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POWhat is the fastest way to iterate a dynamic object in C#?
 

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  1. POWhat is the fastest way to iterate a dynamic object in C#?
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    <h1>Background</h1> <p>I am working on an application that requires the consumption of JSON services on the <em>server</em>, and then repackaging of that JSON into a view model that can be referenced using Razor syntax in the view. Server-side manipulation of this code is a must for various reasons.</p> <p>We are using C#, .NET 4, MVC3, Razor, JsonFx.</p> <p>We currently have code that works just fine, but it is taking up to a minute to iterate 250 items in the received JSON object and this is unacceptable (not to mention baffling). I have already isolated the problem to the following loop; the JSON comes in lightening-fast so that is not the problem. Here is the <em>working but extremely slow</em> code:</p> <pre><code> var reader = new JsonReader(); var json = GetJson(SPListName); var admItems = new List&lt;IDictionary&lt;String, object&gt;&gt;(); dynamic _items = reader.Read(json); //This part is REALLY fast. No problem here. foreach (var itm in _items) { dynamic obj = new ExpandoObject(); foreach (dynamic admObj in itm)//Here begins the slow part. { var item = obj as IDictionary&lt;String, object&gt;; var encodedValue = ""; try { if(admObj.Key == "Title") { encodedValue = admObj.Value.ToString(); }else { encodedValue = admObj.Value[0].ToString(); } } catch (Exception) { encodedValue = admObj.Value.ToString(); } item[admObj.Key] = encodedValue.EncodeNonAscii().FixHtmlEntities(); } admItems.Add(obj); } return admItems; </code></pre> <p>You may also notice a few custom extension methods. Here they are (in case that matters):</p> <pre><code>public static string EncodeNonAscii(this Object str) { StringBuilder sb = new StringBuilder(); foreach (char c in str.ToString()) { if (c &gt; 127) { // This character is too big for ASCII string encodedValue = "\\u" + ((int) c).ToString("x4"); sb.Append(encodedValue); } else { sb.Append(c); } } return sb.ToString(); } public static string FixHtmlEntities(this Object str) { var fixedString = str.ToString().Replace("\\u00c2\\u00ae", "&amp;reg;"); return fixedString; } </code></pre> <h1>Question</h1> <p>What the heck am I doing wrong/how do I speed this up. My brain is hamburger right now so I hope someone points out a simple oversight.</p> <h1>Update/Resolution</h1> <p>Rophuine and Joshua Enfield both pointed to the root of the speed issue: the catching of exceptions was slowing everything down. </p> <p>Many folks suggested that I use Json.Net or something similar. While I appreciate that advice, it really wasn't at the root of my problem (even though it may have appeared that way); I have used Json.Net extensively in the past and came to prefer <a href="http://jsonfx.net/" rel="nofollow">JsonFx</a> over it a few months ago. In this particular case, I am more concerned with the <em>construction</em> of a view model object as I have already deserialized the JSON using JsonFx. Please let me know if you still think I am missing your point ;).</p> <p>The reason for my brain-dead try/catch scheme was that I needed to do different things with each property of the JSON string depending on it's type (string, string[], object[], etc). I forgot that System.Type can handle that for me. So here is the final code:</p> <pre><code>var reader = new JsonReader(); var json = GetJson(SPListName); var admItems = new List&lt;IDictionary&lt;String, object&gt;&gt;(); dynamic _items = reader.Read(json); foreach (var itm in _items) { dynamic obj = new ExpandoObject(); foreach (dynamic admObj in itm) { var item = obj as IDictionary&lt;String, object&gt;; var encodedValue = ""; Type typeName = admObj.Value.GetType(); switch (typeName.ToString()) { case("System.String[]"): encodedValue = admObj.Value[0].ToString(); break; default: encodedValue = admObj.Value.ToString(); break; } item[admObj.Key] = encodedValue.EncodeNonAscii().FixHtmlEntities(); } admItems.Add(obj); } return admItems; </code></pre> <p>Hope this helps someone!</p>
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    1. USMatt Cashatt
    1. USMatt Cashatt
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    1. COHow many exceptions are occuring? If it's border-line flow control exception handling may be slowing you down some, but a minute sounds awfully long for 250 items. Do you really need to use dynamic here?
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      1. USJoshua Enfield
    2. COAre there any reason you don't use json library such as JSON.NET or ServiceStack.NET? It's easier (and also fast) to parse json string.
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      1. USKhairuddin Ni'am
    3. COIn addition to @Ni'am, you can have a dictionary of objects with a single line of code `JsonConvert.DeserializeObject`. Examples: http://stackoverflow.com/questions/8662233/parsing-non-standard-json/8662323#8662323 http://stackoverflow.com/questions/8887029/parsing-json-file-c-sharp/8887177#8887177
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