Records and Modern Types

Value Equality

Records compare their stored values, not just object identity.

value equality Value equality means two objects are equal when their data is equal.

Value Equality

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

record Point(int X, int Y)
{
    public override string ToString()
    {
        return X + "," + Y;
    }
}

class Program
{
    static void Main()
    {
        int x = 3;
        Point first = new Point(x, 4);
        Point second = new Point(x, 4);
        bool equal = first == second;

        Console.WriteLine($"x={x}");
        Console.WriteLine($"equal={equal}");
    }
}

using System;

record Point(int X, int Y)
{
    public override string ToString()
    {
        return X + "," + Y;
    }
}

class Program
{
    static void Main()
    {
        int x = 2;
        Point first = new Point(x, 4);
        Point second = new Point(x, 4);
        bool equal = first == second;

        Console.WriteLine($"x={x}");
        Console.WriteLine($"equal={equal}");
    }
}

using System;

record Point(int X, int Y)
{
    public override string ToString()
    {
        return X + "," + Y;
    }
}

class Program
{
    static void Main()
    {
        int x = 5;
        Point first = new Point(x, 4);
        Point second = new Point(x, 4);
        bool equal = first == second;

        Console.WriteLine($"x={x}");
        Console.WriteLine($"equal={equal}");
    }
}

  1. x ← 3, first ← 3,4, second ← 3,4, equal ← True

    12{13    static void Main()14    {15        int x→ 3 = 3; //@x=2, 516        Point first→ 3,4 = new Point(x, 4);17        Point second→ 3,4 = new Point(x, 4);18        bool equal→ True = first3,4 == second3,4;1920        Console.WriteLine($"x={x3}");21        Console.WriteLine($"equal={equalTrue}");22    }
    outputx=3
equal=True

  1. x ← 2, first ← 2,4, second ← 2,4, equal ← True

    12{13    static void Main()14    {15        int x→ 2 = 2;16        Point first→ 2,4 = new Point(x, 4);17        Point second→ 2,4 = new Point(x, 4);18        bool equal→ True = first2,4 == second2,4;1920        Console.WriteLine($"x={x2}");21        Console.WriteLine($"equal={equalTrue}");22    }
    outputx=2
equal=True

  1. x ← 5, first ← 5,4, second ← 5,4, equal ← True

    12{13    static void Main()14    {15        int x→ 5 = 5;16        Point first→ 5,4 = new Point(x, 4);17        Point second→ 5,4 = new Point(x, 4);18        bool equal→ True = first5,4 == second5,4;1920        Console.WriteLine($"x={x5}");21        Console.WriteLine($"equal={equalTrue}");22    }
    outputx=5
equal=True