Support updatable views

[AndriySvyryd]

Split off #17270

Would be configured using something like .ToView(updatable: true) and would be used instead of the configured table for CUD operations.

[pfdsilva]

@AndriySvyryd @ajcvickers @JeremyLikness
Please could you confirm if updating of rows is not supported when an entity class is mapped to a view using fluent API?

I have the following code in my OnModelCreating method.

 modelBuilder.Entity<BlogsView>(entity =>
            {
                entity.ToView("BLOGS_VIEW");

                entity.Property(e => e.Id)
                    .HasColumnName("ID")
                    .HasColumnType("NUMBER(38)");

                entity.Property(e => e.Sub)
                    .HasColumnName("SUB")
                    .HasColumnType("VARCHAR2(30)");
            });

When I execute the following code from my Main method, I am noticing that the changes are getting successfully reflected on the database. I was expecting that the update will not go through because I thought updating of views from EFCORE is not supported. May be I have not understood the scope of this github issue. Please could you help me understand?

var entity = db.BlogsView.FirstOrDefault(item => item.Id == 10);

          // Validate entity is not null
          if (entity != null)
          {
            // Make changes on entity
            entity.Id = 10;
            entity.Sub = "new sub";
          }

I am using an Oracle DB and the view that I have created on the DB has a primary key constraint on the Id column of the view.

Other Info:
I am using Microsoft.EntityFrameworkCore (3.1.5) and Microsoft.EntityFrameworkCore.Relational (3.1.5)

[AndriySvyryd]

@pfdsilva In 3.1.5 SaveChanges doesn't differentiate between views and tables, so it will try to update whatever is configured. In 5.0 you'll be able to map an entity type to both a view and a table and SaveChanges will only use the table mapping

[johnwc]

@AndriySvyryd When using scaffolding, there is no way to tell it to use ToTable(...) instead of ToView(...) What do we do in that scenario?

[ErikEJ]

@johnwc You may be able to set it ToTable and specify a Key in a partial class that implements the OnModelCreatingPartial method