C# Entity Framework DBContext

Question

I am trying to learn Code First EF6 and I am confused regarding DBContext.

The database I will be working on contains 800+ tables, while when working of specific parts of the application I am only dealing with 1-10 tables.

So my question is; would not having a DBContext involving 800+ Classes have a big negative impact on system resources?

I guess I am new to this technology and confused regarding the actual meaning of the information that I am taking in during my research.

Thank you.

NOTE: Thank you for your inputs. Please take a look at this post: Using multiple DbContexts with a generic repository and unit of work. There it states I cannot have tables in separate contexts that relate to each other?!

But in a real world scenerio my understanding is that it is common to break up the table relationships in focused areas, how is this done in Code First EF? Thanks again.

Answer 1

Updated

If you are using Repository Pattern, you cannot go make multiple DbContext, You Create One Generic, And pass it to your Generic Repository like below :

public class Repository<T> : IRepository<T>
    where T : EntityBase
{
    internal MyDbContext context;
    internal DbSet<T> dbSet; 

    public Repository()
    {
        context = new MyDbContext();
        this.dbSet = context.Set<T>(); 
    }
    public void Add(T entity)
    {
        dbSet.Add(entity);
    }
    public void Delete(T entity)
    {
        dbSet.Remove(entity);
    }
    public void Delete(int id)
    {
        dbSet.Remove(dbSet.Find(id));
    }
    public T GetById(int id)
    {
        return dbSet.Find(id);
    }
    public IEnumerable<T> GetAll()
    {
        return dbSet.AsEnumerable();
    }
    public void Update(T entity)
    {
        dbSet.Attach(entity);
        context.Entry(entity).State = EntityState.Modified;
    }
    public void Save()
    {
        context.SaveChanges(); 
    }
}

And you should include your DbSets there as well.

---

If you are doing EF Code-First then its yours to design your POCO class based on how many are needed but no more. But based on what you said about 800 tables i think you may want to try Database-First Approach rather. i suggest you this article very carefully as it explain everything you need.

Update:

If you Approach this from DataBase-First: Ado.NET Entity Model Creates your DbContext for you! If you take a closer look at the .Edmx file it is basically your POCO Classes within.

Now if you try Code-First Approach, lets say you have this DbContext Class:

public class MyDbContext : DbContext
{
    public MyDbContext()
        : base("name=MyConnection")
    {
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<MyDbContext, YourApplication.Migrations.Configuration>("MyConnection")); 
    }
    //Every time you need to add new Table you add them here.
    public DbSet<Users> Users { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        //And Map them here
        modelBuilder.Configurations.Add(new UsersMap());
    }
}

You just add a new DbSet<Class> to your DbContext like below:

    public DbSet<POCO CLASS> CLASS { get; set; }

And so on, i normally create a DbContext for Every Area i have in my MVC Application. So you can go like Admin Area -> AdminDbContext And so on.

Answer 2

You only need the tables you are working with in your db context (if the db already exists). The only reason you'd need a db context with all the tables would be if you want to recreate the whole db from scratch.

Take a look at the bounded context pattern from DDD: http://martinfowler.com/bliki/BoundedContext.html