public DropdownFieldBuilder(FieldBuilder <TProperty, TEntity> parent, DataField field)
 {
     _field  = field;
     _parent = parent;
 }
        private void CustomRule(IDataForm form, IEnumerable <DataField> fields, object item, int rowIndex, DataField field, List <ValidationResult> result,
                                FormRuleTriggers trigger)
        {
            var rules = field.Rules.Where(r => r.Trigger == trigger ||
                                          (trigger == FormRuleTriggers.ChangeSubmit && (r.Trigger == FormRuleTriggers.Change || r.Trigger == FormRuleTriggers.Submit)) ||
                                          (trigger == FormRuleTriggers.Submit && (r.Trigger == FormRuleTriggers.Change || r.Trigger == FormRuleTriggers.Submit || r.Trigger == FormRuleTriggers.ChangeSubmit)) ||
                                          (trigger == FormRuleTriggers.Change && (r.Trigger == FormRuleTriggers.Change || r.Trigger == FormRuleTriggers.Submit || r.Trigger == FormRuleTriggers.ChangeSubmit))
                                          );

            foreach (var rule in rules)
            {
                FormRuleResult vr;

                if (rule.Method != null)
                {
                    vr = rule.Method(item);
                }
                else
                {
                    Type argsType = typeof(RuleArgs <>).MakeGenericType(rule.EntityType);
                    var  args     = Activator.CreateInstance(argsType, item) as RuleArgs;
                    vr = rule.MethodArgs(args);
                    var ruleFields = args.EntityBuilder.GetFieldDictionary();

                    //ToDo: update fields appearance here
                    foreach (var f in fields)
                    {
                        var rf = ruleFields[f.BindingProperty];
                        f.Required = rf.Required;
                        f.Hidden   = rf.Hidden;
                        f.ReadOnly = rf.ReadOnly;
                        f.Label    = rf.Label;
                    }
                }

                if (vr != null && vr.IsFailed)
                {
                    result.Add(new ValidationResult
                    {
                        Message              = $"{vr.RuleName}: {vr.Message}",
                        BindingProperty      = field.BindingProperty,
                        ValidationResultType = ValidationResultTypes.Error,
                        RowIndex             = rowIndex
                    });
                }
            }
        }