adding-validation-to-strongly-typed-configuration-objects-in-dotnet-6/

[giscus[bot]]

adding-validation-to-strongly-typed-configuration-objects-in-dotnet-6/

In this post I describe how to to verify your strongly typed configuration objects are correctly bound to your configuration at app startup

https://andrewlock.net/adding-validation-to-strongly-typed-configuration-objects-in-dotnet-6/

[Van-Dame]

This would work fine in cases where DataAnnotations were being used. Do you have any idea how do the same (preferably with equal simplicity) in case of FluentValidations?

[andrewlock]

https://andrewlock.net/adding-validation-to-strongly-typed-configuration-objects-using-flentvalidation/ 🙂

[Van-Dame]

Yeah, you published this one 2 days after (iirc) 🙂 Thanks for the extremely useful post!

[petrkoutnycz]

I guess you can do it via OptionsBuilder.Validate() method with your own predicate.

[RehanSaeed]

I've been doing something very similar for a long time. I use these extension methods below to simplify this boilerplate which may help someone:

https://github.com/Dotnet-Boxed/Framework/blob/add335b5729b784029069ab23432dcfe06893695/Source/Boxed.AspNetCore/ServiceCollectionExtensions.cs#L129-L299

[lv1il0s]

Thanks for a great article, as always. I would just warn readers that this approach doesn't support nested appsettings structure - dotnet/runtime#36093

[chrisxfire]

In a .NET 6 console app, how would this work under the IHostBuilder.ConfigureServices method since ValidateOnStart returns an OptionsBuilder<T>?

public class Program
{
    private static async Task Main(string[] args)
    {
        IHostBuilder hostBuilder = new HostBuilder()
            .ConfigureAppConfiguration((context, configuration) =>
            {
                _ = configuration
                    .AddJsonFile("./config/appsettings.json", optional: false, reloadOnChange: false)
                    .Build();
            })
            .ConfigureServices((context, services) =>
            {
                _ = services
                    // I could call .Configure here, but not .AddOptions or .ValidateOnStart
                    .AddHostedService<AppService>()
                ...
            .UseContentRoot(Environment.CurrentDirectory)
            .UseSerilog((context, services, loggerConfiguration) =>
            ...

[andrewlock]

You call it in exactly the same way 🤔 you don't have to chain everything into a single fluent call. There's no reason to chain anything tbh, beyond aesthetics...

 public class Program
{
    private static async Task Main(string[] args)
    {
        IHostBuilder hostBuilder = new HostBuilder()
            .ConfigureAppConfiguration((context, configuration) =>
            {
                   configuration.AddJsonFile("./config/appsettings.json", optional: false, reloadOnChange: false);
                     // .Build(); // don't call this
            })
            .ConfigureServices((context, services) =>
            {
                services.AddOptions<T>();
                services.Configure<T2>();
                services.AddHostedService<AppS>()
             });

[chrisxfire]

Well, this is... embarrassing.

Thanks.

[savcic-milorad]

Hi Andrew, this looks great.

However I cannot resolve ValidateDataAnnotations(), I have installed the nuget package Microsoft.Extensions.DependencyInjection (7.0.0)

I have the ValidateOnStart() method which is confusing

[andrewlock]

I have installed the nuget package Microsoft.Extensions.DependencyInjection

You shouldn't need to install this if you're using aspnetcore 🤔

As you can see in the repo, no extra packages are needed, just a couple of namespaces, as long as you're using <Project Sdk="Microsoft.NET.Sdk.Web"> in your .csproj file.

If you're using a different SDK, you'll need this package instead (note the missing .Options): https://www.nuget.org/packages/Microsoft.Extensions.Options.DataAnnotations

[savcic-milorad]

This did resolve it, thank you Andrew.
My code is in a class library project so I am using a different SDK (Microsoft.NET.Sdk). Adding this NuGet package added the required extension method.

[ci-vamp]

thank you for this great post andrew. i could not figure out how to get it to work until i saw the [Required] annotations being used!

one thing i am noticing is that it will only validate top-level properties. i created an AppSettings class with sub-settings built into it. it is not validating any of the sub-settings class properties.

so it looks something like this

public class AppSettings
{
  [Required]
  public string TopLevel { get; init; }

  [Required]
  public NestedSettings { get; init; }

  ...
}

public class NestedSettings
{
  [Required]
  public string Nested { get; init; }

  ...
}

the nested settings are binded properly and accessible through injecting AppSettings (direct or through IOptions) but are just not validated.

so two questions:

1. is it an anti-pattern to have these nested settings?
2. is it possible to perform the validation on the nested settings?

[ci-vamp]

typo in the example but i cannot edit - it should be public NestedSettings NestedSettings { get; init; } of course

[petrkoutnycz]

IMO it is not an anti-pattern, I use it in our projects too. Though you are true, it does not work at the moment. See this issue: dotnet/runtime#36093.

The only workaround I see is to implement IValidatableObject to validate also nested objects.

[kalpeshparakh]

This post so wonderfully explains the pattern. The validation part is just so goood...