Why is EF4 trying to re-create my database even though the model hasn't changed?

Question

I have an ASP.NET MVC 3 Beta website using SQL Server CE 4.0. With both ScottGu's NerdDinner example and my own code, I will sometimes get the following exception as soon as I try to access the database:

File already exists. Try using a different database name. 
[ File name = D:\Sourcecode\NerdDinner\NerdDinner\App_Data\NerdDinners.sdf ]

Line 17:         public ActionResult Index()
Line 18:         {
Line 19:             var dinners = from d in nerdDinners.Dinners
Line 20:                           where d.EventDate > DateTime.Now
Line 21:                           select d;

[SqlCeException (0x80004005): File already exists. Try using a different database name. [ File name = D:\Sourcecode\NerdDinner\NerdDinner\App_Data\NerdDinners.sdf ]]
   System.Data.SqlServerCe.SqlCeEngine.ProcessResults(IntPtr pError, Int32 hr) +92
   System.Data.SqlServerCe.SqlCeEngine.CreateDatabase() +1584
   System.Data.SqlServerCe.SqlCeProviderServices.DbCreateDatabase(DbConnection connection, Nullable`1 timeOut, StoreItemCollection storeItemCollection) +287
   System.Data.Objects.ObjectContext.CreateDatabase() +84
   System.Data.Entity.Internal.DatabaseOperations.Create(ObjectContext objectContext) +35
   System.Data.Entity.Infrastructure.Database.Create() +70
   System.Data.Entity.Infrastructure.CreateDatabaseOnlyIfNotExists`1.InitializeDatabase(TContext context) +360
   System.Data.Entity.Infrastructure.Database.Initialize() +272
   System.Data.Entity.Internal.InternalContext.Initialize() +90
   System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) +34
   System.Data.Entity.Internal.Linq.EfInternalQuery`1.Initialize() +140
   System.Data.Entity.Internal.Linq.EfInternalQuery`1.get_Provider() +29
   System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider() +34
   System.Linq.Queryable.Where(IQueryable`1 source, Expression`1 predicate) +63
   NerdDinner.Controllers.HomeController.Index() in D:\Sourcecode\NerdDinner\NerdDinner\Controllers\HomeController.cs:19

I cannot figure out why this works sometimes with an existing .dbf file and other times it complains. I have even tried explicitly setting the default behaviour with

Database.SetInitializer(new CreateDatabaseOnlyIfNotExists<...>());

Has anyone else experienced this?

• Restarting Cassini doesn't seem to make a difference.
• Hitting refresh in IE after receiving this error will make the exact same page load properly.

Answer 1

Sorry to resurrect such an old question, but I was experiencing this today and have found a workaround which does not involve installing an older version of the CTP.

From The correct url for the blogpost is http://www.hanselman.com/blog/PDC10BuildingABlogWithMicrosoftUnnamedPackageOfWebLove.aspx (about half-way through the blog post)

*Go into your AppStart_SQLCEEntityFramework.cs file and the DefaultConnectionFactory line to this:*

Database.DefaultConnectionFactory = new SqlCeConnectionFactory( 
    "System.Data.SqlServerCe.4.0", 
    HostingEnvironment.MapPath("~/App_Data/"),"");

My particular database is placed in the App_Data folder but I'm assuming that if yours is not you should be able to change the path to suit and it will work.

Hope this helps!

Answer 2

It looks like this is a recently discovered bug. MSDN Forum

The workaround is to re-install SQL Server CE 4.0 CTP 1 download