Скачать или смотреть Ways to Make Property Code-Generated Only in C# Using Entity Framework

Discover how to create abstract classes in C# that restrict user modifications to properties, ensuring they are only updated through code, using Entity Framework and C# 9.0 features.
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This video is based on the question https://stackoverflow.com/q/65450688/ asked by the user 'Omelian Levkovych' ( https://stackoverflow.com/u/7642122/ ) and on the answer https://stackoverflow.com/a/65450795/ provided by the user 'jjxtra' ( https://stackoverflow.com/u/56079/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Make Property Code-Generated Only in C# with Entity Framework

If you are a .NET Core developer using Entity Framework, you might have come across a scenario where you need to create an abstract class containing properties that should remain unchanged by user input. You want these properties to be code-generated only, meaning they can only be set programmatically when you create or update entities. A common requirement is ensuring certain properties, like creation timestamps or last active dates, are automatically managed without external interference. This guide will explore how to achieve this by leveraging the power of C# 9.0's initonly properties.

The Problem

You want to define an abstract class—let's call it SystemEntityBase—that maintains properties such as Created and LastActive. You want these properties to be read-only for any consumer of the class. However, the challenge lies in using read-only properties with Entity Framework (EF) Core, as they won't be included in the database schema when generating migrations due to their immutable nature.

Here's a simplified version of what you are trying to accomplish:

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While this structure ensures that the properties can't be modified after initialization, it poses an issue for Entity Framework—these properties will not appear in your database.

The Solution: Using init Only Properties

Fortunately, there's a more flexible solution introduced in C# 9.0: init only properties. This feature allows you to define properties that can only be set during object initialization, making it possible to retain the immutability you desire while also allowing Entity Framework to map these properties to database columns.

Key Benefits of init Properties

Immutability: They cannot be changed after the object is constructed.

Entity Framework Compatibility: Since these properties can be assigned during initialization, they will be considered for database mapping.

Implementing init Properties

Here’s how you can redefine your abstract class using init properties:

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In this updated version:

The Created and LastActive properties are defined with the init accessor, meaning they can be set when the object is created but are read-only thereafter.

These properties will be included in the Entity Framework migrations, allowing them to be persisted in the database.

Example Usage

When you create a subclass that inherits from SystemEntityBase, you can initialize these properties directly when instantiating the object:

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

Summary

By making use of init only properties in C# 9.0, you can effectively design your entities to maintain read-only characteristics while still leveraging Entity Framework's capabilities to manage your database schema. Not only does this approach cleanly solve your problem, but it also opens up new possibilities for maintaining consistent state and enforcing business rules throughout your application.

This method ensures that critical properties in your entities remain strictly controlled by your code, preventing unwanted changes—keeping your application robust and reliable.