New Record types do not allow overriding the equals method

[tmccowan]

I started testing out record types in an application that I maintain and ran into some issues. The default == logic works just fine until you have a reference type property.

Here is an example of my problem

Person p1 = new() { FirstName = "Travis", LastName = "McCowan", Data = new byte[] { 1, 3, 5, 7, 9 } };
Person p2 = p1 with { Data = new byte[] { 1, 3, 5, 7, 9 } };

Console.WriteLine(p1 == p2); // False

public record Person
{
public string FirstName { get; init; }
public string LastName { get; init; }
public byte[] Data { get; init; }
}

Possible solutions to this issue

• Allow overriding of Equals or GetHashCode to determine equality.
• As record types compare the value of their properties by default, it could just evaluate the reference types the same way.

Person p1 = new() { FirstName = "Travis", LastName = "McCowan", Data = new byte[] { 1, 3, 5, 7, 9 } };
Person p2 = p1 with { Data = new byte[] { 1, 3, 5, 7, 9 } };

Console.WriteLine(p1 == p2); //True

public record Person
{
public string FirstName { get; init; }
public string LastName { get; init; }
public byte[] Data { get; init; }

public override int GetHashCode()
{
unchecked
{
const int HashingBase = (int)2166136261;
const int HashingMultiplier = 16777619;

int hash = HashingBase;
hash = (hash * HashingMultiplier) ^ FirstName.GetHashCode();
hash = (hash * HashingMultiplier) ^ LastName.GetHashCode();
hash = (hash * HashingMultiplier) ^ new BigInteger(Data).GetHashCode();
return hash;
}
}
}

[ufcpp]

public record Person
{
    public string FirstName { get; init; }
    public string LastName { get; init; }
    public byte[] Data { get; init; }

    // you can customize the equality by
    public virtual bool Equals(Person other)
    {
        return other != null
            && FirstName == other.FirstName
            && LastName == other.LastName
            && new BigInteger(Data) == new BigInteger(other.Data);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            const int HashingBase = (int)2166136261;
            const int HashingMultiplier = 16777619;

            int hash = HashingBase;
            hash = (hash * HashingMultiplier) ^ FirstName.GetHashCode();
            hash = (hash * HashingMultiplier) ^ LastName.GetHashCode();
            hash = (hash * HashingMultiplier) ^ new BigInteger(Data).GetHashCode();
            return hash;
        }
    }
}

[tmccowan]

@ufcpp Thank you for the sample. I'll use your suggestion in my project so I can move forward with record types.
It would still be nice for record types to work out of the box for all types.