AddValidatedOptions 1.0.7

AddValidatedOptions

AddValidatedOptions is a lightweight NuGet package that automatically validates strongly‑typed configuration options at startup using DataAnnotations, ensuring fail‑fast behavior for ASP.NET Core applications

Installation

Install the package from NuGet:

dotnet add package AddValidatedOptions

Usage

If configuration is invalid, clear error messages are logged and the app fails fast.

What kind of errors can occur?

Validation uses DataAnnotations ([Required], [Range], [EmailAddress], etc.) applied to your configuration class.
If the values in appsettings.json do not match these rules, the application will stop at startup and print clear error messages.

Example

public class MyAppSettings
{
    [Required]
    public string ApiKey { get; set; }

    [Range(1, 10)]
    public int RetryCount { get; set; }

    [EmailAddress]
    public string SupportEmail { get; set; }
}

---------------------------------------------

Program.cs:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddValidatedOptions<MyAppSettings>(builder.Configuration,"MyAppSettings");

//...

var app = builder.Build();

app.MapGet("/", ([FromServices] MyAppSettings settings) =>
{
    return $"ApiKey: {settings.ApiKey}, RetryCount: {settings.RetryCount}";
});

app.Run();

---------------------------------------------

Valid appsettings.json:

{
  "MyAppSettings": {
    "ApiKey": "12345-ABCDE",
    "RetryCount": 5,
    "SupportEmail": "help@company.com"
  }
}

---------------------------------------------

Invalid appsettings.json:
{
  "MyAppSettings": {
    "RetryCount": 0,
    "SupportEmail": "not-an-email"
  }
}

### Resulting errors

[Configuration Error] Section 'MyAppSettings': The ApiKey field is required.
[Configuration Error] Section 'MyAppSettings': The field RetryCount must be between 1 and 10.
[Configuration Error] Section 'MyAppSettings': The SupportEmail field is not a valid e-mail address.

Benefits

• Fail fast: detect missing or invalid configuration before the app runs.
• Clear logs: errors are printed in console with section name and message.
• Strong typing: leverage IOptions<T> with validation rules.

⚖️ License

This project is freely available under the MIT license.
You may use it without restrictions, as long as you retain the reference to the original license.