2

i am working with EF code first. so initially i have no tables in database. so i wrote some class and when query those class then i saw EF code first create those tables in db but when i create sql server view in db and later map that view with my code in c# & EF project and when i try to query that view then i was getting error message as follows.

Additional information: The model backing the 'TestDBContext' context has changed since the database was created. Consider using Code First Migrations to update the database

i understand that EF is telling me to do the migration but if i migrate then EF will create that view in db again when the view is in db already exist.

so tell me how could i inform EF that my view is already is in db so migration is not required. please guide me. thanks

EDIT 1

first time my database has no table. so i wrote some classes like below one.

public class CustomerBase
    {
        public int CustomerID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

        public string Address1 { get; set; }
        public string Address2 { get; set; }

        public string Phone { get; set; }
        public string Fax { get; set; }

    }

    public class Customer : CustomerBase
    {
        public virtual List<Addresses> Addresses { get; set; }
    }

    public class Addresses
    {
        [Key]
        public int AddressID { get; set; }
        public string Address1 { get; set; }
        public string Address2 { get; set; }
        public bool IsDefault { get; set; }
        public virtual List<Contacts> Contacts { get; set; }

        public int CustomerID { get; set; }
        public virtual Customer Customer { get; set; }
    }

    public class Contacts
    {
        [Key]
        public int ContactID { get; set; }

        public string Phone { get; set; }
        public string Fax { get; set; }
        public bool IsDefault { get; set; }

        public int AddressID { get; set; }
        public virtual Addresses Customer { get; set; } 

    }

    public class TestDBContext : DbContext
    {
        public TestDBContext()
            : base("name=TestDBContext")
        {
        }

        public DbSet<Customer> Customer { get; set; }
        public DbSet<Addresses> Addresses { get; set; }
        public DbSet<Contacts> Contacts { get; set; }
    }

when i query the customer like below query then EF create all required tables in db behind the curtains.

var bsCustomer = (from cu in db.Customer
  where (cu.CustomerID == 2)
  select new
  {
      cu,
      Addresses = from ad in cu.Addresses
          where (ad.IsDefault == true)
          from ct in ad.Contacts
          select ad,

  }).ToList();

later i create a view in db and refer that view in code like below one.

public partial class vwCustomer
{
    [Key]
    public int CustomerID { get; set; }

    public string FirstName { get; set; }
}

   public class vwCustomerConfiguration : EntityTypeConfiguration<vwCustomer>
    {
        public vwCustomerConfiguration()
        {
            this.HasKey(t => t.CustomerID);
            this.ToTable("vwCustomers");
        }
    }

so now my DbContext look like below one with view class reference

public class TestDBContext : DbContext
{
    public TestDBContext()
        : base("name=TestDBContext")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new vwCustomerConfiguration());
    }

    public DbSet<Customer> Customer { get; set; }
    public DbSet<Addresses> Addresses { get; set; }
    public DbSet<Contacts> Contacts { get; set; }
    public virtual DbSet<vwCustomer> vwCustomers { get; set; }
}

Error occur the moment i try to query the view

using (var db = new TestDBContext())
{
    var listMyViews = db.vwCustomers.ToList();
}

the error was Additional information: The model backing the 'TestDBContext' context has changed since the database was created. Consider using Code First Migrations to update the database

thanks

Monojit Sarkar
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2 Answers2

2

Another way we can do it and it solve my problem. see the code.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    Database.SetInitializer<YourDbContext>(null);
    base.OnModelCreating(modelBuilder);
}

code taken from here https://stackoverflow.com/a/6143116/6188148

we can follow this approach too.

public partial class AddingvwCustomer : DbMigration
    {
        public override void Up()
        {

        }

        public override void Down()
        {
        }
    }

i guess this will works too but not tested myself.

we can use the Fluent API to configure it using the Ignore method:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Ignore<MyClass>();
}
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Monojit Sarkar
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  • If you would like to use migrations system to update the database schema then with your approach you will encounter problems. If you update your database only manually or with sql scripts then it is perfectly fine. – mr100 Sep 14 '16 at 06:30
  • @mr100 yes your right for first answer or first set of code. i have updated the answer again. – Monojit Sarkar Sep 14 '16 at 08:19
1

Add new migration as normally and from the migration code in Up (and Down) method remove code that tries to create new table manually (call to CreateTable method in Up and DropTable in Down). Then apply migration to your db and everything works perfectly.

Unfortunately automatic migration generation is not very intelligent tool and very often one need to manually specify how the database should be altered. In the documentation for EF migrations it is stated that it is perfectly fine to edit manually migrations code.

mr100
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