Break statement in C#

The break statement in C# has following two usage:

1. When the break statement is encountered inside a loop, the loop is immediately terminated and program control resumes at the next statement following the loop.
2. It can be used to terminate a case in the switch statement.

If you are using nested loops (i.e., one loop inside another loop), the break statement will stop the execution of the innermost loop and start executing the next line of code after the block.

Syntax:

The syntax for a break statement in C# is as follows:

break;

Flow Diagram:

Example:

using System;
 


namespace break_statement

{
 

class Program

{

static void Main(string[] args)
      

{
        

int i = 0;
 
        

while (i < 100)
         

{
           

Console.WriteLine(i);
           

if (i == 20)
            

{
              

Console.WriteLine("breaking the current segment...");
              break;
            

}
           

i++;
         

}  
        

Console.ReadLine();
     

 }
  

 }


}

When the above code is compiled and executed, it produces the following result:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
breaking the current segment

Nested Loop in C#

C# allows to use one loop inside another loop. Following section shows few examples to illustrate the concept.

Syntax:

The syntax for a nested for loop statement in C# is as follows:

for ( init; condition; increment )
{
   for ( init; condition; increment )
   {
      statement(s);
   }
   statement(s);
}

The syntax for a nested while loop statement in C# is as follows:

while(condition)
{
   while(condition)
   {
      statement(s);
   }
   statement(s);
}

The syntax for a nested do...while loop statement in C# is as follows:

do
{
   statement(s);
   do
   {
      statement(s);
   }while( condition );

}while( condition );

A final note on loop nesting is that you can put any type of loop inside of any other type of loop. For example a for loop can be inside a while loop or vice versa.

Example:

The following program uses a nested for loop to find the prime numbers from 2 to 100:

using System;

namespace Loops
{
    
   class Program
   {
      static void Main(string[] args)
      {
         /* local variable definition */
         int i, j;

         for (i = 2; i < 100; i++)
         {
            for (j = 2; j <= (i / j); j++)
               if ((i % j) == 0) break; // if factor found, not prime
            if (j > (i / j)) 
               Console.WriteLine("{0} is prime", i);
         }

         Console.ReadLine();
      }
   }
} 

When the above code is compiled and executed, it produces the following result:

2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime

Do-While Loop in C#

Unlike for and while loops, which test the loop condition at the top of the loop, the do...while loop checks its condition at the bottom of the loop.

A do...while loop is similar to a while loop, except that a do...while loop is guaranteed to execute at least one time.

Syntax:

The syntax of a do...while loop in C# is:

do
{
   statement(s);

}while( condition );

Notice that the conditional expression appears at the end of the loop, so the statement(s) in the loop execute once before the condition is tested.

If the condition is true, the flow of control jumps back up to do, and the statement(s) in the loop execute again. This process repeats until the given condition becomes false.

Flow Diagram:

Example:

using System;

namespace do_while

{
 

class Program
  

{
     

static void Main(string[] args)
      

{
 

 int table,i,res;
       

 table=12;
       

 i=1;
       

 do
         

{
          

 res = table * i;
         

 Console.WriteLine("{0} x {1} = {2}", table, i, res);
          

 i++;
         

}
 // must put semi-colon(;) at the end of while               condition in do...while loop.
       

 while (i <= 10);
 
       

 Console.ReadLine();
      

}
  

 }

}

When the above code is compiled and executed, it produces the following result:

12 x 1 = 12
12 x 2 = 24
12 x 3 = 36
12 x 4 = 48
12 x 5 = 60
12 x 6 = 72
12 x 7 = 84
12 x 8 = 92
12 x 9 = 108
12 x 10 = 120 

For Loop in C#

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 incrementstatement. 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 condition). After the condition becomes false, the for loop terminates.

Flow Diagram:

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