C# 5.0 Programmer's Reference

668 ❘ APPENDIX A Solutions to Exercises
5. You could include the following using directives to define the aliases. (You could use different
names for the aliases.)
using Ord = OrderTracker.OrderTools.OrderClasses;
using Ful = OrderTracker.CustomerTools.Fulfillment;
Code in the Algorithms namespace could then use the following code to define objects with
those aliases.
public Ord.Order order1;
public Ful.Order order2;
6. You could define an alias for the OrderTracker.CustomerTools.Fulfillment class as in
Exercise 5. The code could use the other Order class without any namespace or alias. The
following code shows how the Customer class could define both kinds of objects.
public Order order1;
public Ful.Order order2;
7. The Billing namespace doesn’t define any classes with names that are used elsewhere in
the hierarchy, so you can add the following using directive.
using OrderTracker.CustomerTools.Billing;
Now all code can use the Invoice class without including any namespace information.
8. The most obvious improvement would be to rename the classes so that there are no duplicate
names. Perhaps you could change the name of the Fulfillment namespace’s Order
class to Shipment or PackingList (depending on the purpose of that class).
A second improvement would be to flatten the namespace hierarchy. The hierarchy doesn’t
actually help developers keep the code separate. You can do that just as easily by placing
different pieces of code in separate modules.
Often namespace hierarchies arise because pieces of an application are implemented in different
libraries. The libraries have different namespaces to protect them from name collisions
with the other libraries. In this example, however, it’s unlikely that each namespace represents
a separate library. For example, it’s unlikely that the Fulfillment and Billing code can
work without the Customer class, so they probably weren’t developed as separate libraries.
A final simplification might be to merge the two Order classes into a single class. Whether
that would be better than leaving them as two separate classes depends on how much they
overlap. If they are practically the same class, then merging them would simplify the application.
If they serve different purposes, then it may be better to keep them as separate classes.
Chapter 14
1. The PalindromeChecker example program uses the following code to do this. The key code
is highlighted in bold.
private void palindromeTextBox_TextChanged(object sender, EventArgs e)
{
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