How to explicitly name the database when using Ent

问题:

I've recently started using Entity Framework migrations and noticed that the database name is not pulling through for me when I run the Update-Database command.

My connectionstring is:

<connectionStrings>
<add name="DataContext" connectionString="Server=.\SQLEXPRESS;Initial Catalog=TestDB;Trusted_Connection=Yes;" providerName="System.Data.SqlClient" />
</connectionStrings>

The very first time I run Update-Database my database is created with the correct name TestDB. However, as soon as I make a change to one of my entities it will not update any longer for me unless I add a Start Up Project Name (I'm using a multi project solution):

Update-Database -StartUpProjectName "TestDB.Data"

This then makes another new database which migrations will always continue to use. I don't mind having to put in the StartUpProjectName command but is there a way to override the default name for the database this produces? It always creates the database as

TestDB.Data.DataContext

Is there a way to ensure that the database created when passing the StartUpProject name is just called TestDB or is this a limitation of using the StartUpProjectName setting?

As a note, I think the reason I need to specify the StartUpProjectName is that I have a multilayer project setup. The Migrations Configuration file is in my 'Data' project, the entities/models are in my 'Domain' project, etc. I also do not currently have any initialize options in my Global.asax.cs file as I would have used previously on code first ef 4.2. So in my project I just have a DataContext in my Data project and the Migrations Configuration in that project also.

EDIT:

Since I originally setup this question I stumbled onto the 'correct' way to name a database in a multiproject solution. While the answer below will work it does mean you are duplicating your web.config in another area which isn't an ideal solution. Instead you can just put the name into your DbContext by doing something like this (DataContext is just the name I used in my project):

public class DataContext : DbContext
{
    public DataContext() : base("DatabaseNameHere")
    { }

    public DbSet<Table1> Table1 { get; set; }
    public DbSet<Table2> Table2 { get; set; }

    public virtual void Commit()
    {
        base.SaveChanges();
    }
}

Thanks,

Rich

回答1:

When doing update-database you should specify the project that contains the migrations. Make sure that you have an app.config file in that project that contains the correct connection string.

When splitting up an application over several projects, the connection string used when running the app is the one of the project started. When migrating, the connection string used is the one of the project containing the migrations.

When I did a similar setup I had to add the connection string in two places. A bit awkward, but it works.

回答2:

You can avoid managing it in app.config by offering it as a parameter:

Update-Database -Verbose 
 -ConnectionString "CONNECTIONSTRING" 
 -ConnectionProviderName "System.Data.SqlClient"
 -StartupProjectName WEBSITE_PROJECT -ProjectName MIGRATION_PROJECT

Easy-piezy, if you love to type endlessly.

回答3:

You can have your connection string stored in the web.config in your website project and the DBContext and migration files in another project and still share the same connection string. However you need to make sure that as well as setting the Data project (or whatever project has the DBContext etc. in it) as the default project for the Package Manager Console, you ALSO need to make sure that your website is set to the Default StartUp Project!!!

I cannot see this documented anywhere, but a frantic 24 hours of not being able to figure out why my migrations where suddenly being applied to a SQLExpress db, led me to this conclusion.

回答4:

I tried with Latest EF5 from Nuget.

However Update-Database does not read the App.config from the project that contain the migrations (just like the answer 1 year ago) but it will only read *.config from start up project. It is great but I discover how Add-Migration and Update-Database find a suitable connection string here:

1. It trying to get "DefaultConnection" connection string first
2. Then it is trying to get the connection string name based on context class name. E.g. I have the MyContext class derived from DbContext so I can use the "MyContext" connection string name. Useful when I have multiple db connections.
3. If both the above connection string names are not found, it will fail and show no "DefaultConnection" connection string unless you supply the -ConnectionStringName parameter. See get-help Update-Database to view the help page in the Package Manager Console.

There is no retry or fallback attempt, so if the "DefaultConnection" contains a wrong connection string, it will simply show an error.

If both DefaultConnection and context name exist in the connection strings, DefaultConnection will take precedence.

I would prefer #2 become the first try because the name is more specific but the above steps is what EF5 Migrations do when trying to connect to the db.