在运行时从子域设置EF ConnectionString以进行多租户设置

Question

Currently, my DbContext class has this code:

public ApplicationDbContext()
    : base("DefaultConnection", throwIfV1Schema: false)
{
}

public static ApplicationDbContext Create()
{
    return new ApplicationDbContext();
}

What I'd like to do, is inspect the subdomain and use that for the database name, so something like http://abc.mysite.com/ would use a connection string with database name abc .

But how do I manipulate the value of "DefaultConnection" in the constructor?

Answer 1

DBContext will take a name or a connection string in its constructor. That constructor is not usually exposed if you have a generated model.

You can use a partial class to expose that constructor:

public partial class DataEntities
{
        public DataEntities(string connectionString) : base(connectionString)
        {   
        }
}

Answer 2

I have done that before. My project was set up for DI with Castle Windsor and one of my IWindsorInstaller s was DataAccessInstaller responsible for registering, among other classes like repositories, my database context and here is the relevant code:

container.Register(Component
               .For<MyDatabaseContext>().Forward<DbContext>()
               .ImplementedBy<MyDatabaseContext>()
               .LifestylePerWebRequest()
               .UsingFactoryMethod(context =>
               {
                 return MyDatabaseContextFactory.Create(HttpContext.Current.Request.Url);
               }));

You can have several connection strings set up in your web.config matching your domain.

My context factory implementation:

public static class MyDatabaseContextFactory
{
    public static MyDatabaseContext Create(Uri uri)
    {
        return new MyDatabaseContext(uri.GetTopDomain());
    }
}

If you just have a simple project and don't even have DI, you can still make use of a factory that finds out what the website use and instantiates a database context with the appropriate connection string.

Needless to say, your current database context constructor doesn't have to change.