s Note in VB.NET

Drawer PDF-417 2d barcode in VB.NET s Note

The default IsValid and IsDirty properties must be enhanced for all objects that subclass BusinessBase and contain child objects.

A parent object is valid only if it is in a valid state and if all of its child objects are in a valid state. Likewise, a parent object is dirty if its own data has been changed or if any of its child objects or collections have been changed. To handle this properly, the IsValid and IsDirty methods must be overridden to provide a slightly more sophisticated implementation of each: Public Overrides ReadOnly Property IsValid() As Boolean Get Return MyBase.IsValid AndAlso mResources.IsValid End Get End Property Public Overrides ReadOnly Property IsDirty() As Boolean Get Return MyBase.IsDirty OrElse mResources.IsDirty End Get End Property In the case of IsValid, the Project object is checked to see if it is invalid. If it is, then the result is False and there s no need to check the child collection. Otherwise, the child collection s IsValid property is checked, which triggers a check of all the child objects it contains. If any child object is invalid, then the result is False. IsDirty is similar. In this case, the Project object is checked, and if it has been changed, then the result is True. But if the Project itself hasn t been changed, then the child collection object s IsDirty property is checked, triggering a check of all child objects it contains. If any child object has been changed, then the result is True.

The Validation Rules region implements the AddBusinessRules() method to associate validation rules to properties of the business object. As discussed in 3, validation rules are implemented as rule methods that conform to the Csla.Validation.RuleHandler delegate. This region also implements any custom rule methods for the object. The rule methods provided in Csla.Validation.CommonRules are designed to handle most common validation requirements, but some objects have rules that aren t implemented in the CommonRules class.

Let s look first at the AddBusinessRules() implementation: Protected Overrides Sub AddBusinessRules() ValidationRules.AddRule( _ AddressOf Validation.CommonRules.StringRequired, "Name") ValidationRules.AddRule( _ AddressOf Validation.CommonRules.StringMaxLength, _ New Validation.CommonRules.MaxLengthRuleArgs("Name", 50)) ValidationRules.AddRule(AddressOf StartDateGTEndDate, "Started") ValidationRules.AddRule(AddressOf StartDateGTEndDate, "Ended") End Sub This method is automatically invoked by the CSLA .NET framework any time validation rules need to be associated with the object s properties. The method should only contain a series of ValidationRules.AddRule() method calls as shown here. Each call to AddRule() associates a validation rule with a property. In the simple case, this means associating a rule method like StringRequired to a property like Name: ValidationRules.AddRule( _ AddressOf Validation.CommonRules.StringRequired, "Name") With this done, any time PropertyHasChanged() is called by the Name property, or ValidationRules.CheckRules() is called anywhere in the object, the rule will be applied to the Name property by executing the StringRequired method. The implementation for this method was covered in 5.

The rule will also be applied if ValidationRules.CheckRules() is called with no parameters, as that causes the validation rules for all properties to be checked.

Other rules are a bit more complex, requiring extra parameter values to operate. This is the case with the StringMaxLength rule, for instance: ValidationRules.AddRule( _ AddressOf Validation.CommonRules.StringMaxLength, _ New Validation.CommonRules.MaxLengthRuleArgs("Name", 50)) Notice that in this case, a MaxLengthRuleArgs object is created, supplying both the name of the property against which the rule is to be run and the maximum length for a valid String. Both of the rules so far have been in the CommonRules class. But Project has a custom rule method as well: StartDateGTEndDate. This rule is associated with both the Started and Ended properties:

ValidationRules.AddRule(AddressOf StartDateGTEndDate, "Started") ValidationRules.AddRule(AddressOf StartDateGTEndDate, "Ended") As you ll see, this custom rule compares the two date values to ensure that the project doesn t end before it begins.