Parsing Twitter JSON data in C#

The Twitter API lets you return search results in either Atom or JSON. Atom is nice, because you can just throw it into an XMLDocument object and use XPath queries to get the results you’d like. But its obvious that the Tweets have been rather forcefully dumped into the various Atom fields and the JSON implementation is cleaner. But how do you parse that JSON in .Net?

There are loads of JSON serializers available for .Net, but very few parsers. It took me a while to find this one. It does the job well, but the JsonDecode() function has a rather unfriendly output which according to the comments can be:

/// An ArrayList, a Hashtable, a double, a string, null, true, or false

So which is it? Well the return type for a Twitter search query is a Hashtable:

HashTable jsonHash = (Hashtable)Procurios.Public.JSON.JsonDecode(jsonCode);

This contains a number of elements, including the search results themselves, which are in an element called [results]. The [results] element is actually an ArrayList:

ArrayList jsonResults = (ArrayList)jsonHash["results"];
foreach (object objResult in jsonResults) {

… and each ArrayList item is another Hashtable containing the details of each search result:

Hashtable jsonResult = (Hashtable)objResult;
System.Diagnostics.Debug.WriteLine("User ID: " + jsonResult["from_user_id"].ToString());
System.Diagnostics.Debug.WriteLine("Tweet text: " + jsonResult["text"].ToString());
System.Diagnostics.Debug.WriteLine("Tweet date: " + jsonResult["created_at"].ToString());
System.Diagnostics.Debug.WriteLine("User name: " + jsonResult["from_user"].ToString());
System.Diagnostics.Debug.WriteLine("Language: " + jsonResult["iso_language_code"].ToString())

The full code would be:

HashTable jsonHash = (Hashtable)Procurios.Public.JSON.JsonDecode(jsonCode);
ArrayList jsonResults = (ArrayList)jsonHash["results"];

foreach (object objResult in jsonResults)
{

	Hashtable jsonResult = (Hashtable)objResult;
	System.Diagnostics.Debug.WriteLine("User ID: "
				+ jsonResult["from_user_id"].ToString());
	System.Diagnostics.Debug.WriteLine("Tweet text: "
				+ jsonResult["text"].ToString());
	System.Diagnostics.Debug.WriteLine("Tweet date: "
				+ jsonResult["created_at"].ToString());
	System.Diagnostics.Debug.WriteLine("User name: "
				+ jsonResult["from_user"].ToString());
	System.Diagnostics.Debug.WriteLine("Language: "
				+ jsonResult["iso_language_code"].ToString())

}

Obviously in production code you’d want to be a bit more careful than the test sample above (for example using GetType() to validate each step), but hopefully that gives you some insight into parsing Twitter’s JSON into C#. Once you’ve got your head around the Hashtable > ArrayList > Hashtable structure its actually very quick to use.