A Complete Guide - Loop Controls in C#

Loop Controls in C#

1. For Loop

The for loop is commonly used when the number of iterations is known beforehand. It consists of three main parts: initialization, condition, and increment/decrement.

Syntax:

for(initialization; condition; increment/decrement){
    // Code to be executed
}

Example:

for(int i = 0; i < 5; i++){
    Console.WriteLine("Iteration: " + i);
}
// Output: Iteration: 0, Iteration: 1, Iteration: 2, Iteration: 3, Iteration: 4

Explanation:

• Initialization: int i = 0; sets the starting point.
• Condition: i < 5; defines whether the loop should continue or not.
• Increment/Decrement: i++ increments the loop variable i after each iteration.

2. While Loop

The while loop repeats a block of code as long as a specified condition is true.

Syntax:

while(condition){
    // Code to be executed
}

Example:

int count = 0;
while(count < 5){
    Console.WriteLine("Count: " + count);
    count++;
}
// Output: Count: 0, Count: 1, Count: 2, Count: 3, Count: 4

Explanation:

• Condition: The loop continues until count is no longer less than 5. If the condition evaluates to false before entering the loop, the loop body will not execute at all.

3. Do While Loop

Unlike while, the do while loop ensures that the loop body executes at least once because the condition is evaluated after the first iteration.

Syntax:

do{
    // Code to be executed
}while(condition);

Example:

int num = 0;
do{
    Console.WriteLine("Num: " + num);
    num++;
}while(num < 5);
// Output: Num: 0, Num: 1, Num: 2, Num: 3, Num: 4

Explanation:

• Execution: The loop runs at least once regardless of whether the condition num < 5 is true.
• Post Condition Check: After each iteration, the condition is checked to determine if the loop should continue.

4. Foreach Loop

The foreach loop iterates over elements in an array or collection without needing an index variable.

Syntax:

foreach(var item in collection){
    // Code to be executed
}

Example:

int[] numbers = {1, 2, 3, 4, 5};
foreach(int num in numbers){
    Console.WriteLine(num);
}
// Output: 1, 2, 3, 4, 5

Explanation:

• Iterate Through Collection: Simplifies looping through arrays or collections by automatically handling the iteration index.
• No Index Modification: Elements in the collection cannot be modified directly using this loop; doing so will result in a compilation error.

5. Break Statement

The break statement terminates the nearest enclosing for, while, do, switch, or foreach loop immediately.

Syntax:

loop {
    if(condition){
        break;
    }
    // Code to be executed
}

Example:

for(int i = 0; i < 10; i++){
    if(i == 5){
        break;
    }
    Console.WriteLine("i = " + i);
}
// Output: i = 0, i = 1, i = 2, i = 3, i = 4

Explanation:

• Exit Loop: When i equals 5, the break statement exits the loop.

6. Continue Statement

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

Syntax:

loop {
    if(condition){
        continue;
    }
    // Code to be executed
}

Example:

for(int i = 0; i < 5; i++){
    if(i == 3){
        continue;
    }
    Console.WriteLine("Number: " + i);
}
// Output: Number: 0, Number: 1, Number: 2, Number: 4

Explanation:

• Skip Iteration: When i equals 3, the continue statement is executed, skipping the remaining part of the loop's body.

7. Goto Statement

Although not specifically a loop control, the goto statement can be used to transfer control to any labeled statement, including exiting loops.

Syntax:

loop:
    // Code to be executed
    if(condition){
        goto end;
    }
end:
    // Code to be executed after exit

Example:

int j = 0;
start:
    if(j == 2){
        goto end;
    }
    Console.WriteLine("Value of j : " + j);
    j++;
    goto start;
end:
    Console.WriteLine("Exited loop");
// Output: Value of j : 0, Value of j : 1, Exited loop

Explanation:

• Unconditional Jump: The goto statement allows for jumping from one block of code to another.
• Caution: Overuse can lead to spaghetti code, making it difficult to maintain.

8. Return Statement

The return statement terminates the method and can be used inside loops to exit the method prematurely.

Syntax:

void MethodName(){
    loop {
        if(condition){
            return;
        }
        // Code to be executed
    }
}

Example:

void CheckNumber(int x){
    while(x < 10){
        if(x == 5){
            return;
        }
        Console.WriteLine("x = " + x);
        x++;
    }
    Console.WriteLine("Method finished");
}

CheckNumber(0);
// Output: x = 0, x = 1, x = 2, x = 3, x = 4

Explanation:

• Exit Method: When x equals 5, the return statement exits the CheckNumber method.

9. Try-Catch-Finally Block

These blocks handle exceptions within loops, ensuring code continues to run even if errors occur.

Syntax:

try {
    // Code that may throw exceptions
} catch (ExceptionType ex) {
    // Code that executes when an exception occurs
} finally {
    // Code that always executes
}

Example:

int[] values = {1, 2, 0, 4, 5};
foreach(int v in values){
    try {
        Console.WriteLine(10 / v);
    } catch (DivideByZeroException) {
        Console.WriteLine("Cannot divide by zero!");
    } finally {
        Console.WriteLine("Processing complete for value: " + v);
    }
}
// Output: 
// 10
// 5
// Cannot divide by zero!
// Processing complete for value: 0
// 2.5
// 2
// Processing complete for value: 5

Explanation:

• Exception Handling: The catch block handles division by zero for the third element in the array, while the finally block executes regardless.

10. Nested Loops

Loops within loops allow for complex iterations, such as generating tables or iterating over multidimensional arrays.

Syntax:

outerloop:
    // Code for outer loop
    innerloop:
        // Code for inner loop

Example:

for(int row = 1; row <= 3; row++){
    for(int col = 1; col <= 3; col++){
        Console.Write("* ");
    }
    Console.WriteLine();
}
// Output: 
// * * * 
// * * * 
// * * * 

Explanation:

• Outer Loop: Iterates rows.
• Inner Loop: Iterates columns, printing asterisks (*).
• Row Break: After completing each column iteration, a newline character is added.

Conclusion