How to Serialize Derived Classes with JsonSerializer in C#

Описание: Learn how to correctly serialize derived classes in C# using `JsonSerializer` by understanding the issue of type inference and leveraging non-generic overloads for accurate JSON representation.
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This video is based on the question https://stackoverflow.com/q/62498668/ asked by the user 'Cbsch' ( https://stackoverflow.com/u/284407/ ) and on the answer https://stackoverflow.com/a/62498888/ provided by the user 'Heinzi' ( https://stackoverflow.com/u/87698/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Serialization Issue with Base and Derived Classes in C#

When working with serialization in C# , developers often choose to use JsonSerializer to easily convert objects into JSON format. However, a common problem arises when trying to serialize properties of a derived class through a base class method. If you've come across the scenario where only the properties of the base class are being serialized—leaving out the derived properties—you might be frustrated and wondering why this happens. In this guide, we’ll explore this issue and provide a solution to effectively serialize derived class properties.

The Problem Explained

Let’s look at a typical scenario. You have a base class that overrides the ToString() method to convert the object into a JSON string. The intention is to serialize any derived objects as well. However, when you execute your program, you notice that the output only includes the properties defined in the base class, not the properties of the derived class.

In the provided code:

[[See Video to Reveal this Text or Code Snippet]]

When you call JsonSerializer.Serialize(this);, what happens is that due to type inference, this line doesn't serialize the derived class properties as expected. It ends up treating this as an instance of BaseModel instead of the concrete derived type.

The Solution

Use Non-Generic Overload

To solve this issue, you should utilize the non-generic overload of JsonSerializer.Serialize, which allows you to pass both the object and the object's type explicitly. This way, you ensure that the correct type is serialized, capturing all properties from the derived class.

The modified ToString() method should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Code Example

Here’s the complete modified version of your original code:

[[See Video to Reveal this Text or Code Snippet]]

Key Takeaways

Understanding Type Inference: When this is treated as a specific type, the properties of derived classes may not get serialized as expected.

Using the Correct Overload: By leveraging the non-generic overload for serialization, you can pass the actual type of the object, ensuring the full properties are captured.

Testing and Validation: Run tests after making changes to confirm that the serialization works correctly and that all properties, both from the base and derived classes, are included in the resulting JSON string.

Conclusion

By adopting the suggested approach, you can effectively serialize derived classes in C# , ensuring that all relevant properties are included in your JSON output. This allows for better flexibility and functionality when working with inheritance in object-oriented programming. Happy coding!