34,333
edits
Changes
New page: The C# ''for'' loop described in C# Looping - The for Statement previously works well when you know in advance how many times a particular task need...
The C# ''for'' loop described in [[C Sharp Looping - The for Statement|C# Looping - The for Statement]] previously works well when you know in advance how many times a particular task needs to be repeated in a program. There will, however, be instances where code needs to be repeated until a certain condition is met, with no way of knowing in advance how many repetitions are going to be needed to meet that criteria. To address this C#, provides the ''while'' loop (yet another construct inherited by C# from the C Programming Language)
== The C# while Loop ==
Essentially, the ''while'' loop repeats a set of tasks until a specified condition is met. The ''while'' loop syntax is defined follows:
<pre>
while (''condition'')
{
// C# statements go here
}
</pre>
where ''condition'' is an expression that will return either ''true'' or ''false'' and the ''// C# statements go here'' comment represents the C# code to be executed while the ''condition'' expression is ''true''. For example:
<pre>
int myCount = 0;
while ( myCount < 100 )
{
myCount++;
}
</pre>
In the above example the ''while'' expression will evaluate whether the ''myCount'' variable is less than 100. If it is already greater than 100 the code in the braces is skipped and the loop exits without performing any tasks. If, on the other hand, ''myCount'' is not greater than 100 the code in the braces is executed and the loop returns to the ''while'' statement and repeats the evaluation of ''myCount''. This process repeats until the value of ''myCount'' is greater than 100, at which point the loop exits.
=== C# do ... while loops ===
It is often helpful to think of the ''do ... while'' loop as an inverted ''while'' loop. The ''while'' loop evaluates an expression before executing the code contained in the body of the loop. If the expression evaluates to ''false'' on the first check then the code is not executed. The ''do .. while'' loop, on the other hand, is provided for situations where you know that the code contained in the body of the loop will ''always'' need to be executed at least once. For example, you may want to keep stepping through the items in an array until a specific item is found. You know that you have to at least check the first item in the array to have any hope of finding the entry you need. The syntax for the ''do ... while'' loop is as follows:
<pre>
do
{
// C# statements here
} while (''conditional expression'')
</pre>
In the ''do ... while'' example below the loop will continue until the value of a variable named i equals 0:
<pre>
int i = 10;
do
{
i--;
} while (i > 0)
</pre>
== The C# while Loop ==
Essentially, the ''while'' loop repeats a set of tasks until a specified condition is met. The ''while'' loop syntax is defined follows:
<pre>
while (''condition'')
{
// C# statements go here
}
</pre>
where ''condition'' is an expression that will return either ''true'' or ''false'' and the ''// C# statements go here'' comment represents the C# code to be executed while the ''condition'' expression is ''true''. For example:
<pre>
int myCount = 0;
while ( myCount < 100 )
{
myCount++;
}
</pre>
In the above example the ''while'' expression will evaluate whether the ''myCount'' variable is less than 100. If it is already greater than 100 the code in the braces is skipped and the loop exits without performing any tasks. If, on the other hand, ''myCount'' is not greater than 100 the code in the braces is executed and the loop returns to the ''while'' statement and repeats the evaluation of ''myCount''. This process repeats until the value of ''myCount'' is greater than 100, at which point the loop exits.
=== C# do ... while loops ===
It is often helpful to think of the ''do ... while'' loop as an inverted ''while'' loop. The ''while'' loop evaluates an expression before executing the code contained in the body of the loop. If the expression evaluates to ''false'' on the first check then the code is not executed. The ''do .. while'' loop, on the other hand, is provided for situations where you know that the code contained in the body of the loop will ''always'' need to be executed at least once. For example, you may want to keep stepping through the items in an array until a specific item is found. You know that you have to at least check the first item in the array to have any hope of finding the entry you need. The syntax for the ''do ... while'' loop is as follows:
<pre>
do
{
// C# statements here
} while (''conditional expression'')
</pre>
In the ''do ... while'' example below the loop will continue until the value of a variable named i equals 0:
<pre>
int i = 10;
do
{
i--;
} while (i > 0)
</pre>
