How to improve JSON deserialization speed in .Net? (JSON.net or other?)

Question

We\'re considering replacing (some or many) \'classic\' SOAP XML WCF calls by JSON (WCF or other) calls, because of the lower overhead and ease of use directly in Javascript

Answer 1

I have spent a little bit more time reading about JSON.NET internals, and my conclusion is that the slowness is caused mostly by reflection.

On the JSON.NET site i have found some nice performance tips, and i tried pretty much everything (JObject.Parse, Custom Converters etc.) but i couldn't squeeze out any significant performance improvement. Then i read the most important note on the whole site:

If performance is important and you don't mind more code to get it then this is your best choice. Read more about using JsonReader/JsonWriter here

So i listened to the advice and i implemented a basic version of a JsonReader to read the string efficiently:

var reader = new JsonTextReader(new StringReader(jsonString));

var response = new GetRoomListResponse();
var currentProperty = string.Empty;

while (reader.Read())
{
    if (reader.Value != null)
    {
        if (reader.TokenType == JsonToken.PropertyName)
            currentProperty = reader.Value.ToString();

        if (reader.TokenType == JsonToken.Integer && currentProperty == "Acknowledge")
            response.Acknowledge = (AcknowledgeType)Int32.Parse(reader.Value.ToString());

        if (reader.TokenType == JsonToken.Integer && currentProperty == "Code")
            response.Code = Int32.Parse(reader.Value.ToString());

        if (reader.TokenType == JsonToken.String && currentProperty == "Message")
            response.Message = reader.Value.ToString();

        if (reader.TokenType == JsonToken.String && currentProperty == "Exception")
            response.Exception = reader.Value.ToString();

        // Process Rooms and other stuff
    }
    else
    {
        // Process tracking the current nested element
    }
}

I think the exercise is clear, and without doubt this is the best performance you can get out of JSON.NET.

Just this limited code is 12x faster than the Deserialize version on my box with 500 rooms, but of course the mapping is not completed. However, i am pretty sure it will be at least 5x faster than deserialization in the worst-case.

Check out this link for more info about the JsonReader and how to use it:

http://james.newtonking.com/json/help/html/ReadingWritingJSON.htm