Learning C#

Iteration (Looping) Statements

There are many situations in which you will want to do the same thing again and again, perhaps slightly changing a value each time you repeat the action. This is called iteration or looping. Typically, you’ll iterate (or loop) over a set of items, taking the same action on each. This is the programming equivalent of an assembly line. On an assembly line, you might take a hundred car bodies and put a windshield on each one as it comes by. In an iterative program, you might work your way through a collection of text boxes on a form, retrieving the value from each in turn and using those values to update a database.

C# provides an extensive suite of iteration statements, including for and while, and also do...while and foreach loops. You can also create a loop by using the goto statement. The remainder of this chapter considers the use of goto, for, while, and do...while. However, you’ll have to wait until Chapter 15 to learn more about foreach.

Creating Loops with goto

The goto statement was used previously as an unconditional branch in a switch statement. Its more common usage, however, is to create a loop. In fact, the goto statement is the seed from which all other looping statements have been germinated. Unfortunately, it is a semolina seed, producer of spaghetti code and endless confusion.

Programs that use goto statements outside of switch blocks jump around a great deal. Goto can cause your method to loop back and forth in ways that are difficult ...