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C# - Loops

In C#, loops are used to execute a block of code repeatedly until a specified condition is met. They are essential for performing repetitive tasks efficiently. C# provides several types of loops, each suited for different scenarios. Here’s an overview of the most commonly used loops in C#:

1. for Loop

The for loop is used when the number of iterations is known beforehand. It consists of three parts: initialization, condition, and iteration.

Syntax:

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

Example:

csharp
for (int i = 0; i < 5; i++)
{
    Console.WriteLine(i); // Prints numbers 0 to 4
}

2. while Loop

The while loop executes a block of code as long as the specified condition is true. The condition is checked before the execution of the loop body.

Syntax:

csharp
while (condition)
{
    // Code to execute
}

Example:

csharp
int i = 0;
while (i < 5)
{
    Console.WriteLine(i); // Prints numbers 0 to 4
    i++;
}

3. do-while Loop

The do-while loop is similar to the while loop but guarantees that the code block will execute at least once, as the condition is checked after the loop body.

Syntax:

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

Example:

csharp
int i = 0;
do
{
    Console.WriteLine(i); // Prints numbers 0 to 4
    i++;
} while (i < 5);

4. foreach Loop

The foreach loop is used to iterate over elements in a collection, such as arrays or lists. It is ideal when you need to access each item in a collection without needing to know the index.

Syntax:

csharp
foreach (var item in collection)
{
    // Code to execute
}

Example:

csharp
string[] names = { "Alice", "Bob", "Charlie" };
foreach (string name in names)
{
{
    Console.WriteLine(name); // Prints each name in the array
}

5. break Statement

The break statement is used to exit a loop prematurely, regardless of the loop condition.

Example:

csharp
for (int i = 0; i < 10; i++)
{
    if (i == 5)
    {
        break; // Exit the loop when i is 5
    }
    Console.WriteLine(i); // Prints numbers 0 to 4
}

6. continue Statement

The continue statement skips the remaining code in the current iteration of the loop and proceeds to the next iteration.

Example:

csharp
for (int i = 0; i < 10; i++)
{
    if (i % 2 == 0)
    {
        continue; // Skip even numbers
    }
    Console.WriteLine(i); // Prints odd numbers from 1 to 9
}

7. Nested Loops

You can nest loops within each other to perform more complex iterations.

Example:

csharp
for (int i = 0; i < 3; i++)
{
    for (int j = 0; j < 3; j++)
    {
        Console.WriteLine($"i = {i}, j = {j}");
    }
}

8. Using Loops with Collections

Loops are often used to iterate over collections such as arrays, lists, or dictionaries.

Example with Array:

csharp
int[] numbers = { 1, 2, 3, 4, 5 };
foreach (int number in numbers)
{
    Console.WriteLine(number); // Prints numbers 1 to 5
}

Example with List:

csharp
List<string> cities = new List<string> { "New York", "London", "Tokyo" };
foreach (string city in cities)
{
{
    Console.WriteLine(city); // Prints each city in the list
}

Example with Dictionary:

csharp
Dictionary<string, int> ages = new Dictionary<string, int>
{
    { "Alice", 30 },
    { "Bob", 25 },
    { "Charlie", 35 }
};

foreach (KeyValuePair<string, int> entry in ages)
{
    Console.WriteLine($"{entry.Key}: {entry.Value}"); // Prints name and age
}

Summary

Loops in C# are powerful constructs for executing code repeatedly. The for loop is ideal for scenarios with a known number of iterations, while the while and do-while loops are useful when the number of iterations is not known in advance. The foreach loop simplifies iterating over collections. Understanding how to use break and continue statements effectively can help control loop execution. Nested loops and loop operations with collections further enhance the versatility of loops in C#.