A for loop is a control structure that repeats a block of code a specific number of times. It is one of the most used control structures in C#.
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Basic Syntax
The syntax of a for loop in C# consists of three main parts: initialization, condition, and update. These parts are specified within the parentheses of the for loop and are separated by semicolons.
The basic structure of a for loop in C# is as follows:
for (initialization; condition; update)
{
// Instructions to execute in each iteration
}
Let’s look at each of the parts:
Initialization:In this part of the loop, the initial values of the variables that will control the loop’s execution are set (usually used to initialize a counter that will be incremented or decremented in each iteration)Condition:The condition is a boolean expression evaluated before each iteration. If the condition is true, the instructions inside the loop are executed. If the condition is false, the loop is exited and program execution continuesUpdate:In this part of the loop, an action is performed that modifies the value of the variables controlling the loop (usually used to increment or decrement the counter)Instructions to execute:Here, the instructions executed in each iteration are specified. These instructions can be any valid C# code (such as assignments, calculations, method calls, etc.)
Basic Example
Let’s see a simple example where a for loop is used to print numbers from 1 to 10:
for (int i = 1; i <= 10; i++)
{
Console.WriteLine(i);
}
In this example:
- The initialization
int i = 1sets the initial value ofito 1. - The condition
i <= 10ensures the loop executes whileiis less than or equal to 10. - The update
i++incrementsiby 1 after each iteration. - Inside the loop, we use the
Console.WriteLine()method to print the current value ofito the console.
The result is that numbers from 1 to 10 will be displayed on the screen.
Modifying Loop Flow
Skipping Iterations with continue
The continue statement is used to skip the current iteration and move directly to the next iteration of the loop.
for (int i = 0; i < 10; i++)
{
if (i % 2 == 0)
{
continue; // Skip even numbers
}
Console.WriteLine(i);
}
Breaking the Loop with break
Using the break statement allows exiting the loop before the condition is met. This is useful in situations where a specific value is found and there’s no need to continue iterating.
for (int i = 0; i < 10; i++)
{
if (i == 5)
{
break;
}
Console.WriteLine(i);
}
Special Cases
It is possible to create more “original” cases of the For loop. In general, it’s not a good idea to do so. But I’m telling you, if only so that if you ever see it, you can scold someone. 😉
Using External Variables
It is possible to use a variable declared outside the for loop as the control variable. However, this can lead to confusion and errors if not managed properly:
int i = 0;
for (i = 0; i < 5; i++)
{
Console.WriteLine(i);
}
Console.WriteLine($"Value of i after the loop: {i}");
In this case, i retains its value after the loop has finished, which will be 5.
Multiple Declarations
In the initialization and update sections, you can include multiple statements separated by commas. This is useful when you need several control variables:
for (int i = 0, j = 10; i < j; i++, j--)
{
Console.WriteLine($"i: {i}, j: {j}");
}
Practical Examples
Generate a Multiplication Table
In this example, a multiplication table for a specific number is generated using a for loop.
int number = 5; // Number for which the multiplication table is generated
for (int i = 1; i <= 10; i++) // Iterates from 1 to 10
{
Console.WriteLine($"{number} x {i} = {number * i}"); // Prints the multiplication of the number by 'i'
}
Iterating Over Arrays
One of the most common applications of the for loop is iterating over the elements of an array. Here is an example that sums all elements of an array:
int[] numbers = { 1, 2, 3, 4, 5 }; // Declare the array
int sum = 0; // Variable to store the sum
for (int i = 0; i < numbers.Length; i++)
{
sum += numbers[i]; // Add each element of the array to 'sum'
}
Console.WriteLine($"The sum of the elements is: {sum}");
Iteration with Different Step
The update value doesn’t always have to be an increment of one. It can be any expression that modifies the control variable. For example, iterating in steps of two:
for (int i = 0; i < 10; i += 2) // Increments 'i' by 2 in each iteration
{
Console.WriteLine(i); // Prints the current value of 'i'
}
Decrementing For Loop
The for loop can also be used to iterate in descending order:
for (int i = 10; i > 0; i--) // Decrements 'i' by 1 in each iteration
{
Console.WriteLine(i); // Prints the current value of 'i'
}
Searching for an Element in an Array
int[] numbers = { 1, 2, 3, 4, 5 }; // Declare the array
int search = 3; // Number to search for
bool found = false; // Variable to indicate if the number was found
for (int i = 0; i < numbers.Length; i++)
{
if (numbers[i] == search) // Compares each element with the searched number
{
found = true; // Marks that the number was found
break; // Exits the loop
}
}
if (found)
{
Console.WriteLine($"The number {search} is found in the array.");
}
else
{
Console.WriteLine($"The number {search} is not found in the array.");
}
These examples are intended to show how to use the For loop. It does not mean it’s the best way to solve the problem they address. Usually, there are better alternatives.
