ]</span></pre>
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</div>
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</div></div>
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<p>Another option is to create JSON objects declaratively.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: #2b91af;">List</span><<span style="color: #2b91af;">Post</span>> posts = GetPosts();</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">JObject</span> rss =</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JObject</span>(</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"channel"</span>,</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JObject</span>(</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"title"</span>, <span style="color: #a31515;">"James Newton-King"</span>),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"link"</span>, <span style="color: #a31515;">"http://james.newtonking.com"</span>),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"description"</span>, <span style="color: #a31515;">"James Newton-King's blog."</span>),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"item"</span>,</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JArray</span>(</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">from</span> p <span style="color: blue;">in</span> posts</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">orderby</span> p.Title</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">select</span> <span style="color: blue;">new</span> <span style="color: #2b91af;">JObject</span>(</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"title"</span>, p.Title),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"description"</span>, p.Description),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"link"</span>, p.Link),</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JProperty</span>(<span style="color: #a31515;">"category"</span>,</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">new</span> <span style="color: #2b91af;">JArray</span>(</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">from</span> c <span style="color: blue;">in</span> p.Categories</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">select</span> <span style="color: blue;">new</span> <span style="color: #2b91af;">JValue</span>(c)))))))));</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">Console</span>.WriteLine(rss.ToString());</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: green;">//{</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "channel": {</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "title": "James Newton-King",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "link": "http://james.newtonking.com",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "description": "James Newton-King's blog.",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "item": [</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// {</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "title": "Json.NET 1.3 + New license + Now on CodePlex",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "description": "Annoucing the release of Json.NET 1.3, the MIT license and the source being available on CodePlex",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "link": "http://james.newtonking.com/projects/json-net.aspx",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "category": [</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "Json.NET",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "CodePlex"</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// ]</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// },</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// {</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "title": "LINQ to JSON beta",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "description": "Annoucing LINQ to JSON",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "link": "http://james.newtonking.com/projects/json-net.aspx",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "category": [</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "Json.NET",</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// "LINQ"</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// ]</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// }</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// ]</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">// }</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">//}</span></pre>
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</div>
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</div></div>
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<p>You can create a JSON object from a non-JSON type using the <a href="./html/M_Newtonsoft_Json_Linq_JObject_FromObject.htm">FromObject</a> method.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: #2b91af;">JObject</span> o = <span style="color: #2b91af;">JObject</span>.FromObject(<span style="color: blue;">new</span></pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> channel = <span style="color: blue;">new</span></pre>
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<pre style="margin: 0px;"> {</pre>
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<pre style="margin: 0px;"> title = <span style="color: #a31515;">"James Newton-King"</span>,</pre>
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<pre style="margin: 0px;"> link = <span style="color: #a31515;">"http://james.newtonking.com"</span>,</pre>
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<pre style="margin: 0px;"> description = <span style="color: #a31515;">"James Newton-King's blog."</span>,</pre>
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<pre style="margin: 0px;"> item =</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">from</span> p <span style="color: blue;">in</span> posts</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">orderby</span> p.Title</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">select</span> <span style="color: blue;">new</span></pre>
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<pre style="margin: 0px;"> {</pre>
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<pre style="margin: 0px;"> title = p.Title,</pre>
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<pre style="margin: 0px;"> description = p.Description,</pre>
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<pre style="margin: 0px;"> link = p.Link,</pre>
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<pre style="margin: 0px;"> category = p.Categories</pre>
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<pre style="margin: 0px;"> }</pre>
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<pre style="margin: 0px;"> }</pre>
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<pre style="margin: 0px;">});</pre>
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</div>
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</div></div>
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<p>Finally JSON objects can be created from a string use the <a href="./html/M_Newtonsoft_Json_Linq_JObject_Parse.htm">Parse</a> method.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: blue;">string</span> json = <span style="color: #a31515;">@"{</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> CPU: 'Intel',</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> Drives: [</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> 'DVD read/writer',</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""500 gigabyte hard drive""</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ]</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;">}"</span>;</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">JObject</span> o = <span style="color: #2b91af;">JObject</span>.Parse(json);</pre>
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</div>
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</div></div>
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<h3>Querying JSON</h3>
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<p>The properties methods that are the most useful when querying JSON objects are
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the <a href="./html/Overload_Newtonsoft_Json_Linq_JToken_Children.htm">Children</a>
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method and the <a href="./html/P_Newtonsoft_Json_Linq_JToken_Item.htm">property index</a>.</p>
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<p>Children returns all the children of that object. If it is a JObject it will
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return a collection of properties to work with and if it is a JArray you will
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get a collection of the array's values.</p>
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<p>The property index is used to get a specific child, either by index position for JSON arrays or property name for JSON objects.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: blue;">var</span> postTitles =</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">from</span> p <span style="color: blue;">in</span> rss[<span style="color: #a31515;">"channel"</span>][<span style="color: #a31515;">"item"</span>].Children()</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">select</span> (<span style="color: blue;">string</span>)p[<span style="color: #a31515;">"title"</span>];</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: blue;">foreach</span> (<span style="color: blue;">var</span> item <span style="color: blue;">in</span> postTitles)</pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: #2b91af;">Console</span>.WriteLine(item);</pre>
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<pre style="margin: 0px;">}</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: green;">//LINQ to JSON beta</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">//Json.NET 1.3 + New license + Now on CodePlex</span></pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: blue;">var</span> categories =</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">from</span> c <span style="color: blue;">in</span> rss[<span style="color: #a31515;">"channel"</span>][<span style="color: #a31515;">"item"</span>].Children()[<span style="color: #a31515;">"category"</span>].Values<<span style="color: blue;">string</span>>()</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">group</span> c <span style="color: blue;">by</span> c <span style="color: blue;">into</span> g</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">orderby</span> g.Count() <span style="color: blue;">descending</span></pre>
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<pre style="margin: 0px;"> <span style="color: blue;">select</span> <span style="color: blue;">new</span> { Category = g.Key, Count = g.Count() };</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: blue;">foreach</span> (<span style="color: blue;">var</span> c <span style="color: blue;">in</span> categories)</pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: #2b91af;">Console</span>.WriteLine(c.Category + <span style="color: #a31515;">" - Count: "</span> + c.Count);</pre>
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<pre style="margin: 0px;">}</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: green;">//Json.NET - Count: 2</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">//LINQ - Count: 1</span></pre>
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<pre style="margin: 0px;"><span style="color: green;">//CodePlex - Count: 1</span></pre>
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</div>
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</div></div>
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<p>LINQ to JSON can also be used to manually convert from JSON to a .NET object.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: blue;">public</span> <span style="color: blue;">class</span> <span style="color: #2b91af;">Shortie</span></pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">string</span> Original { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">string</span> Shortened { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">string</span> Short { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: #2b91af;">ShortieException</span> Error { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;">}</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: blue;">public</span> <span style="color: blue;">class</span> <span style="color: #2b91af;">ShortieException</span></pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">int</span> Code { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">string</span> ErrorMessage { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;">}</pre>
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</div>
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</div></div>
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<p>Manually serializing and deserializing between .NET objects is most useful when working with JSON that doesn't closely match your .NET objects.</p>
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<div class="overflowpanel"> <div class="code">
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<div style="font-family: Courier New; font-size: 10pt; color: black;">
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<pre style="margin: 0px;"><span style="color: blue;">string</span> jsonText = <span style="color: #a31515;">@"{</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""short"":{</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""original"":""http://www.foo.com/"",</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""short"":""krehqk"",</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""error"":{</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""code"":0,</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;"> ""msg"":""No action taken""}</span></pre>
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<pre style="margin: 0px;"><span style="color: #a31515;">}"</span>;</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">JObject</span> json = <span style="color: #2b91af;">JObject</span>.Parse(jsonText);</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">Shortie</span> shortie = <span style="color: blue;">new</span> <span style="color: #2b91af;">Shortie</span></pre>
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<pre style="margin: 0px;"> {</pre>
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<pre style="margin: 0px;"> Original = (<span style="color: blue;">string</span>)json[<span style="color: #a31515;">"short"</span>][<span style="color: #a31515;">"original"</span>],</pre>
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<pre style="margin: 0px;"> Short = (<span style="color: blue;">string</span>)json[<span style="color: #a31515;">"short"</span>][<span style="color: #a31515;">"short"</span>],</pre>
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<pre style="margin: 0px;"> Error = <span style="color: blue;">new</span> <span style="color: #2b91af;">ShortieException</span></pre>
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<pre style="margin: 0px;"> {</pre>
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<pre style="margin: 0px;"> Code = (<span style="color: blue;">int</span>)json[<span style="color: #a31515;">"short"</span>][<span style="color: #a31515;">"error"</span>][<span style="color: #a31515;">"code"</span>],</pre>
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<pre style="margin: 0px;"> ErrorMessage = (<span style="color: blue;">string</span>)json[<span style="color: #a31515;">"short"</span>][<span style="color: #a31515;">"error"</span>][<span style="color: #a31515;">"msg"</span>]</pre>
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<pre style="margin: 0px;"> }</pre>
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<pre style="margin: 0px;"> };</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">Console</span>.WriteLine(shortie.Original);</pre>
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<pre style="margin: 0px;"><span style="color: green;">// http://www.foo.com/</span></pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"><span style="color: #2b91af;">Console</span>.WriteLine(shortie.Error.ErrorMessage);</pre>
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<pre style="margin: 0px;"><span style="color: green;">// No action taken</span></pre>
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</div>
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</div></div>
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<div id="footer"></div>
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</html> |