首先将可更新视图与实体框架代码一起使用

Question

I am learning to use Entity Framework (code first). Everything was going well until I realized I need to interact with an existing updatable view. I have confirmed the view can be updated in SSMS.

There are two entities involved: AppUser (Identity User) and FacilityView.

public class AppUser : IdentityUser
{        
    // additional props
    public virtual ICollection<FacilityView> Facilities { get; set; }
}

public class FacilityView
{
    [HiddenInput(DisplayValue=false)]
    public int ID { get; set; }
    public string Name { get; set; }
    public string County { get; set; }
    public string WebSiteURL { get; set; }
    public bool IsActive { get; set; }

    public virtual ICollection<AppUser> Users { get; set; }
}

I've used navigation properties to relate the two, thinking EF will build the join table when I run the next migration. I've read that EF treats views as read-only, so I tried to override this by creating my own EntityTypeConfiguration class:

public class FacilityViewConfiguration : EntityTypeConfiguration<FacilityView>
{
    public FacilityViewConfiguration()
    {
        this.HasKey(t => t.ID);
        this.ToTable("FacilityViews");
    }
}

The configuration is referenced in my context class inside the OnModelCreating method.

public class AppIdentityDbContext : IdentityDbContext<AppUser>
{
    public AppIdentityDbContext() : base("DbConn") { }

    public DbSet<Facility> Facilities { get; set; }
    public DbSet<FacilityView> FacilityDetails { get; set; }        

    static AppIdentityDbContext()
    {
        Database.SetInitializer<AppIdentityDbContext>(new DbConnInit());
    }

    public static AppIdentityDbContext Create()
    {
        return new AppIdentityDbContext();
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {

        base.OnModelCreating(modelBuilder);

        // TRYING TO TRICK EF HERE
        modelBuilder.Configurations.Add(new FacilityViewConfiguration());           
    }
}  

When I add a migration, this is the resulting Up and Down:

public partial class UserFacilityJoinTable : DbMigration
{
    public override void Up()
    {
        CreateTable(
            "dbo.AppUserFacilityViews",
            c => new
                {
                    AppUser_ID = c.String(nullable: false, maxLength: 128),
                    FacilityViewsID = c.Int(nullable: false),
                })
            .PrimaryKey(t => new { t.AppUser_ID, t.FacilityViewsID })
            .ForeignKey("dbo.AspNetUsers", t => t.AppUser_ID, cascadeDelete: true)
            .ForeignKey("dbo.FacilityViews", t => t.FacilityViewsID, cascadeDelete: true)
            .Index(t => t.AppUser_ID)
            .Index(t => t.FacilityViewsID);

    }

    public override void Down()
    {
        DropForeignKey("dbo.AppUserFacilityViews", "FacilityViewsID", "dbo.FacilityViews");
        DropForeignKey("dbo.AppUserFacilityViews", "AppUser_ID", "dbo.AspNetUsers");
        DropIndex("dbo.AppUserFacilityViews", new[] { "FacilityViewsID" });
        DropIndex("dbo.AppUserFacilityViews", new[] { "AppUser_ID" });
        DropTable("dbo.AppUserFacilityViews");
    }
}

It is attempting to create a new join table like I wanted, but when I run the Update-Database command, I get the following error:

Foreign key 'FK_dbo.AppUserFacilityViews_dbo.FacilityViews_FacilityViewsID' references object 'dbo.FacilityViews' which is not a user table. Could not create constraint. See previous errors.

I thought I had tricked EF into treating the view like a table, but it's obviously not buying it. I'm wondering if I missed something or maybe taking the wrong approach. Any help will be greatly appreciated. I've been stuck here for a few days.

Answer 1

AFAIK you can't create a constraint to/from a view (even a materialized one, exception of index).

But you can model your context without database FK. You then have to handle the integrity at context or application level