C#•3mo ago

Is there a method that throws an exception if a config value is not present in appsettings?

Hello, Getting configuration values from appsettings.json is done via calling builder.Configuration["name"]. This way few of my services might get a null property, without throwing error before build. Is there an existing method that will throw an exception if the config value is null?

9 Replies

Kringe•3mo ago

you could make a simple extension method for this

    public static string GetRequiredValue(this IConfiguration configuration, string key) => 
        configuration[key] ?? throw new InvalidOperationException($"Configuration value for '{key}' is null");

var value = configuration.GetRequiredValue("key");

    public static string GetRequiredValue(this IConfiguration configuration, string key) => 
        configuration[key] ?? throw new InvalidOperationException($"Configuration value for '{key}' is null");

var value = configuration.GetRequiredValue("key");

Angius•3mo ago

https://learn.microsoft.com/en-us/dotnet/core/extensions/options-validation-generator

Compile-time options validation source generation - .NET

Learn how to utilize compile-time source generation for validating options.

Kringe•3mo ago

ty I will read

CoreOP•3mo ago

Thank you This is just what I needed

Unknown User•3mo ago

Message Not Public

MODiX•3mo 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•3mo ago

Message Not Public

CoreOP•3mo ago

Than you

Kringe•3mo ago

Gaming

Programming

Is there a method that throws an exception if a config value is not present in appsettings?