Loop
C# provides following types of loop to handle looping requirements. Click the following links to check their detail.
Loop Type Description
while loop It repeats a statement or a group of statements while a given condition is true. It tests the condition before executing the loop body.for loop It executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.
do...while loop It is similar to a while statement, except that it tests the condition at the end of the loop body
nested loops You can use one or more loops inside any another while, for or do..while loop.
While Loop
A while loop statement in C# repeatedly executes a target statement as long as a given condition is true.
Syntax The syntax of a while loop in C# is:
while(condition)
{
statement(s);
}
Here, statement(s) may be a single statement or a block of statements. The condition may be any expression, and true is any non-zero value. The loop iterates while the condition is true. When the condition becomes false, program control passes to the line immediately following the loop.
using System;
namespace Loops
{
class Program
{
static void Main(string[] args)
{
/* local variable definition */
int a = 10;
/* while loop execution */
while (a < 20)
{
Console.WriteLine("value of a: {0}", a);
a++;
}
Console.ReadLine();
}
}
}
code output
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19
For Loop
A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.
Syntax
The syntax of a for loop in C# is:
for ( init; condition; increment )
{
statement(s);
}
Here is the flow of control in a for loop:
1. The init step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears. 2. Next, the condition is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and flow of control jumps to the next statement just after the for loop.
3. After the body of the for loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition.
4. The condition is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then increment step, and then again testing for a condition). After the condition becomes false, the for loop terminates.
Example
using System;
namespace Loops
{
class Program
{
static void Main(string[] args)
{
/* for loop execution */
for (int a = 10; a < 20; a = a + 1)
{
Console.WriteLine("value of a: {0}", a);
}
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result:
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19
