✅ public readonly bool Equals(...)? - SOLVED

public struct PhoneNumberPrefix : IEqualityComparer<PhoneNumberPrefix>
{   
    public PhoneNumberPrefix(int intValue, string stringValue)
    {
        IntValue = intValue;
        StringValue = stringValue;
    }
    public int IntValue { get; set; } = 0;
    public string StringValue { get; set; } = "";

    public readonly bool Equals(PhoneNumberPrefix x, PhoneNumberPrefix y)
    {
        return x.IntValue == y.IntValue && x.StringValue == y.StringValue;
    }

    public  int GetHashCode(PhoneNumberPrefix obj)
    {
        throw new NotImplementedException();
    }
}