Configuring data context

The auto-generated database context (which is presented in the following code) will include:

• Virtual properties of the tables/entities to hold corresponding data.
• The OnConfiguring method, which will configure EF with the database.
• The OnModelCreating method, which will ensure certain constraints and relationships are built while creating the database. It would not be used in our database-first approach as we already have them in place.

The database context should contain the following configuration:

    public partial class MasteringEFCoreDbFirstContext : DbContext
    {
      public virtual DbSet<Blog> Blog { get; set; }
      public virtual DbSet<Post> Post { get; set; }
      protected override void OnConfiguring(DbContextOptionsBuilder
        optionsBuilder)
      {
        if (!optionsBuilder.IsConfigured)
        {
          // Move this connection string to config file later
          ptionsBuilder.UseSqlServer(@"Server=
            (localdb)\mssqllocaldb;Database=MasteringEFCoreDbFirst;
            Trusted_Connection=True;");
          }
      }
      protected override void OnModelCreating(ModelBuilder 
      modelBuilder)
      {
        modelBuilder.Entity<Post>(entity =>
        {
          entity.HasIndex(e => e.BlogId).HasName("IX_Post_BlogId");
          entity.Property(e => e.Title).IsRequired();
          entity.HasOne(d => d.Blog).WithMany(p => p.Post)
            .HasForeignKey(d => d.BlogId);
          });
      }
    }

In case you have noticed the warning, we need to remove the section using dependency injection, which will be performed in the Registering Context in Services (.NET Core DI) section.