using System;

using System.Collections;

using System.Collections.Generic;

public class CardInfo : IEquatable<CardInfo>

{

    public int number;

    public int id;

​

    public CardInfo(int number, int id)

    {

        this.number = number;

        this.id = id;

    }

    public bool Equals(CardInfo other) => number == other.number && id == other.id;

}

​

public class Program

{

    public static void Main()

    {

        var arr = new List<CardInfo> { new(1, 2) };

        var idx = arr.IndexOf(new CardInfo(1,2));

        Console.WriteLine(idx);

    }

}