When creating a custom ValidationAttribute, the ValidationContext always don't have a valid ServiceContainer

[jlVidal]

Following this article: https://andrewlock.net/injecting-services-into-validationattributes-in-asp-net-core/

When creating custom ValidationAttribute several people already note that is impossible to access/get any service from the GetService method inside the ValidationContext class, ServiceContainer property. Looking into the code is possible to see:

            var context = new ValidationContext(
                instance: container ?? validationContext.Model,
                serviceProvider: validationContext.ActionContext?.HttpContext?.RequestServices,
                items: null)
            {
                DisplayName = metadata.GetDisplayName(),
                MemberName = memberName
            };

https://github.com/aspnet/Mvc/blob/760c8f38678118734399c58c2dac981ea6e47046/src/Microsoft.AspNetCore.Mvc.DataAnnotations/Internal/DataAnnotationsModelValidator.cs

Since the ActionContext was obsolete: https://stackoverflow.com/questions/37286530/actioncontext-gone-in-microsoft-aspnetcore-mvc-controller - The service provider for a validation attribute is always null or empty. Let's make the ValidationAttribute great again, please fix this issue in the next patch.

[rynowak]

Are you saying that 328f4d6 does not fix this issue?

It's certainly our intent that ValidationContext has the right service provider.

[jlVidal]

To be confirmed... Since I'm compiling against NET452 I can't test in the newer/beta version (2.0.0-preview1) If fixed, I believe that should be explicit mentioned in the release notes.

@rynowak thanks for the follow up anyway

[rynowak]

@jlVidal - 328f4d6 dates all the way back to 1.0.0-rc2 so I expect this to be working in whatever release you are using.

Can you please clarify for me... is this working for you or not?

[jlVidal]

It's working in new/blank project! I'm still trying to figure out why my specific solution doesn't work correctly.. I can't request any services to the ServiceProvider (always returns null). I'm using:

    <PackageReference Include="Microsoft.AspNetCore" Version="1.1.2" />
    <PackageReference Include="Microsoft.AspNetCore.Authentication.Cookies" Version="1.1.2" />
    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="1.1.2" />
    <PackageReference Include="Microsoft.AspNetCore.DataProtection.Extensions" Version="1.1.2" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="1.1.3" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc.WebApiCompatShim" Version="1.1.3" />
    <PackageReference Include="Microsoft.AspNetCore.ResponseCompression" Version="1.0.2" />
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="1.1.2" />
    <PackageReference Include="Swashbuckle.AspNetCore" Version="1.0.0" />

EDIT: OK I found the issue:

I was trying to do:

            var result = validationContext.ServiceContainer.GetService(typeof(FooServiceTest));
            if (result == null)
                throw new ArgumentNullException(nameof(result));

but the way that works is:

            var result = validationContext.GetService(typeof(FooServiceTest));
            if (result == null)
                throw new ArgumentNullException(nameof(result));

API call problem 😢 - so the bug exists with the ServiceContainer property.

[rynowak]

https://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.validationcontext.servicecontainer(v=vs.110).aspx#Anchor_1

Yeah that's a bit of a bizzare property. I guess it's intended for you to be able to share state? Since service provider is read-only but service container is r/w.

Ok, going to close this since there's no actual ASP.NET problem. Glad you got it figured out.