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Unit-2

Control Statements in c#

A control statement in java is a statement that determines whether the other statements will be executed or not. It controls the flow of a program. Control Statements can be divided into three categories, namely

●        Decision Making statements

●        Iteration (Looping) statements

●        Jump statements

⮚  Decision Making statements

Decision making statements help you to make decision based on certain conditions. These conditions are specified by a set of decision making statements having boolean expressions which are evaluated to a boolean value true or false. There are following types of decision making statements in C#.

1) Simple if statement:  It is the most basic statement among all control flow statements in C#. It evaluates a Boolean expression and enables the program to enter a block of code if the expression evaluates to true.

Syntax:

if(boolean_expression) {

   /* statement(s) will execute if the boolean expression is true */

}

Flow Diagram



Example

using System;

 

namespace DecisionMaking {

   class Program {

      static void Main(string[] args) {

         /* local variable definition */

         int a = 10;

       

         /* check the boolean condition using if statement */

         if (a < 20) {

            /* if condition is true then print the following */

            Console.WriteLine("a is less than 20");

         }

         Console.WriteLine("value of a is : "+ a);

      }

   }

}

Output

a is less than 20;

value of a is : 10

 

2) if else statement

If else  is an extension to the if-statement, which uses another block of code, i.e., else block. The else block is executed if the condition of the if-block is evaluated as false.

 

Syntax:

if(boolean_expression) {

   /* statement(s) will execute if the boolean expression is true */

} else {

   /* statement(s) will execute if the boolean expression is false */

}

 


using System;

 

namespace DecisionMaking {

   class Program {

      static void Main(string[] args) {

         /* local variable definition */

         int a = 100;

        

         /* check the boolean condition */

         if (a < 20) {

            /* if condition is true then print the following */

            Console.WriteLine("a is less than 20");

         } else {

            /* if condition is false then print the following */

            Console.WriteLine("a is not less than 20");

         }

         Console.WriteLine("value of a is : {0}", a);

      }

   }

}

Output

a is not less than 20;

value of a is : 100

 Nested IF

In C#, nested if statements are if statements placed inside another if or else block. This is useful when you want to check multiple conditions in a hierarchical or dependent way.

 

Syntax of Nested if in C#:

if (condition1)
{
    // Executes if condition1 is true
    if (condition2)
    {
        // Executes if both condition1 and condition2 are true
    }
    else
    {
        // Executes if condition1 is true but condition2 is false
    }
}
else
{
    // Executes if condition1 is false
}

 

FLOW DIAGRAM


Example:

using System;
class Program
{
    static void Main()
    {
        int age = 20;
        string citizenship = "Nepali";
        if (age >= 18)
        {
            if (citizenship == "Nepali")
            {
                Console.WriteLine("You are eligible to vote.");
            }
            else
            {
                Console.WriteLine("You are not a Nepali citizen.");
            }
        }
        else
        {
            Console.WriteLine("You are underage.");
        }
    }
}

 if-else if Ladder in C#
The if-else if ladder in C# is used when you have multiple conditions 
to test, one after another. Only the first true condition will be executed,
 and the rest will be skipped.
Syntax:
if (condition1)
{
    // Code if condition1 is true
}
else if (condition2)
{
    // Code if condition2 is true
}
else if (condition3)
{
    // Code if condition3 is true
}
else
{
    // Code if none of the above conditions are true
}




Example: Grading System
using System;
class Program
{
    static void Main()
    {
        int marks = 75;
        if (marks >= 90)
        {
            Console.WriteLine("Grade: A+");
        }
        else if (marks >= 80)
        {
            Console.WriteLine("Grade: A");
        }
        else if (marks >= 70)
        {
            Console.WriteLine("Grade: B");
        }
        else if (marks >= 60)
        {
            Console.WriteLine("Grade: C");
        }
        else
        {
            Console.WriteLine("Fail");
        }
    }
}

 Switch Statement

The switch statement is a control statement that executes one block of code
 among many options based on the value of a variable.


Syntax Of Switch Statement:
switch (expression)
{
    case value1:
        // Code block
        break;

    case value2:
        // Code block
        break;

    default:
        // Default code block
        break;
}



Flow diagram


Example:
using System;
namespace program{

public class SwitchStatement{
static void Main(string[] args){
int day = 3;

switch (day)
{
    case 1:
        Console.WriteLine("Sunday");
        break;
    case 2:
        Console.WriteLine("Monday");
        break;
    case 3:
        Console.WriteLine("Tuesday");
        break;
    default:
        Console.WriteLine("Invalid day");
        break;
}

}
}
}



 nested switch
A nestedswitch means using a switch statement inside another switch.
It's useful when you want to perform different actions based on multiple
conditions.
int category = 1;
int item = 2;

switch (category)
{
    case 1:
        Console.WriteLine("Fruits");
        switch (item)
        {
            case 1:
                Console.WriteLine("Apple");
                break;
            case 2:
                Console.WriteLine("Banana");
                break;
            default:
                Console.WriteLine("Unknown Fruit");
                break;
        }
        break;

    case 2:
        Console.WriteLine("Vegetables");
        switch (item)
        {
            case 1:
                Console.WriteLine("Carrot");
                break;
            case 2:
                Console.WriteLine("Potato");
                break;
            default:
                Console.WriteLine("Unknown Vegetable");
                break;
        }
        break;

    default:
        Console.WriteLine("Unknown Category");
        break;
}








⮚   
Looping



In programming, sometimes we need to execute the block of
code repeatedly while some condition evaluates to true. Loop statements are
used to execute the set of instructions in a repeated order. 
The execution of
the set of instructions depends upon a particular condition.
     
  1. for loop
    2.  
  2. while loop
    3.  
  3. do-while loop
    4.  
  4. nested  loop



1.  For Loop
For Loop is entry controlled loop. It enables us to initialize the
 loop variable, check the condition, and increment/decrement
in a single line of code. We use the for loop only when we
 exactly know the
number of times, we want to execute the block of code.



Syntax: 


for(initialization, condition, increment/decrement) {    


//block of statements    


}


Example: 


// C# program to illustrate for loop.
using System;
class ForLoop
{
            public static void Main()
            {


 for(int i = 1; i <= 5; i++)
 Console.WriteLine("Hello Computer Engineering Students");
   }
}



2. While Loop
·        
It is called an entry-controlled
loop because the condition is checked before the loop
body executes.
·        
Used when
the number of iterations is not known in advance.
·    
Initialization is
done before the loop, and increment/decrement is done inside
the loop body.



 Syntax:
while (condition)
{
    // statements
}


 Example:
using System;
class whileLoopDemo
{
    public static void Main()
    {
        int x = 1;
        while (x <= 4)
        {
            Console.WriteLine("Hello Computer Engineering Students");
            x++;
        }
    }
}





3. Do-While Loop
·        
It is an exit-controlled
loop as the condition is checked after the loop
executes.
·        
It executes
at least once, even if the condition is false.
·       
Best used when
you want to ensure the loop runs at least once.


Syntax:
do
{
    // statements
}
while (condition);


 Example:
using System; 
class dowhileloopDemo
{
    public static void Main()
    {
        int x = 10;
        do
        {
            Console.WriteLine("Hello Computer Engineering Students");
            x++;
        }
        while (x < 9);
    }
}



Output:
Hello Computer Engineering Students

 Jump Statements in C#
Jump statements are used to change the normal flow of execution.

They are useful for breaking or skipping loop iterations.



 1. Break Statement
·      
Exits the current loop or switch.
·        
The control jumps to the first statement after the loop.



 Example:
using System;
namespace MyApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 0; i < 10; i++)
            {
                if (i == 4)
                {
                    break;
                }
                Console.WriteLine(i);
            }
        }
    }
}



 Output: 
0
1
2
3
 2. Continue Statement
·        
Skips the current iteration and moves to the next iteration.
·        
Loop does not break, only skips the remaining code for the
 current pass.



 Example:
using System;
namespace MyApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            for (int i = 1; i < 6; i++)
            {
                if (i == 3)
                {
                    continue;
                }
                Console.WriteLine(i);
            }
        }
    }
}


 Output:
1
2
4
5

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