DbContextOptions 是如何被注入的？

Question

I saw a lot of code like this below:

public class EFCoreContext : DbContext 
{
    public EFCoreContext(DbContextOptions<EFCoreContext> options) : base(options) { }

    public DbSet<Book> Books { get; set; }
    ...
}

So I think DbContextOptions<EFCoreContext> options is injected by DI via:

// Startup.cs
public void ConfigureServices(IServiceCollection services) 
{
    services.AddDbContext<EFCoreContext>(   // register EFCoreContext so it can be injected
        options => options.UseSqlServer(connection)   // tell EF that you're using an SQL Server database by using the UseSqlServer method
    ); 
}

But I checked the source code ( https://github.com/dotnet/efcore/blob/main/src/EFCore/Extensions/EntityFrameworkServiceCollectionExtensions.cs ) of AddDbContext, I couldn't find any code related to the injection of DbContextOptions<EFCoreContext> .

I have two questions:

1. How does it get injected?

2. Why do we need to have public EFCoreContext(DbContextOptions<EFCoreContext> options) : base(options) { } ? It looks like this piece of code just tells EF that we will be using EFCoreContext , as DbContext, but we have already register EFCoreContext in startup.cs, any class's constructor takes a EFCoreContext will work, isn't it?

Answer 1

1. You can inject your dbcontext on any class or any contoller like the below:

   Public class YourService{

   private readonly EFCoreContext _dbContext; constructor(EFCoreContext dbContext) _dbContext= dbContext; }

2. The base option is used to override the default behavior of ef core dbcontext class. But you can do the same on the startup class also.