Control Structures if-else, switch, loops (for, while, do-while)

Control Structures in C# 🚀

Control structures help control the flow of execution in a program. C# provides conditional statements (if-else, switch) and loops (for, while, do-while) to handle different scenarios.

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1️⃣ Conditional Statements

🔹 if-else Statement

The if-else statement executes code based on conditions.

Syntax:

if (condition)
{
    // Code runs if condition is true
}
else if (anotherCondition)
{
    // Code runs if anotherCondition is true
}
else
{
    // Code runs if none of the above conditions are true
}

Example:

int age = 20;
if (age >= 18)
{
    Console.WriteLine("You are an adult.");
}
else
{
    Console.WriteLine("You are a minor.");
}

✅ Nested if-else

int number = 10;
if (number > 0)
{
    if (number % 2 == 0)
    {
        Console.WriteLine("Positive Even Number");
    }
    else
    {
        Console.WriteLine("Positive Odd Number");
    }
}

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🔹 switch Statement

The switch statement is an alternative to multiple if-else conditions, used when checking multiple values for a variable.

Syntax:

switch (variable)
{
    case value1:
        // Code for value1
        break;
    case value2:
        // Code for value2
        break;
    default:
        // Code if no match
        break;
}

Example:

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

✅ Using switch with enum

enum Colors { Red, Green, Blue }
Colors myColor = Colors.Green;

switch (myColor)
{
    case Colors.Red:
        Console.WriteLine("Selected Red");
        break;
    case Colors.Green:
        Console.WriteLine("Selected Green");
        break;
    case Colors.Blue:
        Console.WriteLine("Selected Blue");
        break;
}

✅ Using switch expression (C# 8+)

int number = 2;
string result = number switch
{
    1 => "One",
    2 => "Two",
    3 => "Three",
    _ => "Unknown"
};
Console.WriteLine(result);

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2️⃣ Loops in C#

Loops allow executing repetitive tasks until a condition is met.

🔹 for Loop

The for loop is used when the number of iterations is known.

Syntax:

for (initialization; condition; update)
{
    // Code to execute
}

Example:

for (int i = 1; i <= 5; i++)
{
    Console.WriteLine("Iteration: " + i);
}

✅ Looping through an array

string[] fruits = { "Apple", "Banana", "Cherry" };
for (int i = 0; i < fruits.Length; i++)
{
    Console.WriteLine(fruits[i]);
}

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🔹 while Loop

The while loop executes as long as the condition remains true.

Syntax:

while (condition)
{
    // Code to execute
}

Example:

int count = 1;
while (count <= 3)
{
    Console.WriteLine("Count: " + count);
    count++;
}

✅ Using while to read user input

string input = "";
while (input != "exit")
{
    Console.WriteLine("Enter a word (type 'exit' to stop): ");
    input = Console.ReadLine();
}

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🔹 do-while Loop

The do-while loop executes the block at least once, even if the condition is false.

Syntax:

do
{
    // Code to execute
} while (condition);

Example:

int num = 1;
do
{
    Console.WriteLine("Number: " + num);
    num++;
} while (num <= 3);

✅ Using do-while for menu selection

int option;
do
{
    Console.WriteLine("1. Start");
    Console.WriteLine("2. Stop");
    Console.WriteLine("3. Exit");
    Console.Write("Enter option: ");
    option = Convert.ToInt32(Console.ReadLine());
} while (option != 3);

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3️⃣ Loop Control Statements

✅ break Statement - Exits the loop immediately
✅ continue Statement - Skips the current iteration and moves to the next one

Example (break):

for (int i = 1; i <= 5; i++)
{
    if (i == 3)
        break; // Stops loop when i is 3
    Console.WriteLine(i);
}

Example (continue):

for (int i = 1; i <= 5; i++)
{
    if (i == 3)
        continue; // Skips iteration when i is 3
    Console.WriteLine(i);
}

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🔚 Summary

• ✅ if-else is used for conditional execution
• ✅ switch is used for checking multiple cases
• ✅ for loop is best for fixed iterations
• ✅ while loop is best for unknown iterations
• ✅ do-while loop ensures at least one execution
• ✅ Loop control statements (break, continue) alter loop flow