Beginning ASP.NET 4.5 in CSharp and VB Opsylum

776 x APPENDIX A EXERCISE ANSWERS
Exercise 2 Solution
If you don’t inspect the IsValid property, your system is vulnerable to invalid data. Users can disable
JavaScript in their browsers and submit invalid data directly into your page. By checking the
IsValid property you can tell whether or not it’s safe to continue with the submitted data.
Exercise 3 Solution
The From property of the MailMessage class is of type MailAddress, meaning that you can directly
assign a single instance of this class to it. Because you can potentially have more than one recipient,
the To property is a collection of MailAddress objects, and so you need to use its Add method to
add instances of MailAddress to it.
Exercise 4 Solution
To call a client-side validation function, you need to set the ClientValidationFunction property
of the CustomValidator like this:
*
The client function that you need to add to the markup of the page must have the following
signature:
function functionName(source, args)
{ ... }
The source argument contains a reference to the actual CustomValidator control in the client-side
HTML code. The args argument provides context information about the data and enables you to
indicate whether or not the data is valid. The names of the arguments don’t have to be source and
args; however, when using these names, the client-side function looks as close to its server-side
counterpart as possible. Another common naming scheme, used for almost all other event handlers
in ASP.NET, is to use sender and e, respectively.
Exercise 5 Solution
To tell the validation mechanism whether the data you checked is valid, you set the IsValid property
of the args argument in your custom validation method. This applies to both client- and serverside
code. The following snippet shows how this is done in the client-side validation method for the
ContactForm.ascx control:
if (phoneHome.value != '' || phoneBusiness.value != '')
{
args.IsValid = true;
}
else
{
args.IsValid = false;
}