C# 4 and .NET 4

42 ❘ ChaPTer 2 cOre c#
}
}
}
}
{
Console.Write(" " + j);
}
Console.WriteLine();
code snippet NestedFor.cs
Although j is an integer, it will be automatically converted to a string so that the concatenation can take place.
The preceding sample results in this output:
0 1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19
20 21 22 23 24 25 26 27 28 29
30 31 32 33 34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49
50 51 52 53 54 55 56 57 58 59
60 61 62 63 64 65 66 67 68 69
70 71 72 73 74 75 76 77 78 79
80 81 82 83 84 85 86 87 88 89
90 91 92 93 94 95 96 97 98 99
Although it is technically possible to evaluate something other than a counter variable in a for loop’s test
condition, it is certainly not typical. It is also possible to omit one (or even all) of the expressions in the for
loop. In such situations, however, you should consider using the while loop.
The while loop
Like the for loop, while is a pretest loop. The syntax is similar, but while loops take only one expression:
while(condition)
statement(s);
Unlike the for loop, the while loop is most often used to repeat a statement or a block of statements for a
number of times that is not known before the loop begins. Usually, a statement inside the while loop’s body will
set a Boolean flag to false on a certain iteration, triggering the end of the loop, as in the following example:
bool condition = false;
while (!condition)
{
// This loop spins until the condition is true.
DoSomeWork();
condition = CheckCondition(); // assume CheckCondition() returns a bool
}
The do . . . while loop
The do...while loop is the post-test version of the while loop. This means that the loop’s test condition
is evaluated after the body of the loop has been executed. Consequently, do...while loops are useful for
situations in which a block of statements must be executed at least one time, as in this example:
bool condition;
do
{
// This loop will at least execute once, even if Condition is false.
MustBeCalledAtLeastOnce();
condition = CheckCondition();
} while (condition);
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