Philiprehberger.ConfigValidator

Validate appsettings.json configuration sections at startup with attribute-based rules.

Installation

dotnet add package Philiprehberger.ConfigValidator

Usage

Define your options class with validation attributes

using Philiprehberger.ConfigValidator;

public class SmtpOptions
{
    [Required]
    public string Host { get; set; } = "";

    [Range(1, 65535)]
    public int Port { get; set; }

    [Required]
    [Pattern(@"^[^@]+@[^@]+\.[^@]+$")]
    public string FromAddress { get; set; } = "";

    [MinLength(1)]
    [MaxLength(100)]
    public string Username { get; set; } = "";
}

Register and validate at startup (fail-fast)

using Philiprehberger.ConfigValidator;

var builder = WebApplication.CreateBuilder(args);

builder.Services.ValidateConfiguration<SmtpOptions>(
    builder.Configuration,
    "Smtp");

var app = builder.Build();
app.Run();

If any validation rule fails, a ConfigValidationException is thrown immediately at startup with all errors listed.

Check without throwing

var errors = ConfigValidator.Check<SmtpOptions>(configuration, "Smtp");

foreach (var error in errors)
{
    Console.WriteLine(error);
}

API

Attributes

Attribute	Target	Description
[Required]	Property	Value must be present and non-null/non-empty
[Pattern(regex)]	String property	Value must match the regular expression
[Range(min, max)]	Numeric property	Value must be within range (inclusive)
[MinLength(n)]	String/collection	Length/count must be at least n
[MaxLength(n)]	String/collection	Length/count must be at most n

ConfigValidator

Method	Description
Validate<T>(IConfiguration, string)	Binds section to T, validates, throws ConfigValidationException on failure
Check<T>(IConfiguration, string)	Binds section to T, validates, returns list of error strings

ConfigValidatorExtensions

Method	Description
ValidateConfiguration<T>(IServiceCollection, IConfiguration, string)	Validates at registration time and registers the bound instance as a singleton

ConfigValidationException

Member	Description
Errors	IReadOnlyList<string> of all validation error messages
Message	Formatted string listing all errors

Development

dotnet build src/Philiprehberger.ConfigValidator.csproj --configuration Release

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License

MIT