C# by Example: Foreach


using System;
using System.Collections.Generic;
class Foo
{
    Dictionary<string, string> _someDictionary = new Dictionary<string, string>();
    
    void Main()
    {
        int[] numbers = [1,2,3,7,4,18,43,193]

A foreach loop is a convenient way to iterate over a list. It's generally preferred over for loops, as they are easier to read. That said, they are less flexible than for loops.


        foreach(int number in numbers)
        {
            Console.WriteLine($"Here is a number: {number}");
        }

You can use the keyword 'var' to let C# infer the type.


        foreach (var kvp in _someDictionary)
        {
            Console.WriteLine($"Key: {kvp.Key}, Val: {kvp.Value}");
        }
    }


    public class Color(float r, float g, float b)
    {
        public float r = r,g = g,b = b;
    }
    
    void ImmutableIterator()
    {
        List<Color> _colors = [new Color(0, 0, 0), new Color(1, 1, 1)];
        foreach (var color in _colors)
        {

This won't work! Error! You can't directly modify iterator values. Use a for loop instead.


            color = new Color(.8f, .1f, .4f);

This will work, because this color iterator variable (that we aren't allowed to assign to) is reference, and we aren't actually changing the color variable. We are following the reference, and then modifying one of it's members.


            color.r = 0;
        }
    
    }
}

Further:

Loops

Next example: Expression-Bodied Properties.