Question

The latest EF Code First NuGet package comes with a custom implementation of IDatabaseInitializer called DontDropDbJustCreateTablesIfModelChanged. As the name implies, when a model change is detected, it will not drop and recreate the whole database, just drop and recreate the tables.

Say I have this model class:

public class User
{
    public string Username { get; set; }

    // This property is new; the model has changed!
    public string OpenID { get; set; }
}

How would one go about implementing an IDatabaseInitializer that doesn’t drop any tables either. In this case, it would just add an OpenID column to the User table?

Answer 1

I think it is a matter of SQL. So for SQL Server you can write something like:

public class MyInitializer : IDatabaseInitializer<MyContext>
{
    public void InitializeDatabase(MyContext context)
    {
        context.Database.SqlCommand(
            @"
            IF NOT EXISTS (SELECT 1 FROM sys.columns AS col
                           INNER JOIN sys.tables AS tab ON tab.object_Id = col.object_Id
                           WHERE tab.Name = 'User' AND col.Name = 'OpenId')
            BEGIN
                ALTER TABLE dbo.User ADD OpenId INT; 
            END");
    }
}

But in the same way you can execute such script without adding it to your application which I think is much better approach.