Express Yourself! Motivating Example

Declarative.cs

public int WhatDoIDo(int[] numbers)
{
    return numbers.Count(i => i % 2 == 0)
}

Imperative.cs

public int WhatDoIDo(int[] numbers)
{
    var count = 0;

    foreach (var i in numbers)
    { 
        if (i % 2 == 0)
        {
            count++;
        }
    }

    return count;
}

Readable_Declarative.cs

public class public int WhatDoIDo(int[] numbers)
{
    return numbers.Count(IsEven)
}

private static bool IsEven(int i)
{
    return i % 2 == 0;
}

Readable_Declarative_Language_Features.cs

public int WhatDoIDo(int[] numbers)
{
    return numbers.Count(i => i.IsEven());
}

public static class MathExtensions
{
    public static bool IsEven(this int i)
    {
        return i % 2 == 0;
    }
}