Loops in C#

C# gives you four ways to repeat code, and each communicates a slightly different intent to whoever reads it later.

for: when you know the count

for (int i = 0; i < 5; i++)
{
    Console.WriteLine(i);
}

The three parts — initializer, condition, increment — run in that order every iteration. Use for when the loop is fundamentally about a counter or index.

while and do-while: when you don't know the count upfront

int attempts = 0;
while (attempts < 3)
{
    Console.WriteLine("Attempt " + attempts);
    attempts++;
}

while checks the condition before each iteration, so it might not run at all. do-while checks after, guaranteeing at least one run:

string? input;
do
{
    Console.Write("Enter 'quit' to exit: ");
    input = Console.ReadLine();
} while (input != "quit");

That's the right shape whenever "run once, then keep going while a condition holds" describes what you actually want — a menu prompt being the classic example.

foreach: when you're iterating a collection

var names = new List<string> { "Ada", "Grace", "Alan" };
foreach (var name in names)
{
    Console.WriteLine(name);
}

foreach is the most common loop in real C# code. It works over anything implementing IEnumerable<T> (arrays, lists, dictionaries, and — as you'll see in the LINQ lessons — query results), and it reads directly as "for each item in this collection," with no index bookkeeping to get wrong.

break and continue

Both work the same as in most C-family languages:

foreach (var name in names)
{
    if (name == "Grace") continue; // skip this iteration
    if (name == "Alan") break;      // stop the loop entirely
    Console.WriteLine(name);
}

Choosing the right one

Default to foreach whenever you're processing a collection and don't need the index. Reach for for when you genuinely need the index (or need to loop over a range without a backing collection), and while/do-while when the stopping condition isn't "run N times" but "keep going until something happens." Picking the loop that matches your actual intent makes the code more honest about what it's doing, even before anyone reads the body.