protected virtual ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            string Email = value as string;

            ICollaboratorRepository _cRepo       = (ICollaboratorRepository)validationContext.GetService(typeof(ICollaboratorRepository));
            List <Collaborator>     collaborator = (List <Collaborator>)_cRepo.GetByEmail(Email);

            Collaborator objCollaborator = (Collaborator)validationContext.ObjectInstance;

            if (collaborator.Count > 1)
            {
                return(new ValidationResult("Este E-mail já está cadastrado"));
            }
            else if (collaborator.Count == 1 && objCollaborator.Id != collaborator[0].Id)
            {
                return(new ValidationResult("Este E-mail já está cadastrado"));
            }
            return(base.IsValid(value, validationContext));
        }