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

Try using Database SetInitializer which belongs to using System.Data.Entity;

In Global.asax

protected void Application_Start()
{
    Database.SetInitializer(new DropCreateDatabaseIfModelChanges<yourContext>());
}

This will create new database everytime your model is changed.But your database would be empty.In order to fill it with dummy data you can use Seeding. Which you can implement as :

Seeding ::

protected void Application_Start()
{
    Database.SetInitializer(new AddressBookInitializer());
                ----rest code---
}
public class AddressBookInitializer : DropCreateDatabaseIfModelChanges<AddressBook>
{
    protected override void Seed(AddressBook context)
    {
        context.yourmodel.Add(
        {

        });
        base.Seed(context);
    }

}

Answer 2

Create custom context initializer:

public class MyDbContextInitializer : MigrateDatabaseToLatestVersion<MyDbContext, Migrations.Configuration>
{
    public override void InitializeDatabase(MyDbContext context)
    {
        bool exists = context.Database.Exists();

        base.InitializeDatabase(context);

        if (!exists)
        {         
            MyDbSeed.Seed(context);
        }
    }       
}

Note that Migrations.Configuration is a class generating by migration command line in Package Manager Console. You may need to change internal to public modifier of the Migrations.Configuration class.

And register it from your OmModelCreating:

public partial class MyDbContext : DbContext
{

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        Database.SetInitializer<MyDbContext>(new MyDbContextInitializer());

        //other code for creating model
    }
}

Answer 3

I had this issue and it turned out that one project was pointing to SQLExpress but the one with the problem was pointing to LocalDb. (in their respective web.config). Silly oversight but worth noting here in case anyone else is troubleshooting this issue.

Answer 4

It's weird, but all answers here were useless for me. For me worked initializer

MigrateDatabaseToLatestVersion

Here's my solution (I know, it can be much simplier, but it's how I use it):

class MyDbMigrateToLatest : MigrateDatabaseToLatestVersion<MyDbContext, Configuration>
{
}

public class MyDbContext: DbContext
{
    public MyDbContext() : base("DbName")
    {
        SetInitializer();
    }

    public MyDbContext(string connString) : base(connString)
    {
        SetInitializer();
    }

    private static void SetInitializer()
    {
        if (ConfigurationManager.AppSettings["RebuildDatabaseOnStart"] == "true")
            Database.SetInitializer(new MyDbInitializerForTesting());
        else
            Database.SetInitializer(new MyDbMigrateToLatest());
    }
}

public sealed class Configuration : DbMigrationsConfiguration<MyDbContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = true;
    }

    protected override void Seed(MyDbContext context)
    {
        // Whatever
    }
}

MyDbInitializerForTesting just inherits from DropCreateDatabaseAlways so in some specific case (testing), whole database is rebuilded. Otherwise it's migrated to latest version.

My source: https://msdn.microsoft.com/en-us/data/jj591621.aspx#specific

Answer 5

After some research on this topic, I found that the error is occured basically if you have an instance of db created previously on your local sql server express. So whenever you have updates on db and try to update the db/run some code on db without running Update Database command using Package Manager Console; first of all, you have to delete previous db on our local sql express manually.

Also, this solution works unless you have AutomaticMigrationsEnabled = false;in your Configuration.

If you work with a version control system (git,svn,etc.) and some other developers update db objects in production phase then this error rises whenever you update your code base and run the application.

As stated above, there are some solutions for this on code base. However, this is the most practical one for some cases.

Answer 6

None of these solutions would work for us (other than disabling the schema checking altogether). In the end we had a miss-match in our version of Newtonsoft.json

Our AppConfig did not get updated correctly:

<dependentAssembly>
   <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-7.0.0.0" newVersion="7.0.0.0" />
  </dependentAssembly>

The solution was to correct the assembly version to the one we were actually deploying

<dependentAssembly>
   <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-7.0.0.0" newVersion="10.0.0.0" />
  </dependentAssembly>