How to Optimize Json.NET Serialization Performance

Newtonsoft is a pretty fast JSON serializer, but you can make it even faster!

By default, JsonConvert uses reflection to recursively search through the structure of an object during the serialization process. By implementing a custom JsonConverter that already knows the exact structure of the object, you can significantly increase serialization performance.

How much faster? That depends! The more complicated the data structure, the larger the performance gain. Below is a simple example...

Action	Method	Milliseconds	Performance Increase
Serialize	Standard	1134	115.59%
	Custom	526
Deserialize	Standard	1488	62.98%
	Custom	913

Deserialize Abstract Classes with Json.NET

Here is a fun problem: how do you deserialize an array of objects with different types, but all of which inherit from the same super class?

If you are using Newtonsoft's Json.NET, then this is actually rather easy to implement!

Example

Here are three classes...

public abstract class Pet { public string Name { get; set; } }

public class Dog : Pet { public string FavoriteToy { get; set; } }

public class Cat : Pet { public bool WantsToKillYou { get; set; } }

...here is an array with instances of those objects mixed together...

new Pet[]

{

    new Cat { Name = "Sql", WantsToKillYou = true },

    new Cat { Name = "Linq", WantsToKillYou = false },

    new Dog { Name = "Taboo", FavoriteToy = "Sql" }

}

...and now let's make it serialize and deseriailze! :)

Extending the JsonConverter

This tactic is actually quite simple! You need to extend a JsonConverter for your specific super class that is able to somehow uniquely identify each child class. In this example we look for a specific property that only exists on the child class, and Newtonsoft's JObjects and JTokens make this very easy to do!