Database in use error with Entity Framework 4 Code

Question

I have an MVC3 and EF 4 Code First application, which is configured to change the DB when the model changes, by setting the DB Initializer to a DropCreateDatabaseIfModelChanges<TocratesDb>, where TocratesDb is my derived DbContext.

I have now made a change to the model, by adding properties to a class, but when EF tries to drop and recreate the DB, I get the following error:

Cannot drop database "Tocrates" because it is currently in use.

I have absolutely no other connections anywhere open on this database. I assume that my cDbContext still has an open connection to the database, but what can I do about this?

NEW: Now my problem is how to re-create the database based on the model. By using the more general IDatabaseInitializer, I lose that and have to implement it myself.

Answer 1

Your current context must have an opened connection to be able to drop the database. The problem is that there can be other opened connections which will block your db initializer. One very nice example is having opened any table from your database in management studio. Another possible problem can be opened connections in the connection pool of your application.

In MS SQL this can be avoided for example by switching DB to SINGLE USER mode and forcing all connections to be closed and incomplete transactions rolled back:

ALTER DATABASE Tocrates SET SINGLE_USER WITH ROLLBACK IMMEDIATE

You can create a new intializer which will first call this command and then drops the database. Be aware that you should handle a database connection by yourselves because ALTER DATABASE and DROP DATABASE must be called on the same connection.

Edit:

Here you have example using Decorator pattern. You can modify it and initialize inner initializer inside the constructor instead of passing it as a parameter.

public class ForceDeleteInitializer : IDatabaseInitializer<Context>
{
    private readonly IDatabaseInitializer<Context> _initializer;

    public ForceDeleteInitializer(IDatabaseInitializer<Context> innerInitializer)
    {
        _initializer = innerInitializer;    
    }

    public void InitializeDatabase(Context context)
    {
        context.Database.SqlCommand("ALTER DATABASE Tocrates SET SINGLE_USER WITH ROLLBACK IMMEDIATE");
        _initializer.InitializeDatabase(context);
    }
}

Answer 2

I found in EF 6 this fails with an ALTER DATABASE statement not allowed within multi-statement transaction error.

The solution was to use the new transaction behavior overload like this:

context.Database.ExecuteSqlCommand(TransactionalBehavior.DoNotEnsureTransaction, "ALTER DATABASE [" + context.Database.Connection.Database + "] SET SINGLE_USER WITH ROLLBACK IMMEDIATE");

Answer 3

In Visual Studio 2012, the SQL Server Object Explorer window can hold a connection to the database. Closing the window and all windows opened from it releases the connection.

Answer 4

A simple closing of my whole project and reopening it did the trick for me. It's the easiest way to make sure there are no connections still open

Answer 5

I had the same issue.

I resolved it by closing a connection open under the Server Explorer view of Visual Studio.

Answer 6

I realize this is dated but I couldn't get the accepted solution working so I rolled a quick solution...

using System;
using System.Data.Entity;

namespace YourCompany.EntityFramework
{
    public class DropDatabaseInitializer<T> : IDatabaseInitializer<T> where T : DbContext, new()
    {
        public DropDatabaseInitializer(Action<T> seed = null)
        {
            Seed = seed ?? delegate {};
        }

        public Action<T> Seed { get; set; }

        public void InitializeDatabase(T context)
        {
            if (context.Database.Exists())
            {
                context.Database.ExecuteSqlCommand("ALTER DATABASE [" + context.Database.Connection.Database + "] SET SINGLE_USER WITH ROLLBACK IMMEDIATE");
                context.Database.ExecuteSqlCommand("USE master DROP DATABASE [" + context.Database.Connection.Database + "]");
            }

            context.Database.Create();

            Seed(context);
        }
    }
}

This works for me and supports seeding easily.