Foreach Loop

After this lesson you can

• Visit every element of an array with a foreach loop
• Stop a loop early with break, or skip to the next iteration with continue

Key takeaways

• foreach (string name in names) hands you each element in order, with no index to get wrong.
• foreach only reads, forward. Use for when you need the index, want to change elements, or go backward or in steps.
• To find the highest value, start with the first element, not 0, and replace it whenever you find a bigger one.
• break ends a loop at once; continue skips the rest of this iteration and goes on to the next.

Most of the time you loop through an array, you want every element, in order, and the index is just a way to get there. A foreach loop skips the index and hands you each element directly.

The shape

string[] names = { "Alice", "Bob", "Charlie" };

// read it as: for each name in names
foreach (string name in names)
{
    Console.WriteLine(name);
}

Alice
Bob
Charlie

Each iteration, name holds the next element. There's no counter to start, check or step, so there's no way to get the bounds wrong.

You can write var instead of the type, and C# works it out from the array: foreach (var name in names).

Adding up with foreach

The total pattern from the for loop lesson is shorter with foreach:

decimal[] prices = { 12.75m, 10.25m, 8.44m, 9.20m };
decimal total = 0;

foreach (decimal price in prices)
{
    total += price;
}

Console.WriteLine("Total: quot; + total);

Total: $40.64

Finding the highest

Another everyday pattern: keep the best value so far, and replace it whenever you find a better one.

decimal[] prices = { 12.75m, 10.25m, 21.34m, 9.20m };
decimal highest = prices[0];

foreach (decimal price in prices)
{
    if (price > highest)
    {
        highest = price;
    }
}

Console.WriteLine("Highest price: quot; + highest);

Highest price: $21.34

Start with the first element, not 0: if every price were negative, 0 would be wrong.

What foreach can't do

foreach only reads, forward, one element at a time. When you need any of these, use a for loop:

• the index itself (to print 1., 2., 3., or to compare neighbors);
• to change the array's elements (name is a copy; assigning to it is an error);
• to go backward, or skip elements.

Leaving early: break and continue

Two keywords change how any loop runs:

• break ends the loop at once. The program carries on after it.
• continue skips the rest of this iteration and goes on to the next.

string[] names = { "Ron", "Lisa", "Kent", "Michelle" };
bool found = false;

foreach (string name in names)
{
    if (name == "Kent")
    {
        found = true;
        break;
    }
}

Console.WriteLine("Found Kent: " + found);

int[] numbers = { 1, 2, 3, 4, 5, 6 };
int evenTotal = 0;

foreach (int number in numbers)
{
    if (number % 2 != 0)
    {
        continue;
    }
    evenTotal += number;
}

Console.WriteLine("Total of the even numbers: " + evenTotal);

Found Kent: True
Total of the even numbers: 12

Once Kent is found there's no need to look further, so break stops the search. continue skips each odd number before it's added.

for or foreach?

Check yourself

2 questions to try on the lesson page.

So what

foreach says what you mean, "every element", with nothing to get wrong. Reach for for when the index matters, and use break and continue to stop or skip without extra conditions.

Key terms

• foreach Loop
• break
• continue

Cheat sheets

• Foreach Loop