Wire up IServiceProvider when validating DataAnnotations attributes on Options

[akilin]

Describe the bug

App was unable to resolve IWebHostEnvironment from ValidationContext when validating options with custom Required attribute inside Configure method.

To Reproduce

IWebHostEnvironment not resolving, when trying to create a custom validation attribute to make something required only in Production environment.

Relevant code snippets

    public class DemoOptions
    {
        [RequiredInProd]
        public string FooBar { get; set; }
    }

    public class RequiredInProd : RequiredAttribute
    {
        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            //this errors
            var env = validationContext.GetRequiredService<IWebHostEnvironment>();
            return ValidationResult.Success;
        }
    }
//Startup.cs methods
public void ConfigureServices(IServiceCollection services)
        {
            services.AddOptions<DemoOptions>()
                .Bind(Configuration.GetSection(nameof(DemoOptions)))
                .ValidateDataAnnotations();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //this line works fine and IWebHostEnvironment is resolved.
            var envFromServices = app.ApplicationServices.GetRequiredService<IWebHostEnvironment>();
            //this errors when trying to resolve IWebHostEnvironment inside Attribute methods
            _ = app.ApplicationServices.GetRequiredService<IOptions<DemoOptions>>().Value;
        }

-->

[pranavkm]

This looks like a feature request. Options validation does not wire up the application's service provider which explains why this doesn't work.

[bordecal]

+1 for wiring up the service provider in DataAnnotationValidateOptions