Where to place fluentvalidation validator class in a two project solution

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C#

MVC

validation

I have a web project and a class library project in one solution. The class library project contains the models for all non-identity data. I have created a validator class to validate uniqueness in a table (Category). When I place the Unique attribute into the model, I get "The Type or namespace name 'CategoryValidator' could not be found...'.

Here is CategoryValidator class

namespace Spicy.Entities.Validators
{
    public class CategoryValidator : AbstractValidator<Category>
    {
        public CategoryValidator()
        {
            RuleFor(x => x.Name).NotNull().WithMessage("Category Name is required.").Must(UniqueName).WithMessage("This category name already exists.");
        }

        private bool UniqueName(Category category, string name)
        {
            using (RecipeContext db = new RecipeContext())
            {
                var dbCategory = db.Categories
                                .Where(x => x.Name.ToLower() == name.ToLower())
                                .SingleOrDefault();

                if (dbCategory == null)
                    return true;

                return dbCategory.ID == category.ID;
            }
        }
    }
}

Here is the Category Model

using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Spicy.Entities
{
    [Validator(typeof(CategoryValidator))]
    public class Category
    {
        public int ID { get; set; }

        [StringLength(20, ErrorMessage = "Category cannot be longer than 20 characters")]
        [Required]

        public string Name { get; set; }

        [Required]
        [DisplayName("User Name")]
        [StringLength(20, ErrorMessage = "User Name cannot be longer than 20 characters")]
        public string UserName { get; set; }

        public virtual ICollection<Recipe> Recipes { get; set; }
    }

Here is the global.asax code

public class MvcApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

        FluentValidationModelValidatorProvider.Configure();
    }
}

Where should I put the validator class and how do I get around the issues I'm having?

help.

What I have tried:

When I place the validator class into the class library project, it cannot access the context (RecipeContext) from the web project. If I try placing the validator class into the web app, I get an error that 'The Type or namespace name ' CategoryValidator' could not be found...'. I have also tried installing Fluent Validation package in both projects.