Multiple DbContext, multiple Database.SetInitializer

Question

I have created two DbContexts, one is for application configuration, the second is for logging.

The reason being, I want to set a maximum size on the logging db so it doesn't use up all free disk space and prevent other databases from working.

In my global.asax.cs file, I have the following:

        protected void Application_Start()
    {

        AreaRegistration.RegisterAllAreas();

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);

        Database.SetInitializer<AdminContext>(new AdminInitialiser());
        Database.SetInitializer<LoggingContext>(new LoggingInitialiser());
    }

The InitializeDatabase method in LoggingInitialiser is not being called. Is this because only one initializer can be set? Is there any way to have initializers for two DbContexts?

danludwig · Accepted Answer · 2012-06-25 15:00:36Z

9

Set the initializer in the DbContext constructor instead.

public class AdminContext : DbContext
{
    public AdminContext()
    {
        Database.SetInitializer(new AdminInitialiser());
    }
}

public class LoggingContext : DbContext
{
    public LoggingContext()
    {
        Database.SetInitializer(new LoggingInitialiser());
    }
}

edited Jun 25, 2012 at 15:00

answered Jun 25, 2012 at 14:21

danludwig

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1 Comment

Holf Over a year ago

Isn't there a risk that this is going to get called multiple times? I suspect initialisation is expensive, even if there are no changes to deploy. How about if you put it in a static constructor, meaning it will only ever get called once?

Sylvia · Accepted Answer · 2012-06-29 10:04:13Z

4

Yes you can do it. You just need to initialize before you move on to the next one.

  Database.SetInitializer<MyDBContext>(myInitializer);
  MyDbContext context = new MyDbContext();
  context.Database.Initialize(false);

  Database.SetInitializer<MySecondDBContext>(myInitializer);
  MySecondDbContext context2 = new MySecondDbContext();
  context2.Database.Initialize(false);

Note: that I usually get the DbContext instance from a dependency resolver...

answered Jun 29, 2012 at 10:04

Sylvia

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Comments

Yang Zhang · Accepted Answer · 2015-07-16 00:20:05Z

3

I suggest to put the SetInitializer call to static constructor like below:

    static ApplicationIdentityDbContext()
    {
        Database.SetInitializer(new IdentityDbInitializer());
    }

Below is from MSDN

A static constructor is used to initialize any static data, or to perform a particular action that needs to be performed once only. It is called automatically before the first instance is created or any static members are referenced.

So static constructor is ideal for initialize database. I have used this technique for multiple database and it works well for me.

answered Jul 16, 2015 at 0:20

Yang Zhang

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