Let’s start with a simple JSON string. In most cases, you will get this string from a web service call. For the sake of this tutorial, we will do this manually.
var example1 = @"{""name"":""John Doe"",""age"":20}";
example1 is a simple JSON object with 2 fields: name and age.
In order to access the field(s) in this JSON string, we need to deserialize it into something C# can understand. This is where I would like to introduce the JavaScriptSerializer class, which is part of the System.Web.Script namespace.
var JSONObj = new JavaScriptSerializer().Deserialize<Dictionary<string, string>>(example1);
What this line does is it deserializes the string example1 into an object of type Dictionary<string, string>.
Once we have done that, we can access the fields like this:
JSONObj["name"];
JSONObj["age"];
Note: the Dictionary definition must match the types of the values in our JSON. “John Doe” is a string but 20 is an integer, so we have to use <string, string> and not <string, int>.
Okay, so we have deserialized it but you still have to reference it in a clunky way – object["field_name"] – so let’s fix that!
First, create a class which matches the definition of your JSON. In our case, we need a class with a string property and an int property:
class Example1Model
{
public string name { get; set; }
public int age { get; set; }
}
And now, to deserialize our JSON into an object of that type:
var example1Model = new JavaScriptSerializer().Deserialize<Example1Model>(example1);
And to reference the fields:
example1Model.name;
example1Model.age;
As you can see, this is much cleaner! Your IDE will give you intellisense/auto-completion, type information and everything you would expect from a native type in .NET.
Show me more!
Our first example was great, but it was basic. Now let us handle a complex JSON string — how about a list of orders for a customer?
var example2 = @"{""custId"": 123, ""ordId"": 4567, ""items"":[{""prodId"":1, ""price"":9.99, ""title"":""Product 1""},{""prodId"":78, ""price"":95.99, ""title"":""Product 2""},{""prodId"":1985, ""price"":3.01, ""title"":""Product 3""}] }";
As in example 1, the first thing we need to do is to create your classes, which represent the data in JSON. Here, I created 2 classes — the CustomerOrderSummary is for the outer fields (custId and ordId) and a list of objects of type Item.
class Item
{
public int prodId { get; set; }
public double price { get; set; }
public string title { get; set; }
}
class CustomerOrderSummary
{
public int custId { get; set; }
public int ordId { get; set; }
public List<Item> items { get; set; }
}
And to deserialize the JSON we simply do:
var example2Model = new JavaScriptSerializer().Deserialize<CustomerOrderSummary>(example2);
And to reference the fields:
example2Model.custId;
example2Model.ordId;
example2Model.items.Count;
example2Model.items[0].price
There you have it! You can now parse JSON into .NET objects using C#! If you would like to retrieve and read the JSON via Objective-C and Node.js, feel free to read these two articles: iOS QuickTip: Getting and Reading JSON Data from a URL and How to Use JSON files in Node.js
Other Useful references:
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