C#•5mo ago

How to check options for null?

I have this:

var options = Configuration.GetSection(nameof(Patterns));
services.Configure<Patterns>(options);

var options = Configuration.GetSection(nameof(Patterns));
services.Configure<Patterns>(options);

in controller:

public ZeebeController(
  KafkaSettings kafkaSettings,
  IZeebeClient zeebeClient,
  IOptions<Patterns> options)
{ 
}

public ZeebeController(
  KafkaSettings kafkaSettings,
  IZeebeClient zeebeClient,
  IOptions<Patterns> options)
{ 
}

all I want is check options from startup for null but I can't just write if(options == null)

11 Replies

Thinker•5mo ago

According to the docs for GetSection, it returns "The specified ConfigurationSection object, or null if the section does not exist.", however the return type is object and not object?. You can probably just ignore the warning because the return type is annotated incorrectly.

TOKYODRIFT!•5mo ago

hmmm okay, I'll ignore, thanks

Joschi•5mo ago

You could also bind the configuration to a class at startup and inject that class. That also allows you to do validation.

Sir Rufo•5mo ago

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options?view=aspnetcore-7.0#options-validation

Options pattern in ASP.NET Core

Discover how to use the options pattern to represent groups of related settings in ASP.NET Core apps.

Unknown User•5mo ago

Message Not Public

MODiX•5mo ago

appsettings.json:

{
  "My": {
    "Foo": {
      "Kix": 5
    }
  }
}

{
  "My": {
    "Foo": {
      "Kix": 5
    }
  }
}

src/Foo/FooOptions.cs:

public class FooOptions
{
  public const string SectionName = "My:Foo";

  public string Bar {get;set;} = "default value for bar";
  public int Kix {get;set;} = -1;
  public DateTime? Pouet {get;set;} = default;
}

public class FooOptions
{
  public const string SectionName = "My:Foo";

  public string Bar {get;set;} = "default value for bar";
  public int Kix {get;set;} = -1;
  public DateTime? Pouet {get;set;} = default;
}

src/Foo/FooServiceCollectionExtensions.cs:

namespace Microsoft.Extensions.DependencyInjection; // <==== recommanded for service.Add so that you don't clutter Startup file

public class FooServiceCollectionExtensions
{
  public static IServiceCollection AddFoo(this IServiceCollection services) =>
    services
      .AddOptions<FooOptions>()
      .BindConfiguration(FooOptions.SectionName)
      .Validate(options => options.Kix >= 0, $"The configuration key '{FooOptions.SectionName}:{nameof(Kix)}' cannot be negative")
      ;

  public static IServiceCollection AddFoo(this IServiceCollection services, Action<FooOptions> configure) =>
    services
      .AddFoo()
      .Configure(configure);

namespace Microsoft.Extensions.DependencyInjection; // <==== recommanded for service.Add so that you don't clutter Startup file

public class FooServiceCollectionExtensions
{
  public static IServiceCollection AddFoo(this IServiceCollection services) =>
    services
      .AddOptions<FooOptions>()
      .BindConfiguration(FooOptions.SectionName)
      .Validate(options => options.Kix >= 0, $"The configuration key '{FooOptions.SectionName}:{nameof(Kix)}' cannot be negative")
      ;

  public static IServiceCollection AddFoo(this IServiceCollection services, Action<FooOptions> configure) =>
    services
      .AddFoo()
      .Configure(configure);

Program.cs / Startup.cs:

services.AddFoo();
// or
services.AddFoo(fooOptions => fooOptions.Kix = 12);

services.AddFoo();
// or
services.AddFoo(fooOptions => fooOptions.Kix = 12);

Bar.cs:

public class Bar
{
  private readonly FooOptions _fooOptions;

  // .Value in ctor is fine only if it's always ever a non-changing value (no reload and/or no scoped resolution)
  public Bar(IOptions<FooOptions> fooOptions)
    => _fooOptions = fooOptions.Value;
}

public class Bar
{
  private readonly FooOptions _fooOptions;

  // .Value in ctor is fine only if it's always ever a non-changing value (no reload and/or no scoped resolution)
  public Bar(IOptions<FooOptions> fooOptions)
    => _fooOptions = fooOptions.Value;
}

Unknown User•5mo ago

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Joschi•5mo ago

Didn't .NET 8 also add a Source Gen for Options Validations?

Unknown User•5mo ago

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TOKYODRIFT!•5mo ago

is it possible to test that "My" section is exist?

Unknown User•5mo ago

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How to check options for null?