Using Multiple EF Core DbContexts in a Single Application

EF Core is the de facto ORM in the .NET community. To work with EF Core, you create a DbContext, representing your database. However, sometimes, you might need multiple EF Core DbContexts in a single application. In this video, I'll show you when you might need this and how to implement it.

Using Multiple EF Core DbContexts In a Single Application:

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Chapters
0:00 Adding two EF Core DbContext classes
3:57 Registering the DbContexts with DI
4:52 When do you want to use multiple DbContexts?
6:31 Moving DbContexts into separate schemas and creating migrations
10:10 Fixing the EF migration history table schema
11:38 How to use multiple DbContexts in Minimal APIs
15:35 What you can and CAN'T do with multiple DbContexts

[alexmadnix]

I have already used multiple Ef cores, but your lecture is beneficial for me to watch again.

[rustamhajiyev]

Really good one, thanks a lot :) these tips will definitely safe many devs from figuring things out the hard way

[baranacikgoz]

I was coding the base for a modular monolith project, and I saw the notification. Just happiness.

[remyjoseacostamelo]

Oh man, excellent! thanks a lot. 🙏🏾
Can't wait for you to do a video on multitenancy.

[dawidbiell]

Greate video! I am junior software dev and this question came to my mind few weeks ago. Cool explenation and clarify example. Just in time to get rid of my concerns :) Thx

[GlebWritesCode]

I have another use-case - create multiple instances of same DbContext (that use different connection strings) to query different shards of your data (meaning each shard is a separate database) in parallel

[pcostarg]

I would like to see a deep dive into migrations. Specially changes to a production database and how that would work with changes to the schema of a database.

Thanks for all the Awesome videos!

[RobertGaudyn]

My team uses two database contexts. One of the connection strings is configured with the ApplicationIntent=ReadOnly flag. Above these contexts, we have a context manager and it decides which context is to be used depending on the purpose (writing/reading). Both contexts addresses same listener, but connects to different servers: primary (write) and secondary (read).

Hi Milan. Great videos as always! Thanks for your hardwork and high quality videos. Wondering if you can create a video showing your recommendation to avoid downtimes (or minimize it) when deploying changes in the DB schema with Entity Framework. Thanks in advance.

[piotrkowalski]

When using multiple db contexts I recommend using external tools for database migrations like FluentMigrator or DbUp.
It's really easy to get lost in EF migrations. Before you notice you spend most of your time fighting with your models to generate the right migration's code.

Also it's troublesome to migrate all the db contexts before deploying applications in your release pipeline.

[disglaceful]

Great tutorial Milan, I love following your videos. I'm curious, in the case of a modular monolith, the creation of an order would occur in the Orders module which would not have access to the ProductsDbContext. In that instance, how would you access the products needed to create an order? Would the Order module query the Products module using a service abstracted using an interface?

[borisgomiunik]

Nice explanation, thanks. I have it set up very similar. Is there any particular way of joining data from two datacontexts (e.g. showing product names in the order)?

[NagadGames]

🎉 Excellent, I'd like If you can give It a little zoom in on those tiny letters that are hard to read from our side, maybe increasing the environment font size

[zokocx]

Useful content. I nice stuff at the end about drawnbacks and how to use transaction but also you didn't mention that you can use connection from one DbContext in transaction or you can control connection to explicitly through some connection factory.

[yasirmehmood]

Hi Milan, Great Video. I have a question. you did not establish navigation prosperity within LineItems and Product Entities. So how to get Order details with the name of the Product in that order?

[infotips]

I have two contexts in the same assembly, and I also have separate Fluent API configurations in different folders. In the OnModelCreating method, I have to manually ignore the entities from the other context. How can I specify configurations based on the folder path and not the assembly? How should this be handled? Thank you!

[microtech]

Thanks for sharing the information. One thing, what's your opinion on using DBUp vs EF Core Migration?

[MohiyoDeen]

What if I want to use Separate Db per request. Like getting TenantID from Header with each HTTP Request to generate Connection String and then DbContext ?

[liiplima]

Excellent content! One question that remained and I couldn't find anything specific on the internet, making it necessary to relate tables with different contexts, what would it look like? For example: I created a context to deal with all tables related to user inputs and a context to deal with all system calculation tables, but a relationship is made within the DbContext (in the scenario of a single DbContext) to say that input table A is a foreign key in calculation table B. What would it look like in the case of two DbContext?

[michaelsteffen]

I really like the Visual Studio dark theme you are using. Would you share which one it is?