Скачать или смотреть Creating a One-to-Many Relationship in EF Core: The Wallet and Transfer Example

Learn how to create a `one-to-many` relationship using Entity Framework Core with a practical example involving Wallet and Transfer entities.
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Creating a One-to-Many Relationship in EF Core: The Wallet and Transfer Example

Building database relationships is a foundational skill in application development. If you're working with Entity Framework Core, understanding how to set up a one-to-many relationship is crucial. This guide will guide you through the process using a real-life example involving two entities: Wallet and Transfer.

The Problem

You have two entities where:

Wallet: Represents a user's wallet that can hold a monetary balance.

Transfer: Represents transactions made using the wallet.

You want to create a mapping where each transfer can be associated with one wallet, but each wallet can have multiple transfers. This results in a classic one-to-many relationship between Wallet and Transfer.

Solution Explanation

To achieve the desired relationship, you will need to:

Add Foreign Key and Navigation Properties

Configure the Mapping in the DbContext

1. Add Foreign Key and Navigation Properties

Let’s start by modifying the Wallet and Transfer classes to include the necessary properties.

Updating the Wallet Class

In Wallet.cs, you need to define a collection of transfers:

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

Updating the Transfer Class

In Transfer.cs, add a foreign key property WalletId and a reference navigation property:

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

2. Configure the Mapping in the DbContext

Next, you need to configure the relationship using the Fluent API. This step is critical to inform EF Core about the one-to-many relationship.

Modify the OnModelCreating Method

In your DbContext, override the OnModelCreating method to set up the relationship:

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

Conclusion

By following the steps above, you successfully set up a one-to-many relationship between your Wallet and Transfer entities in Entity Framework Core. This setup allows you to manage transactions effectively within your application.

Key Takeaways:

Always add foreign keys and navigation properties to the relevant classes.

Use Fluent API to explicitly define relationships in your DbContext.

This approach not only organizes your database but also powers your application's transactional capabilities.

With this guide, you should be able to implement one-to-many mappings in EF Core with confidence. Happy coding!