RequiresACorrespondingConcreteImplementationConvention.cs

using Conventional;
using Conventional.Conventions;
using System;
using System.Linq;

namespace Conventions
{
    public static class Convention
    {
        public static RequiresACorrespondingConcreteImplementationConventionSpecification InterfaceMustHaveCorrespondingConcreteType(Type[] subjects)
        {
            return new RequiresACorrespondingConcreteImplementationConventionSpecification(subjects);
        } 
    }
    
    public class RequiresACorrespondingConcreteImplementationConventionSpecification : ConventionSpecification
    {
        private readonly Type[] _subjects;

        public RequiresACorrespondingConcreteImplementationConventionSpecification(Type[] subjects)
        {
            _subjects = subjects;
        }

        protected override string FailureMessage
        {
            get { return "Could not find required corresponding implementation of {0}"; }
        }

        public override ConventionResult IsSatisfiedBy(Type type)
        {
            if (_subjects.SelectMany(x => x.GetInterfaces()).Any(i => i == type))
            {
                return ConventionResult.Satisfied(type.FullName);
            }

            return ConventionResult.NotSatisfied(type.FullName, string.Format(FailureMessage, type.FullName));
        }
    }
}