May 2010
Beginner to intermediate
551 pages
18h 34m
English
Content preview from Stephens' C# Programming with Visual Studio® 2010 24-Hour Trainer
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256
LESSON 21 Handling Errors
FIGURE 211
Lesson Requirements
Copy the program you built in Lesson 19, Exercise 4 (or download Lesson 19’s version from
the book’s web site).
The previous version of this program uses repeated code to perform calculations when the
user clicks either Calculate or OK. Move that code into a new ValuesAreOk method that
validates the user’s inputs. In addition to protecting the form from format errors, the func-
tion should verify that:
Item name is not blank.
Price Each > 0.
Quantity > 0.
If
ValuesAreOk finds a problem, it should:
Tell the user.
Set focus to the textbox that caused the problem.
Return
false.
If
ValuesAreOk finds that all of the values are okay, it should return true.
Hints
If the user clicks the OK button, the form should close only if the user’s inputs are valid. Be
sure the OK button’s DialogResult property doesn’t automatically close the form.
Use
try-catch blocks to protect against format errors.
Step-by-Step
Copy the program you built in Lesson 19, Exercise 4 (or download Lesson 19’s version from
the book’s web site).
1. This is straightforward.
596906book.indd 256 4/8/10 7:40:27 AM
Try It
257
The previous version of this program uses repeated code to perform calculations when the
user clicks either Calculate or OK. ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.