Visual Basic.NET How to Program (PDF)

674 Strings, Characters and Regular Expressions Chapter 15
Fig. 15.22 Validating user information using regular expressions (part 5 of 5).
When a user clicks the OK button, the program checks to make sure that none of the
fields are empty (lines 36–39). If one or more fields are empty, the program signals the user
that all fields must be filled before the program can validate the input information (lines
42–43). Line 46 calls instance method Focus of class TextBox. Method Focus places
the cursor within the TextBox that made the call. The program then exits the event handler
(line 48). If there are no empty fields, the user input is validated. The Last Name is
validated first (lines 52–60). If it passes the test (i.e., if the Success property of the
Match instance is True), control moves on to validate the First Name (lines 63–71).
This process continues until all TextBoxes are validated, or until a test fails (Success
is False) and the program sends an appropriate error message. If all fields contain valid
information, success is signaled, and the program quits.