New in .NET 8.0 (29): Improvements to the JSON source generator

System.Text.Json In the standard version, JSON is mapped to .NET objects using runtime code generation. This has existed since version 6.0 System.Text.Json Also a source generator. It generates mapping code at development time, so that no runtime code generation is necessary. The JSON source generator was (and is) an important tool for performance optimization.

Advertisement

However, with the expansion of the native AOT compiler to ASP.NET Core Web API, this has become even more important, since runtime compilation is not possible with native AOT.

Provides JSON source generator System.Text.Json Version 8.0 contains the following new options:

AWS: Lots of Excel tables in companies – GenAI applications can help

• Source generator for JSON (Text.Json.SourceGeneration.JsonSourceGenerator) now also supports init-only properties introduced in C# 9.0 and required properties introduced in C# 11.0.
• Developers can ensure this through the project settings System.Text.Json Runtime code generation no longer runs at all: false
• Developers can use a static member in program code to ask whether runtime code generation is possible: IsReflectionEnabledByDefault
• Regarding innovations in System.Text.Json 8.0 includes that annotation too (JsonSourceGenerationOptions) Now offers all the options that Classroom does JsonSerializerOptions When programming is a must with class Text.Json. JsonSerializer allowed.

If runtime code generation is turned off in the JSON serializer, but you still try to serialize without a source generator (for example) JsonSerializer.Serialize(new { value = 42 });), you receive the following error message: “Reflection-based serialization has been disabled for this application. Either use the source generator API or explicitly configure the ‘JsonSerializerOptions.TypeInfoResolver’ property.”

If runtime code generation is turned off in the JSON serializer, you’ll need to use one of JsonSerializerContext Create derived class through annotation (JsonSerializable) which receives references to the .NET classes to be (de)serialized. Alternatively you can set the settings via (JsonSourceGenerationOptions) Make

Classes used in the following code Consultant And Person The examples from the previous part of the series were already in the code:

(JsonSerializable(typeof(Address)))
(JsonSerializable(typeof(Person))) 
(JsonSerializable(typeof(Consultant)))
(JsonSourceGenerationOptions(PreferredObjectCreationHandling 
 =JsonObjectCreationHandling.Populate))
 
internal partial class PersonJsonContext : JsonSerializerContext
{
}

You then need to specify this class in the serialization options:

var options = new JsonSerializerOptions
{
 TypeInfoResolver = PersonJsonContext.Default
};

The following list shows that System.Text.Json Now a required member that is not filled in during deserialization causes a runtime error in the JSON source generator.

try
{
 var jsonString = """
 {"FULL-NAME":"Holger Schwichtenberg","PERSONAL-WEBSITE":"www.dotnet-doktor.de"}
 """;
 Console.WriteLine("JSON: " + jsonString);
 var obj = JsonSerializer.Deserialize(jsonString, options);
 if (obj != null) CUI.Success(obj.ToString());
}
catch (Exception ex)
{
 CUI.PrintError(ex.Message); // JSON deserialization for type 'NET8Konsole.Consultant' was missing required properties, including the following: ID !!! Vor .NET 8.0 wäre hier in Verbindung mit Source Generator KEIN Laufzeitfehler aufgetreten. ID war = 0
}

(RME)