![]() ![]() Startup project ‘M圜’ targets framework ‘.NETStandard’. You would run into the following error when trying to generate the migration using ‘dotnet-ef migrations add InitialMigration’: The project containing our DbContext is a class library that cannot be run by itself. The command used to generate the migrations needs a project that has a runtime associated. The fact that we added our DbContext in a separate project does make things a little harder here. We need to install a command-line tool to do that: Install dotnet-ef using 'dotnet tool install -global dotnet-ef' It’s time to generate our first migration. Protected override void OnModelCreating(ModelBuilder modelBuilder)Įntity.Property(e => e.TenantId).HasMaxLength(128) Public CatalogDbContext(DbContextOptions options) : base(options) The ones I use here contain the data in my database-per-tenant architecture and make up the Catalog database. Time to add some entities that will represent our database tables. Install them using these commands: dotnet add package Microsoft.EntityFrameworkCoreĭotnet add package ĭotnet add package The second project needs a few NuGet packages. dotnet new webapi -n DatabasePerTenant.WebApiĭotnet new classlib -n Use the following commands to create the two separate projects. That’s what we’re going to do in this example. In most projects, you probably want to split your data layer from your API. TL DR: All code, templates, and pipelines can be found in my repository. Most of what this blog touches can still be used without reading the whole series. This blog is part of a larger series of blogs in which I explain how to set up a database-per-tenant architecture. We will also see how we can deploy those changes in your Azure DevOps pipeline on each release. We will create the models, the DbContext, and the migrations needed to upgrade your database when introducing changes. In this blog, I’ll show you how to get started with EF and Migrations. NET Core API that needs to talk to a database. To assure there are no errors your code must be compilable.Entity Framework could be a logical choice when building a. If you have errors in your code then how could EF properly create the DB model? It would come upon your error not being able to perform its job. Connect to a DB server to base the migrations off an existing catalog, or create a brand new one if it doesn’t exist.Build your code while generating the migrations.I work around this by creating a “dummy” app which only purpose is for me to create the migrations.Ĭircling back to your primary question, EF cannot properly model the database unless it can do the following. This is common, but now you won’t be able to create migrations. This becomes a problem when you split your code up, let’s say you place all data access code in its own solution, away from your app. One unfortunate thing about EF migration creation is that it always must connect to an existing DB server AND it Depends on the existence of an exe in your solution. I have probably confused the heck out of you buy now, but you will soon grow a greater appreciation for this approach as you become friends with Entity Framework. It still needs to build your code and connect to a database server, it will see that the database catalog doesn’t exist yet and it will create the migration code required to create a new DB from nothing, just as you would do in production. To achieve this, delete your existing migrations that the tool created for you, then delete the database table that it maps to and recreate the migration. ![]() What I prefer to do is just keep using one migration because that’s what I want to deploy. As your development progresses you can end up with a handful of migrations with each subsequent one dependent on the prior. You need to be aware that it is going to connect to your DB server and take a snapshot of the existing database and the new migration will only contain the modifications needed to update the existing database. You will probably learn that when you change your code model, EF needs to create a new migration so that it can change the database to match your model. There is one newbie thing that surprises the best of us and I think you should be aware of it. It can create the database for you and it does this with the migrations it creates. It maps a Code model of the database so you don’t have to work directly with SQL commands. ![]() To perform this mapping it needs to build your C# code so that it can determine what the database should look like. It’s focus is to map C# CLR properties and classes to a physical database. To answer that question it’s worth pointing out the primary focus of an object relational mapper (ORM), specifically entity framework the TLDR answer is below. ![]()
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