C# – Convert an object to JSON and vice versa

The simplest way to convert an object to JSON (serialization) is to use the built-in System.Text.Json.JsonSerializer:

using System.Text.Json;

var movie = new Movie()
{
	Title = "A Quiet Place Part II",
	RuntimeMinutes = 97,
	ImdbRating = 7.3m,
	ReleaseDate = new DateTime(year: 2021, month: 5, day: 28),
	OnlyReleasedInTheatres = false
};

var json = JsonSerializer.Serialize(movie);

Code language: C# (cs)

This serializes the Movie object to JSON using the default serialization settings (notice it’s not pretty printed by defualt). Here’s the JSON this produces:

{"Title":"A Quiet Place Part II","RuntimeMinutes":97,"ImdbRating":7.3,"ReleaseDate":"2021-05-28T00:00:00","OnlyReleasedInTheatres":false,"PopcornEaten":null}Code language: JSON / JSON with Comments (json)

To do the opposite – convert a JSON string to an object (deserialization) – use Deserialize<T>():

using System.Text.Json;

var movie = JsonSerializer.Deserialize<Movie>(json);
Code language: C# (cs)

This deserializes the JSON string to a Movie object using the default settings.

JSON serialization settings

You can change the serialization settings by passing in a JsonSerializerOptions object. Reuse the JsonSerializerOptions object to greatly improve performance.

There are many settings. I’ll show a few common ones below. If the settings aren’t getting you what you want, you can also write a custom converter to deal with your specific JSON serialization scenario.

Pretty print

To make the JSON easier for people to read, pretty print it by using WriteIndented=true:

var settings = new JsonSerializerOptions()
{
	WriteIndented = true
};

var json = JsonSerializer.Serialize(movie, settings);
Code language: C# (cs)

This generates the following pretty printed JSON:

{
  "Title": "A Quiet Place Part II",
  "RuntimeMinutes": 97,
  "ImdbRating": 7.3,
  "ReleaseDate": "2021-05-28T00:00:00",
  "OnlyReleasedInTheatres": false,
  "PopcornEaten": null
}Code language: JSON / JSON with Comments (json)

Camel casing

By default, JsonSerializer will read/write property names exactly as they are. In .NET, the convention is to use pascal casing for property names (ex: PropertyName). You can make it use camel casing by setting PropertyNamingPolicy to JsonNamingPolicy.CamelCase:

var settings = new JsonSerializerOptions()
{
	PropertyNamingPolicy = JsonNamingPolicy.CamelCase
};

//generates camel-cased JSON
var json = JsonSerializer.Serialize(movie, settings);

//can handle camel-cased JSON
var newMovie = JsonSerializer.Deserialize<Movie>(json);
Code language: C# (cs)

This allows you to handle JSON with camel-cased property names, like this:

{
  "title": "A Quiet Place Part II",
  "runtimeMinutes": 97,
  "imdbRating": 7.3,
  "releaseDate": "2021-05-28T00:00:00",
  "onlyReleasedInTheatres": false,
  "popcornEaten": null
}Code language: JSON / JSON with Comments (json)

Ignore null properties

If you don’t want the JSON to include null properties (ex: “title”:null), you can make it ignore null properties during serialization by using JsonIgnoreCondition.WhenWritingNull:

var writer = new Writer()
{
	FirstName = "Joanne",
	MiddleName = null,
	LastName = "Rowling",
	PenName = "J.K. Rowling"
};
//Yep, no middle name!

var settings = new JsonSerializerOptions()
{
	DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull
};

var json = JsonSerializer.Serialize(writer, settings);
Code language: C# (cs)

This generates the following JSON. Notice how it doesn’t have the MiddleName property:

{"FirstName":"Joanne","LastName":"Rowling","PenName":"J.K. Rowling"}Code language: JSON / JSON with Comments (json)

Web defaults

You can initialize JsonSerializerOptions with JsonSerializerDefaults.Web (this is what ASP.NET uses). This makes it use the following settings (currently):

• Case insensitive property name matching when deserializing.
• Camel casing when serializing.
• Read quoted numbers when deserializing (ex: “123”).

Here’s an example of using this to serialize:

var settings = new JsonSerializerOptions(JsonSerializerDefaults.Web);
var json = JsonSerializer.Serialize(new Person() { Name = "Bob" }, settings);
Code language: C# (cs)

This generates the following JSON. Notice “name” is camel-cased:

{"name":"Bob"}Code language: JSON / JSON with Comments (json)

Getting System.Text.Json

For .NET Core 3.0 and above, System.Text.Json is included in the framework.

For versions before that, you can install the System.Text.Json package (View > Other Windows > Package Manager Console):

Install-Package System.Text.Json
Code language: PowerShell (powershell)

This is available for versions back to .NET Framework 4.6.1.

Using Newtonsoft.Json

Newtonsoft.Json was the de facto JSON serialization library for several years. Microsoft started developing System.Text.Json as a long-term replacement for Newtonsoft.Json. If you want to (or have to) use Newtonsoft, here’s a quick introduction.

First, install the Newtonsoft.Json package (View > Other Windows > Package Manager Console):

Install-Package Newtonsoft.Json
Code language: PowerShell (powershell)

To convert an object to JSON (serialization), use JsonConvert.SerializeObject():

using Newtonsoft.Json;

var movie = new Movie()
{
	Title = "A Quiet Place Part II",
	RuntimeMinutes = 97,
	ImdbRating = 7.3m,
	ReleaseDate = new DateTime(year: 2021, month: 5, day: 28),
	OnlyReleasedInTheatres = false,
	PopcornEaten = null
};

var json = JsonConvert.SerializeObject(movie, Formatting.Indented);
Code language: C# (cs)

This generates the following JSON:

{
  "Title": "A Quiet Place Part II",
  "RuntimeMinutes": 97,
  "ImdbRating": 7.3,
  "ReleaseDate": "2021-05-28T00:00:00",
  "OnlyReleasedInTheatres": false,
  "PopcornEaten": null
}Code language: JSON / JSON with Comments (json)

Notice how easy it is to pretty print? Just have to pass in Formatting.Indented instead of needing to pass in a settings object.

To convert JSON to an object (deserialization), use DeserializeObject<T>():

using Newtonsoft.Json;

var newMovie = JsonConvert.DeserializeObject<Movie>(json);
Code language: C# (cs)

You can change the serialization settings by passing in JsonSerializerSettings. For example, this is pretty printing and camel casing the property names:

using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

var settings = new JsonSerializerSettings()
{
	ContractResolver = new CamelCasePropertyNamesContractResolver(),
	Formatting = Formatting.Indented
};

var json = JsonConvert.SerializeObject(new Person() { Name = "Nandor" }, settings);
Code language: C# (cs)

This generates the following JSON:

{
  "name": "Nandor"
}Code language: JSON / JSON with Comments (json)