Settings.OnConfiguration

Intro

This setting has no effect on EF 6. It is only used for EF Core.

Normally the connection string is passed via Startup.ConfigureServices and IMyDbContext is dependency injected into your controllers using:

services.AddDbContext<MyDbContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("MyDbContext")));

...

// Scoped is usually what you need for a database context.
// You get back the same database object within a request.
services.AddScoped<IMyDbContext, MyDbContext>();

or by manually choosing a connection string with:

var optionsBuilder = new DbContextOptionsBuilder<MyDbContext>();
optionsBuilder.UseSqlServer("Data Source=(local);Initial Catalog=Northwind;Integrated Security=True;Encrypt=false;TrustServerCertificate=true");
var db = new MyDbContext(optionsBuilder.Options);

or by passing in an IConfiguration via a constructor of the DB context:

private readonly IConfiguration _configuration;

public MyDbContext(IConfiguration configuration)
{
    _configuration = configuration;
}

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    if (!optionsBuilder.IsConfigured && _configuration != null)
    {
        optionsBuilder.UseSqlServer(_configuration.GetConnectionString("MyDbContext"));
    }
}

OnConfiguration enumeration

The OnConfiguration enumeration controls the generation of the DbContext.OnConfiguration() function in different ways:

Settings.OnConfiguration = OnConfiguration.Configuration

The code is generated as:

private readonly IConfiguration _configuration;

public MyDbContext(IConfiguration configuration)
{
    _configuration = configuration;
}

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    if (!optionsBuilder.IsConfigured && _configuration != null)
    {
        optionsBuilder.UseSqlServer(_configuration.GetConnectionString(@"MyDbContext"));
    }
}

Settings.OnConfiguration = OnConfiguration.ConnectionString

The code is generated as:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    if (!optionsBuilder.IsConfigured)
    {
        optionsBuilder.UseSqlServer(@"Data Source=(local);Initial Catalog=Northwind;Integrated Security=True;Encrypt=false;TrustServerCertificate=true");
    }
}

The above connection string is taken from your setting of Settings.ConnectionString.

Settings.OnConfiguration = OnConfiguration.Omit

This completely removes the OnConfiguring function altogether. This assumes IMyDbContext is dependency injected into your controllers/services/classes, and that you have set up your connection using:

services.AddDbContext<MyDbContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("MyDbContext")));

...

// Scoped is usually what you need for a database context.
// You get back the same database object within a request.
services.AddScoped<IMyDbContext, MyDbContext>();