public static ValidationResult Validate <TConcrete>(this SimpleRulesEngine engine, TConcrete src)
     where TConcrete : class
 {
     return(engine.Validate(new List <TConcrete> {
         src
     }).First());
 }
 public static IEnumerable <ValidationResult> Validate <TConcrete>(this SimpleRulesEngine engine, List <TConcrete> src)
     where TConcrete : class
 {
     return(engine.Validate(src));
 }