protected override ValidationResult IsValid(object value, ValidationContext validationContext) { string cpf = (value as string).Trim(); IBusinessRepository _context = (IBusinessRepository)validationContext.GetService(typeof(IBusinessRepository)); Models.Business obj = (Models.Business)validationContext.ObjectInstance; List <Models.Business> list = (List <Models.Business>)_context.FindAllsCpf(cpf); if (list.Count > 1) { return(new ValidationResult("Cpf já cadastrado")); } if (list.Count == 1 && obj.Id != list[0].Id) { return(new ValidationResult("Cpf já cadastrado")); } return(ValidationResult.Success); }