Exercise: Loop over all of the controls on a form to validate them

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The answer to the exercise will be included and explained if you attend the Wise Owl course listed below!

Category ==> Visual Basic 2010  (42 exercises)
Topic ==> Loops  (2 exercises)
Level ==> Average difficulty
Course ==> Introduction to VB.NET
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help).

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Press CTRL + D to add the file called frmApplication.vb from the above folder into your project (or right click on the project and choose to add it as an existing item). 

Change your project's properties to make this the default form for your project.  When you run your project, you should see this:

Application form for dating agency

For the exercise you'll add code to this button to validate all of the input boxes.

Sadly you can't just loop over all of the controls on the form, because some of them are hidden in the two group boxes.  Because of this you need a different algorithm - a suggestion is shown overleaf.

Here's a suggestion for how to solve our problem:

'FOR EACH CONTROL ON THE FORM

 

'IF IT'S A GROUPBOX (that is, if TYPEOF G IS GROUPBOX)

 

'FOR EACH CONTROL IN THE COLLECTION OF CONTROLS

'WITHIN THIS GROUPBOX g

 

'CHECK THIS CONTROL ISN'T A LABEL (NOT INTERESTED

'IN THESE)

 

'IF THE LENGTH OF THIS CONTROL IS 0, SET THE

'FOCUS TO THIS CONTROL AND REPORT ERROR

When you've written your code (!), check it works, then close down your application and form.

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