CS C#

C#: Control Flow

What you will learn

Conditionals, loops, and the foreach loop that C# uses to iterate collections.

if / else if / else

int score = 85;

if (score >= 90) {
    Console.WriteLine("A");
} else if (score >= 80) {
    Console.WriteLine("B");
} else {
    Console.WriteLine("F");
}

Loops

for loop

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

foreach loop (most common for collections)

string[] names = { "Alice", "Bob", "Charlie" };
foreach (string name in names) {
    Console.WriteLine(name);
}

while loop

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

Switch statement

string day = "Monday";
switch (day) {
    case "Monday":
        Console.WriteLine("Start of work week");
        break;
    case "Friday":
        Console.WriteLine("Almost weekend");
        break;
    default:
        Console.WriteLine("Midweek");
        break;
}

C# requires break at the end of each case (no fall-through unless you use goto case).

Common mistakes

  • Forgetting break in a switch case — compile error in C# (prevents the classic C++ fall-through bug)
  • Writing else if as one word (elseif) — it's two words in C#
  • Modifying a collection inside a foreach loop — use a for loop if you need to add/remove items

Quick check below!

Next: Methods & Classes