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 item in the collection. 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
while, and also
foreach loops. You can also create a loop by
goto statement. The
remainder of this chapter considers the use of
do...while. However, we’ll postpone coverage
foreach until Chapter 10.
was used earlier in this chapter as an unconditional branch in a
switch statement. The more common
goto, however, is to create
a loop. In fact, the
is the seed from which all other looping statements have been germinated. Unfortunately, it is a semolina
seed, producer of "spaghetti code" (see
the following sidebar) and endless confusion.