The model backing the context has chang

Question

The error message :

"The model backing the 'AddressBook' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the RecreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data."

I am trying to use the code-first feature and following is what I wrote:

var modelBuilder = new ModelBuilder();
var model = modelBuilder.CreateModel();
using (AddressBook context = new AddressBook(model))
{
    var contact = new Contact
    {
        ContactID = 10000,
        FirstName = "Brian",
        LastName = "Lara",
        ModifiedDate = DateTime.Now,
        AddDate = DateTime.Now,
        Title = "Mr."

    };
    context.contacts.Add(contact);
    int result = context.SaveChanges();
    Console.WriteLine("Result :- "+ result.ToString());
}

The context class:

public class AddressBook : DbContext
{
    public AddressBook()
    { }
    public AddressBook(DbModel AddressBook)
        : base(AddressBook)
    {

    }
    public DbSet<Contact> contacts { get; set; }
    public DbSet<Address> Addresses { get; set; }
}

and the connection string:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <connectionStrings>
    <add name="AddressBook" providerName="System.Data.SqlClient"  
         connectionString="Data Source=MyMachine;Initial Catalog=AddressBook;
         Integrated Security=True;MultipleActiveResultSets=True;"/>
    </connectionStrings>
</configuration>

So, the database name is "AddressBook" and the error happens when I trying to add the contact object to the context. Am I missing anything here?

Answer 1

For VB.NET developers:

Add the following line to the Glabal.asax.vb file, at the end of method Application_Start()

Database.SetInitializer(Of ApplicationDbContext)(Nothing)

Change ApplicationDbContext to your specific Db context.

Answer 2

Here I want to share another method that prevent the error of model backing when context changed is:

1) Open your DbContext File

2) Add namespace using Microsoft.AspNet.Identity.EntityFramework;

3) public MyDbContext() : base("name=MyDbContext") { Database.SetInitializer(new DropCreateDatabaseAlways()); }

Answer 3

Just run the followng sql command in SQL Server Management Studio:

delete FROM [dbo].[__MigrationHistory]

Answer 4

For me, with the upgrade to 4.3.1, I just truncate the EdmMetaData table or just delete it outright.

Answer 5

It means that there were some changes on the context which have not been executed. Please run Add-Migration first to generate the changes that we have done (the changes that we might not aware) And then run Update-Database

Answer 6

For Entity Framework 5.0.0.0 - 6.1.3

You DO indeed want to do the following:

1. using System.Data.Entity;   to startup file (console app --> Program.cs / mvc --> global.asax
2. Database.SetInitializer<YourDatabaseContext>(null);

Yes, Matt Frear is correct. UPDATE -EDIT: Caveat is that I agree with others in that instead of adding this code to global.asax added to your DbContext class

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // other code 
    Database.SetInitializer<YOURContext>(null);
    // more code
}

As others mentioned this also is good for handling the unit testing.

Currently I am using this with Entity Framework 6.1.3 /.net 4.6.1