Unable to resolve service for type for generic class

Question

I am using FluentValidation and I have created a generic class like so:

public class GenericValidator<T>: AbstractValidator<T>
{
    protected override bool PreValidate(ValidationContext<T> context, ValidationResult result)
    {
        if (context.InstanceToValidate != null) return true;

        result.Errors.Add(new ValidationFailure("model", Resources.NullModelError));

        return false;
    }
}

When I tried to use my application, it returned this error:

System.InvalidOperationException: Unable to resolve service for type 'Api.Controllers.Strategies.StrategyValidator' while attempting to activate 'Api.Controllers.Strategies.Handlers.StrategySaveHandler'.

My StrategyValidator looks like this:

public class StrategyValidator : GenericValidator<StrategyViewModel>
{
    public StrategyValidator()
    {
        RuleFor(model => model.Url).NotEmpty();
    }
}

I have a few of these for different entities and I would like to register them all. I have tried a few ways:

services.AddSingleton(typeof(GenericValidator<>));

services.AddSingleton(typeof(GenericValidator<>), typeof(GenericValidator<>));

services.AddSingleton(typeof(AbstractValidator<>));

services.AddSingleton(typeof(GenericValidator<>), typeof(AbstractValidator<>));

None of them worked. Does anyone know what I can do to register all my validators rather than registering them one by one?

Answer 1

You haven't provided what the service requiring the DI looks like but you could register your validators manually like so: services.AddSingleton(typeof(StrategyValidator))

Additionally you may just want to leverage the generic forms in your services eg instead of requesting a StrategyValidator you should request a GenericValidator<StrategyViewModel>

But generally, Fluent provides an easy way of doing this using their extension methods

eg

services.AddMvc(config =>
{
    config.Filters.Add(new AuthorizeFilter(authorizationPolicy));
}).AddFluentValidation(fv => fv.RegisterValidatorsFromAssemblyContaining<Startup>())

Note: this will register all of the fluent validators that are within the same assembly as Startup.