Overview

• System.Text.Json creates a JSON contract for each .NET type that determines how it is serialized and deserialized.
• The contract is created based on the shape of the type — its properties, fields and interfaces it implements.
• Types are mapped to contracts either at run time (via reflection) or compile time (via source generation).
• Documentation: https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/custom-contracts

Customizing JSON Contracts

ℹ️ Important

Availability: .NET 7

Modifiers

A modifier is an Action<JsonTypeInfo> or a static void method with a JsonTypeInfo parameter that gets the current state of the contract as an argument and makes modifications to it.

• Modify the JsonTypeInfo.Get property to change serialization behavior
• Modify the JsonTypeInfo.Set property to change deserialization behavior
• Create a new property using JsonTypeInfo.CreateJsonPropertyInfo(Type, String) and add it to the JsonTypeInfo.Properties collection

Modifications

The following modifications can be made:

Process

To customize JSON contracts:

1. Create modifiers
2. Create a JsonSerializerOptions instance
3. In JsonSerializerOptions’s TypeInfoResolver property, set a new DefaultJsonTypeInfoResolver instance
4. In TypeInfoResolver’s Modifiers property, assign custom actions

Example:

JsonSerializerOptions options = new()
{
    TypeInfoResolver = new DefaultJsonTypeInfoResolver
    {
        Modifiers =
        {
            MyCustomModifier1,
            MyCustomModifier2
        }
    }
};