Configuration locator

ASP.NET Core bring cool feature like options pattern but did you feel sometimes that is difficult to trace from which section in appsettings.json file this options come from?

To reduce need register each options class separately and better traceability, this library does that automatically.

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Getting started

Installation

Install Crip.Extensions.ConfigLocator NuGet package, or GitHub package

Prerequisites

Register all options providing assemblies where to search for classes with ConfigLocation or ConfigValidate attributes.

using Crip.Extensions.ConfigLocator;

builder.Services.AddConfigLocator(builder.Configuration, typeof(Program).Assembly);

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Usage

Decorate options with ConfigLocation attribute:

using Crip.Extensions.ConfigLocator;

[ConfigLocation("Path:To:Configuration:Section")]
public class MyOptions
{
    public string Property { get; set; }
}

Obtain options within DI container:

public class MyController
{
    public MyController(
        IOptions<MyOptions> singleton,
        IOptionsSnapshot<TOptions> snapshot,
        IOptionsMonitor<TOptions> monitor)
    {
        //...
    }
}

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Validation

Option pattern supports multiple validation options. More about Options validation.

Data annotation validation

Define options with data annotation validation:

using Crip.Extensions.ConfigLocator;
using System.ComponentModel.DataAnnotations;

[ConfigLocation("MySection")]
[ConfigValidate]
public class MyOptions
{
    [Required]
    public string Foo { get; set; } = null!;
}

When MySection:Foo is null in appsettings.json file, application will throw exception:

Microsoft.Extensions.Options.OptionsValidationException:
 DataAnnotation validation failed for 'AttributeOptions' members: 'Foo' with the error: 'The Property field is required.'.

Custom option validator

Define custom validator and register configuration with it:

public class MyOptionsValidator : IValidateOptions<MyOptions>
{
    public ValidateOptionsResult Validate(string? name, MyOptions options)
    {
        if (options.Foo == "Bar")
            return ValidateOptionsResult.Fail("Options 'Foo' value cannot be an 'Bar'");

        return ValidateOptionsResult.Success;
    }
}

[ConfigLocation("MySection")]
[ConfigValidate<MyOptionsValidator>]
// if you under C# 11 or you like to provide more than one validator:
// [ConfigValidate(typeof(MyOptionsValidator))]
public class MyOptions
{
    public string Foo { get; set; } = null!;
}

When MySection:Foo is Bar in appsettings.json file, application will throw exception:

Microsoft.Extensions.Options.OptionsValidationException:
 Options 'Foo' value cannot be an 'Bar'

Options as validatable object

As an addition your options class may implement IValidatableObject interface for some custom inline validation.

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Additional documentation

• Options pattern in ASP.NET Core

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Limitations

This package does not support named options.