Implementing Business Logic - ASP.NET Dynamic Data - page 297

The new version of the FulfillButton_Click event handler wraps a try/catch block
around the FulfillOrder and SaveChanges method calls, which could throw validation
exceptions. The catch block intercepts all exceptions and passes them to the
HandleException method of the UnleashedValidator (defined at the top of the page
in Listing 9.3). If the HandleException method returns false , the code re-throws the
exception.
As discussed in Chapter 8, the UnleashedValidator class inherits from the built-in
DynamicValidator and extends error handling to support AggregateException . The
HandleException method receives an Exception object as a parameter, iterates over all
UnleashedValidator controls on the page, including those in field templates, and
attempts to handle the exception by passing it to each validator's ValidateException
method. The HandleException returns true if one or more validators on the page were
able to handle the exception by setting their ValidationException properties. For
complete details, please refer to the UnleashedValidator source code in the
Unleashed.DynamicData project accompanying the topic.
Figure 9.8 shows an example of an error message displayed because of the
ValidationException thrown in the FulfillOrder business rule method.
FIGURE 9.8 Validation error from calling a business rule method.