Settings.OnConfiguration

Settings.OnConfiguration

Applies to EF Core only. Has no effect on EF 6.

Controls what code is generated inside DbContext.OnConfiguring().

public enum OnConfiguration
{
    Configuration,    // IConfiguration injected via constructor; reads connection string from appsettings.json
    ConnectionString, // Connection string embedded directly in OnConfiguring
    Omit              // OnConfiguring method removed entirely
}

Set in Database.tt:

Settings.OnConfiguration = OnConfiguration.ConnectionString;

---

OnConfiguration.Configuration

Injects IConfiguration via the constructor and reads the connection string from appsettings.json.

Generated code:

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"));
}

Required in appsettings.json:

{
  "ConnectionStrings": {
    "MyDbContext": "Data Source=(local);Initial Catalog=MyDatabase;Integrated Security=True"
  }
}

The key "MyDbContext" is controlled by Settings.ConnectionStringName.

---

OnConfiguration.ConnectionString

Embeds the connection string directly in OnConfiguring. The value comes from Settings.ConnectionString.

Generated code:

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

Security note: This embeds the connection string in compiled code. Do not use in production with sensitive credentials. Consider OnConfiguration.Configuration or OnConfiguration.Omit for production applications.

---

OnConfiguration.Omit

Removes OnConfiguring entirely. The application is responsible for providing the DbContextOptions — typically via dependency injection.

Generated code: No OnConfiguring method.

Register in Startup.cs / Program.cs:

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

builder.Services.AddScoped<IMyDbContext, MyDbContext>();

This is the recommended approach for ASP.NET Core applications.

---

ConnectionStringActions

Use Settings.ConnectionStringActions to append extra method calls to the connection setup. Works with all three OnConfiguration modes.

Settings.ConnectionStringActions = ".EnableRetryOnFailure(maxRetryCount: 10, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null)";

Generated result:

optionsBuilder.UseSqlServer(@"...", x => x
    .EnableRetryOnFailure(maxRetryCount: 10, maxRetryDelay: TimeSpan.FromSeconds(30), errorNumbersToAdd: null));

Download example

Here is a small EFCore console application using Settings.OnConfiguration = OnConfiguration.Configuration; and loading its connection string from appsettings.{environment}.json during runtime.