Entity Framework in Visual Studio: database is not created with DbContext base constructor

Question

I'm brand new to Visual Studio and .NET, and I'm following this tutorial on Lynda (Code-first development with the Entity Framework) to create an ASP.NET MVC app where I should be able to add Tour objects to a database using a form.

I've created a class MyDbContext that inherits from DbContext.

I've added a base class constructor with the name of the database that needs to be created for this app when information is submitted from the form. I've also added a DbSet named Tours that holds the tour objects.

Here is that code, in MyDBContext.cs:

public class MyDBContext : DbContext
{
    public MyDBContext() : base("ExploreCalifornia")
    {

    }

    public DbSet<Tour> Tours { get; set; }
}

In the Tour Controller, I create an instance of MyDbContext named db:

private MyDBContext db = new MyDBContext();

I have a Create page that contains the form to add a new tour, and here is the POST route for this page:

[HttpPost]
public ActionResult Create(Tour tour)
{
    try
    {
        db.Tours.Add(tour);
        db.SaveChanges();

        return RedirectToAction("Index");
    }
    catch
    {
        return View();
    }
}

Following with the debugger, when I try to add a new tour, it skips over the SaveChanges line and goes directly into the catch block. No database is ever created, and nothing shows up under App_Data in the Solution Explorer.

The tutorial mentions that the database will be created using SQL Server Express LocalDB, but I don't see any reference to LocalDB in the Server Explorer. This is still new, so I'm a little lost on how to approach this.

Any ideas of what might be going wrong, or where to start looking?

change the line catch { to catch (Exception ex) { and set a breakpoint on return View(); - you should then have some detail about the actual problem - at the moment you have no way of knowing what's going on at all. — Robert Foster
– Robert Foster, Commented Oct 21, 2015 at 0:31

Vladimir Svyatski · Accepted Answer · 2015-10-21 01:40:15Z

Thing is, when you use DbContext's contructor with a string parameter, the parameter must be either 1. name of a connection string from your app.config or web.config in the form name=MyConnectionString. For instance, your config contains

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="MyConnectionString" connectionString="your str here" />
  </connectionStrings>
</configuration>

and you declare your context like this

public class MyDBContext : DbContext
{
    public MyDBContext() : base("name=MyConnectionString")
    {

    }

    public DbSet<Tour> Tours { get; set; }
}

or 2. direct connection string, like this

public class MyDBContext : DbContext
{
    public MyDBContext() : base("Server=(local), Database=MyDBName, User=blah-blah...")
    {

    }

    public DbSet<Tour> Tours { get; set; }
}

Please, take note that if you use a config file, it must be in your AppDomain directory (for exe it's its folder; for a web site it's the site's bin folder).

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