Deserialize json array stream one item at a time

c#, json, json.net, serialization, stream

Solution

In order to read the JSON incrementally, you'll need to use a `JsonTextReader` in combination with a `StreamReader`. But, you don't necessarily have to read all the JSON manually from the reader. You should be able to leverage the Linq-To-JSON API to load each large object from the reader so that you can work with it more easily.

For a simple example, say I had a JSON file that looked like this:

[
  {
    "name": "foo",
    "id": 1
  },
  {
    "name": "bar",
    "id": 2
  },
  {
    "name": "baz",
    "id": 3
  }
]

Code to read it incrementally from the file might look something like the following. (In your case you would replace the FileStream with your response stream.)

using (FileStream fs = new FileStream(@"C:\temp\data.json", FileMode.Open, FileAccess.Read))
using (StreamReader sr = new StreamReader(fs))
using (JsonTextReader reader = new JsonTextReader(sr))
{
    while (reader.Read())
    {
        if (reader.TokenType == JsonToken.StartObject)
        {
            // Load each object from the stream and do something with it
            JObject obj = JObject.Load(reader);
            Console.WriteLine(obj["id"] + " - " + obj["name"]);
        }
    }
}

Output of the above would look like this:

1 - foo
2 - bar
3 - baz

Problem

I serialize an array of large objects to a json http response stream. Now I want to deserialize these objects from the stream one at a time. Are there any c# libraries that will let me do this? I've looked at json.net but it seems I'd have to deserialize the complete array of objects at once. ``` [{large json object},{large json object}.....] ``` Clarification: I want to read one json object from the stream at a time and deserialize it.

Original source