Collections

Foreach Sum

A foreach loop can aggregate values from a collection.

aggregate An aggregate calculation combines several values into one result.

Foreach Sum

bonus
ForeachSum.cs
Replay: real traced execution (multi-file project)
using System;

class Program
{
    static void Main()
    {
        int bonus = 1;
        int[] values = { 2, 4, 6 };
        int total = 0;

        foreach (int value in values)
        {
            total += value + bonus;
        }

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"total={total}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int bonus = 0;
        int[] values = { 2, 4, 6 };
        int total = 0;

        foreach (int value in values)
        {
            total += value + bonus;
        }

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"total={total}");
    }
}

using System;

class Program
{
    static void Main()
    {
        int bonus = 3;
        int[] values = { 2, 4, 6 };
        int total = 0;

        foreach (int value in values)
        {
            total += value + bonus;
        }

        Console.WriteLine($"bonus={bonus}");
        Console.WriteLine($"total={total}");
    }
}

  1. bonus ← 1, total ← 0

    4{5    static void Main()6    {7        int bonus→ 1 = 1; //@bonus=0, 38        int[] values = { 2, 4, 6 };9        int total→ 0 = 0;

  2. total ← 3

    pass 1 of 3
    11foreach (int value2 in values)12{13    total→ 3 += value2 + bonus1;14}
    All 3 passes — pass 1 is the card above
    passvaluetotal
    123
    248
    3615

  3. Console.WriteLine($"bonus={bonus}");

    16    Console.WriteLine($"bonus={bonus1}");17    Console.WriteLine($"total={total15}");18}
    outputbonus=1
total=15

  1. bonus ← 0, total ← 0

    4{5    static void Main()6    {7        int bonus→ 0 = 0;8        int[] values = { 2, 4, 6 };9        int total→ 0 = 0;

  2. total ← 2

    pass 1 of 3
    11foreach (int value2 in values)12{13    total→ 2 += value2 + bonus0;14}
    All 3 passes — pass 1 is the card above
    passvaluetotal
    122
    246
    3612

  3. Console.WriteLine($"bonus={bonus}");

    16    Console.WriteLine($"bonus={bonus0}");17    Console.WriteLine($"total={total12}");18}
    outputbonus=0
total=12

  1. bonus ← 3, total ← 0

    4{5    static void Main()6    {7        int bonus→ 3 = 3;8        int[] values = { 2, 4, 6 };9        int total→ 0 = 0;

  2. total ← 5

    pass 1 of 3
    11foreach (int value2 in values)12{13    total→ 5 += value2 + bonus3;14}
    All 3 passes — pass 1 is the card above
    passvaluetotal
    125
    2412
    3621

  3. Console.WriteLine($"bonus={bonus}");

    16    Console.WriteLine($"bonus={bonus3}");17    Console.WriteLine($"total={total21}");18}
    outputbonus=3
total=21

Add Each Value

  1. Start total at 0.
  2. Visit each value in { 2, 4, 6 }.
  3. Add the value plus bonus.
  4. Print the final total after the loop ends. | Value | Added when bonus is 1 | Running total | | --- | --- | --- | | 2 | 3 | 3 | | 4 | 5 | 8 | | 6 | 7 | 15 |

Exercise: ForeachSum.cs

Use foreach to add each value plus a bonus and print the final total