What is the difference between Serialization and Marshaling?

How to serialize and deserialize JSON using C# - .NET | Microsoft Docs https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-how-to?pivots=dotnet-5-0

This article shows how to use the System.Text.Json namespace to serialize to and deserialize from JavaScript Object Notation (JSON). If you're porting existing code from Newtonsoft.Json, see How to migrate to System.Text.Json.

The directions and sample code use the library directly, not through a framework such as ASP.NET Core.

Most of the serialization sample code sets JsonSerializerOptions.WriteIndented to true to "pretty-print" the JSON (with indentation and whitespace for human readability). For production use, you would typically accept the default value of false for this setting.

The directions and sample code use the library directly, not through a framework such as ASP.NET Core.

The code examples refer to the following class and variants of it:

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public class WeatherForecast
{
    public DateTimeOffset Date { get; set; }
    public int TemperatureCelsius { get; set; }
    public string Summary { get; set; }
}

Namespaces

The System.Text.Json namespace contains all the entry points and the main types. The System.Text.Json.Serialization namespace contains attributes and APIs for advanced scenarios and customization specific to serialization and deserialization. The code examples shown in this article require using directives for one or both of these namespaces:

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using System.Text.Json;
using System.Text.Json.Serialization;

Important

Attributes from the System.Runtime.Serialization namespace aren't supported in System.Text.Json.

How to write .NET objects as JSON (serialize)

To write JSON to a string or to a file, call the JsonSerializer.Serialize method.

The following example creates JSON as a string:

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string jsonString = JsonSerializer.Serialize(weatherForecast);

The following example uses synchronous code to create a JSON file:

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jsonString = JsonSerializer.Serialize(weatherForecast);
File.WriteAllText(fileName, jsonString);

The following example uses asynchronous code to create a JSON file:

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using FileStream createStream = File.Create(fileName);
await JsonSerializer.SerializeAsync(createStream, weatherForecast);

The preceding examples use type inference for the type being serialized. An overload of Serialize() takes a generic type parameter:

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jsonString = JsonSerializer.Serialize<WeatherForecastWithPOCOs>(weatherForecast);

Serialization example

Here's an example class that contains collection-type properties and a user-defined type:

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public class WeatherForecastWithPOCOs
{
    public DateTimeOffset Date { get; set; }
    public int TemperatureCelsius { get; set; }
    public string Summary { get; set; }
    public string SummaryField;
    public IList<DateTimeOffset> DatesAvailable { get; set; }
    public Dictionary<string, HighLowTemps> TemperatureRanges { get; set; }
    public string[] SummaryWords { get; set; }
}

public class HighLowTemps
{
    public int High { get; set; }
    public int Low { get; set; }
}

Tip

"POCO" stands for plain old CLR object. A POCO is a .NET type that doesn't depend on any framework-specific types, for example, through inheritance or attributes.

The JSON output from serializing an instance of the preceding type looks like the following example. The JSON output is minified (whitespace, indentation, and new-line characters are removed) by default:

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{"Date":"2019-08-01T00:00:00-07:00","TemperatureCelsius":25,"Summary":"Hot","DatesAvailable":["2019-08-01T00:00:00-07:00","2019-08-02T00:00:00-07:00"],"TemperatureRanges":{"Cold":{"High":20,"Low":-10},"Hot":{"High":60,"Low":20}},"SummaryWords":["Cool","Windy","Humid"]}

The following example shows the same JSON, but formatted (that is, pretty-printed with whitespace and indentation):

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{
  "Date": "2019-08-01T00:00:00-07:00",
  "TemperatureCelsius": 25,
  "Summary": "Hot",
  "DatesAvailable": [
    "2019-08-01T00:00:00-07:00",
    "2019-08-02T00:00:00-07:00"
  ],
  "TemperatureRanges": {
    "Cold": {
      "High": 20,
      "Low": -10
    },
    "Hot": {
      "High": 60,
      "Low": 20
    }
  },
  "SummaryWords": [
    "Cool",
    "Windy",
    "Humid"
  ]
}

Serialize to UTF-8

To serialize to UTF-8, call the JsonSerializer.SerializeToUtf8Bytes method:

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byte[] jsonUtf8Bytes;
var options = new JsonSerializerOptions
{
    WriteIndented = true
};
jsonUtf8Bytes = JsonSerializer.SerializeToUtf8Bytes(weatherForecast, options);

A Serialize overload that takes a Utf8JsonWriter is also available.

Serializing to UTF-8 is about 5-10% faster than using the string-based methods. The difference is because the bytes (as UTF-8) don't need to be converted to strings (UTF-16).

Serialization behavior

By default, all public properties are serialized. You can specify properties to ignore.
The default encoder escapes non-ASCII characters, HTML-sensitive characters within the ASCII-range, and characters that must be escaped according to the RFC 8259 JSON spec.
By default, JSON is minified. You can pretty-print the JSON.
By default, casing of JSON names matches the .NET names. You can customize JSON name casing.
By default, circular references are detected and exceptions thrown. You can preserve references and handle circular references.
By default, fields are ignored. You can include fields.

When you use System.Text.Json indirectly in an ASP.NET Core app, some default behaviors are different. For more information, see Web defaults for JsonSerializerOptions.

Supported types include:

.NET primitives that map to JavaScript primitives, such as numeric types, strings, and Boolean.
User-defined plain old CLR objects (POCOs).
One-dimensional and jagged arrays (T[][]).
Collections and dictionaries from the following namespaces.

You can implement custom converters to handle additional types or to provide functionality that isn't supported by the built-in converters.

How to read JSON as .NET objects (deserialize)

To deserialize from a string or a file, call the JsonSerializer.Deserialize method.

The following example reads JSON from a string and creates an instance of the WeatherForecastWithPOCOs class shown earlier for the serialization example:

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weatherForecast = JsonSerializer.Deserialize<WeatherForecastWithPOCOs>(jsonString);

To deserialize from a file by using synchronous code, read the file into a string, as shown in the following example:

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jsonString = File.ReadAllText(fileName);
weatherForecast = JsonSerializer.Deserialize<WeatherForecast>(jsonString);

To deserialize from a file by using asynchronous code, call the DeserializeAsync method:

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using FileStream openStream = File.OpenRead(fileName);
weatherForecast = await JsonSerializer.DeserializeAsync<WeatherForecast>(openStream);

Deserialize from UTF-8

To deserialize from UTF-8, call a JsonSerializer.Deserialize overload that takes a ReadOnlySpan<byte> or a Utf8JsonReader, as shown in the following examples. The examples assume the JSON is in a byte array named jsonUtf8Bytes.

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var readOnlySpan = new ReadOnlySpan<byte>(jsonUtf8Bytes);
weatherForecast = JsonSerializer.Deserialize<WeatherForecast>(readOnlySpan);

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var utf8Reader = new Utf8JsonReader(jsonUtf8Bytes);
weatherForecast = JsonSerializer.Deserialize<WeatherForecast>(ref utf8Reader);

Deserialization behavior

The following behaviors apply when deserializing JSON:

By default, property name matching is case-sensitive. You can specify case-insensitivity.
If the JSON contains a value for a read-only property, the value is ignored and no exception is thrown.
Non-public constructors are ignored by the serializer.
Deserialization to immutable objects or read-only properties is supported. See Immutable types and Records.
By default, enums are supported as numbers. You can serialize enum names as strings.
By default, fields are ignored. You can include fields.
By default, comments or trailing commas in the JSON throw exceptions. You can allow comments and trailing commas.
The default maximum depth is 64.

When you use System.Text.Json indirectly in an ASP.NET Core app, some default behaviors are different. For more information, see Web defaults for JsonSerializerOptions.

You can implement custom converters to provide functionality that isn't supported by the built-in converters.

Serialize to formatted JSON

To pretty-print the JSON output, set JsonSerializerOptions.WriteIndented to true:

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var options = new JsonSerializerOptions
{
    WriteIndented = true,
};
jsonString = JsonSerializer.Serialize(weatherForecast, options);

Here's an example type to be serialized and pretty-printed JSON output:

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public class WeatherForecast
{
    public DateTimeOffset Date { get; set; }
    public int TemperatureCelsius { get; set; }
    public string Summary { get; set; }
}

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{
  "Date": "2019-08-01T00:00:00-07:00",
  "TemperatureCelsius": 25,
  "Summary": "Hot"
}

Include fields

Use the JsonSerializerOptions.IncludeFields global setting or the [JsonInclude] attribute to include fields when serializing or deserializing, as shown in the following example:

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using System;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Fields
{
    public class Forecast
    {
        public DateTime Date;
        public int TemperatureC;
        public string Summary;
    }

    public class Forecast2
    {
        [JsonInclude]
        public DateTime Date;
        [JsonInclude]
        public int TemperatureC;
        [JsonInclude]
        public string Summary;
    }

    public class Program
    {
        public static void Main()
        {
            var json =
                @"{""Date"":""2020-09-06T11:31:01.923395-07:00"",""TemperatureC"":-1,""Summary"":""Cold""} ";
            Console.WriteLine($"Input JSON: {json}");

            var options = new JsonSerializerOptions
            {
                IncludeFields = true,
            };
            var forecast = JsonSerializer.Deserialize<Forecast>(json, options);

            Console.WriteLine($"forecast.Date: {forecast.Date}");
            Console.WriteLine($"forecast.TemperatureC: {forecast.TemperatureC}");
            Console.WriteLine($"forecast.Summary: {forecast.Summary}");

            var roundTrippedJson =
                JsonSerializer.Serialize<Forecast>(forecast, options);

            Console.WriteLine($"Output JSON: {roundTrippedJson}");

            options = new JsonSerializerOptions(JsonSerializerDefaults.Web);
            var forecast2 = JsonSerializer.Deserialize<Forecast2>(json);

            Console.WriteLine($"forecast2.Date: {forecast2.Date}");
            Console.WriteLine($"forecast2.TemperatureC: {forecast2.TemperatureC}");
            Console.WriteLine($"forecast2.Summary: {forecast2.Summary}");

            roundTrippedJson =
                JsonSerializer.Serialize<Forecast2>(forecast2, options);
            
            Console.WriteLine($"Output JSON: {roundTrippedJson}");
        }
    }
}

// Produces output like the following example:
//
//Input JSON: { "date":"2020-09-06T11:31:01.923395-07:00","temperatureC":-1,"summary":"Cold"}
//forecast.Date: 9/6/2020 11:31:01 AM
//forecast.TemperatureC: -1
//forecast.Summary: Cold
//Output JSON: { "date":"2020-09-06T11:31:01.923395-07:00","temperatureC":-1,"summary":"Cold"}
//forecast2.Date: 9/6/2020 11:31:01 AM
//forecast2.TemperatureC: -1
//forecast2.Summary: Cold
//Output JSON: { "date":"2020-09-06T11:31:01.923395-07:00","temperatureC":-1,"summary":"Cold"}

To ignore read-only fields, use the JsonSerializerOptions.IgnoreReadOnlyFields global setting.

HttpClient and HttpContent extension methods

Serializing and deserializing JSON payloads from the network are common operations. Extension methods on HttpClient and HttpContent let you do these operations in a single line of code. These extension methods use web defaults for JsonSerializerOptions.

The following example illustrates use of HttpClientJsonExtensions.GetFromJsonAsync and HttpClientJsonExtensions.PostAsJsonAsync:

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using System;
using System.Net.Http;
using System.Net.Http.Json;
using System.Threading.Tasks;

namespace HttpClientExtensionMethods
{
    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Username { get; set; }
        public string Email { get; set; }
    }

    public class Program
    {
        public static async Task Main()
        {
            using HttpClient client = new()
            {
                BaseAddress = new Uri("https://jsonplaceholder.typicode.com")
            };

            // Get the user information.
            User user = await client.GetFromJsonAsync<User>("users/1");
            Console.WriteLine($"Id: {user.Id}");
            Console.WriteLine($"Name: {user.Name}");
            Console.WriteLine($"Username: {user.Username}");
            Console.WriteLine($"Email: {user.Email}");

            // Post a new user.
            HttpResponseMessage response = await client.PostAsJsonAsync("users", user);
            Console.WriteLine(
                $"{(response.IsSuccessStatusCode ? "Success" : "Error")} - {response.StatusCode}");
        }
    }
}

// Produces output like the following example but with different names:
//
//Id: 1
//Name: Tyler King
//Username: Tyler
//Email: Tyler @contoso.com
//Success - Created

There are also extension methods for System.Text.Json on HttpContent.

What is the difference between Serialization and Marshaling?

Namespaces

How to write .NET objects as JSON (serialize)

Serialization example

Serialize to UTF-8

Serialization behavior

How to read JSON as .NET objects (deserialize)

Deserialize from UTF-8

Deserialization behavior

Serialize to formatted JSON

Include fields

HttpClient and HttpContent extension methods

See also

Contents