C# 2008 Programmer's Reference

with a break keyword to jump out of the switch block. The default keyword defines the block that will be executed if none of the preceding conditions is met.

The following example shows multiple statements in a case statement:

string symbol = 'MSFT';
switch (symbol) {
case 'MSFT':
 Console.Write('Stock price for MSFT: ');
 Console.WriteLine(27.96);
 break;
case 'GOOG':
 Console.Write('Stock price for GOOG: ');
 Console.WriteLine(437.55);
 break;
case 'YHOO':
 Console.Write('Stock price for YHOO: ');
 Console.WriteLine(27.15);
 break;
default:
 Console.WriteLine('Stock symbol not recognized');
 break;
}

In C#, fall-throughs are not allowed; that is, each case block of code must include the break keyword so that execution can be transferred out of the switch block (and not 'fall through' the rest of the case statements). However, there is one exception to this rule — when a case block is empty. Here's an example:

string symbol = 'INTC';
switch (symbol) {
case 'MSFT':
 Console.WriteLine(27.96);
 break;
case 'GOOG':
 Console.WriteLine(437.55);
 break;
case 'INTC':
case 'YHOO':
 Console.WriteLine(27.15);
 break;
default:
 Console.WriteLine('Stock symbol not recognized');
 break;
}

The case for 'INTC' has no execution block/statement and hence the execution will fall through into the case for 'YHOO', which will incorrectly print the output '27.15'. In this case, you need to insert a break statement after the 'INTC' case to prevent the fall-through:

switch (symbol) {
case 'MSFT':
 Console.WriteLine(27.96);
 break;
case 'GOOG':
 Console.WriteLine(437.55);
 break;
case 'INTC':
 break;
case 'YHOO':
 Console.WriteLine(27.15);
 break;
default:
 Console.WriteLine('Stock symbol not recognized');
 break;
}

Looping

A loop is a statement, or set of statements, repeated for a specified number of times or until some condition is met. C# supports the following looping constructs:

□ for

□ foreach

□ while and do-while

for Loop

The for loop executes a statement (or a block of statements) until a specified expression evaluates to false. The for loop has the following format:

for (statement; expression; statement(s)) {
 //---statement(s)
}

The expression inside the for loop is evaluated first, before the execution of the loop. Consider the following example:

int[] nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
for (int i=0; i<9; i++) {
 Console.WriteLine(nums[i].ToString());
}

Here, nums is an integer array with nine members. The initial value of i is 0 and after each iteration it increments by 1. The loop will continue as long as i is less than 9. The loop prints out the numbers from the array:

1
2
3
4
5
6
7