Скачать или смотреть Mastering ASP.NET Core EF Identity: Seeding Country and City Data Without PK Issues

Learn how to effectively seed country and city data in ASP.NET Core EF Identity while maintaining correct relationships without setting primary keys manually.
---
This video is based on the question https://stackoverflow.com/q/66313699/ asked by the user 'Nicolas Lewentorp' ( https://stackoverflow.com/u/10963435/ ) and on the answer https://stackoverflow.com/a/66317245/ provided by the user 'Nicolas Lewentorp' ( https://stackoverflow.com/u/10963435/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: ASP.NET Core EF Identity - Trying to seed city and country data into separate tables, setting PK doesn't work

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Mastering ASP.NET Core EF Identity: Seeding Country and City Data Without PK Issues

When building an application using ASP.NET Core and Entity Framework (EF) Core, one common challenge developers face is properly seeding initial data into the database. This can be especially tricky when dealing with relationships between tables, such as a one-to-many relationship between countries and cities. In this post, we’ll explore a common problem developers encounter when trying to seed this data, and we’ll provide clear guidance on how to solve it.

The Problem

Imagine you’re setting up a database where each country can have multiple cities. To populate this database, you might need to seed initial country and city data. The goal is to create a seamless association between countries and their respective cities. However, an issue arises when you attempt to set primary keys (PKs) manually for your records. If you set the primary keys explicitly, the entries fail to be added to the database, while omitting them leads to auto-incremented IDs, potentially breaking relationship integrity. Here’s a closer look at the original seeding code:

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

This code attempts to manually set the CountryID, which creates complications as the database tries to manage IDs.

The Solution

The key to overcoming this issue lies in understanding how EF Core manages primary keys during the database initialization and migration processes. Below, we’ll break down the solution into simple steps.

Step 1: Remove Explicit PKs

The first step in resolving the issue is to remove any explicit settings of the primary keys in your seeding process. When you leave out the CountryID and CityID, EF Core will automatically handle ID assignments through its built-in functionality.

Updated Code

Here’s how you can modify your original seeding code:

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

Step 2: Trust Auto-Increment Features

By trusting the auto-increment features of EF Core, you ensure that each country and city is assigned a unique identifier, which is crucial for maintaining relationships between your tables. When you add cities related to a country, you simply reference the country's ID that was generated automatically.

Important Considerations

Migration Management: Always run your migrations after making changes to the database schema or seed data. This ensures that your database is updated accordingly.

Consistent Relationships: Always verify that the relationships between tables are established after seeding data, which is easily managed by allowing EF Core to handle ID allocation.

Testing: Test your application thoroughly to ensure that relationships between countries and cities remain intact even as data changes.

Conclusion

Seeding initial data for a one-to-many relationship in ASP.NET Core EF Identity can be a straightforward process if you avoid manually setting primary keys. By allowing EF Core to auto-increment IDs, you not only simplify your code but also ensure that the relationships between your tables are maintained correctly.

Now that you have the proper approach outlined, you can confidently seed your data without worrying about breaking relationships. If you ever find yourself stuck again, remember these steps to efficiently manage your data seeding processes!