C# Loops

Loops repeat a block of code while a condition is true, so you can do the same task many times with little code.

The while Loop

Example

csharp

int bottles = 3;

while (bottles > 0)
{
    Console.WriteLine($"{bottles} bottles left");
    bottles--;
}
Console.WriteLine("All sold!");

Output

3 bottles left
2 bottles left
1 bottles left
All sold!

The do...while Loop

The body runs once before the condition is checked:

Example

csharp

string answer;
do
{
    Console.Write("Type yes to continue: ");
    answer = Console.ReadLine();
} while (answer != "yes");

Console.WriteLine("Thank you!");

Output

Type yes to continue: no
Type yes to continue: yes
Thank you!

The for Loop

Example

text

for (start; condition; step)
{
    // code to repeat
}

Example

csharp

for (int i = 1; i <= 5; i++)
{
    Console.WriteLine($"12 x {i} = {12 * i}");
}

Output

12 x 1 = 12
12 x 2 = 24
12 x 3 = 36
12 x 4 = 48
12 x 5 = 60

The foreach Loop

foreach goes through every item of an array or list:

Example

csharp

string[] subjects = { "English", "Urdu", "Maths", "Computer" };

foreach (string subject in subjects)
{
    Console.WriteLine(subject);
}

Output

English
Urdu
Maths
Computer

You cannot change the loop variable inside a foreach. If you need to change items, use a for loop with an index.

break and continue

Statement	What it does
`break`	Leaves the loop immediately
`continue`	Skips to the next round

Example

csharp

for (int n = 1; n <= 10; n++)
{
    if (n == 3)
    {
        continue;   // skip 3
    }
    if (n == 6)
    {
        break;      // stop at 6
    }
    Console.Write(n + " ");
}
Console.WriteLine();

Output

1 2 4 5

Building a Total

Example

csharp

int[] dailySales = { 4500, 3200, 5100, 2800, 6000 };
int total = 0;

foreach (int sale in dailySales)
{
    total += sale;
}

Console.WriteLine($"Weekly total: Rs {total}");

Output

Weekly total: Rs 21600

Printing a Pattern

Loops are often used to print patterns. Here each round prints one more star:

Example

csharp

for (int row = 1; row <= 3; row++)
{
    Console.WriteLine(new string('*', row));
}

Output

*
**
***

Here new string('*', row) builds a string with row stars, so no inner loop is needed. Look for helpers like this before writing nested loops.

Exercise

Which loop is made for going through each item in a collection?

whiledo...whileforeachswitch