Vb net validating event not firing how to build trust in a dating relationship
A problem with this approach is that if the users enter an invalid value and tries to close the application, by default, they won't be able to do it. NET 2.0, we have the Auto Validate property on the Form class that lets you specify exactly what the behavior should be when the validation error occurs at the control level.The Auto Validate property may have four values: Disable, Enable Prevent Focus Change, Enable Allow Focus Change, Inherit. If you set Enable Prevent Focus Change value and Cancel is set to true, focus will remain on the control that failed the validation.The Validating event is the one that handles most of the validation logic.This event defines an event argument (Cancel Event Args) which contains the Boolean property named Cancel to set a signal that the event being fired should not be completed.Should this validation be done in the business layer or in the middleware component of a multi-layer application?Some checks are business rules and thus conceptually they must be done in the business layer of the multi-layer application or in the server-side of a client/server application.
If you don't validate input, your application can represent a serious security hole on the system.
This eliminates the possibility the end-users will incorrectly enter the values.
The refining of the data is done later, when the data is passed to another layer for processing.
The Windows Forms library includes an Error Provider control, which can be used to display messages, icons, and other information in response to data entry errors. The Common Language Runtime and your code can throw exceptions within an application, across languages, and across machines. NET provides a structured method for handling exceptions with the use of the Try, Catch, Finally, and Throw statements. NET Framework Class Library provides a huge set of exception classes to deal with various unforeseen or unusual conditions in the normal execution environment.
This exam objective covers the Error Provider control and various other input validation techniques. NET Framework adopts the Windows structured exception handling model. If you feel the need to create custom Exception classes to meet specific requirements of your application, you can derive from the Application Exception class.
But the key components, which the end-users interact with, are those which reside in the presentation layer.