using System;

​

public class Player

{

    public int kills = 0;

}

​

public abstract class Condition

{

    public float amount = 0;

    public abstract bool Test(Player player);

}

​

public class Mission

{

    public Condition[] conditions;

}

​

public class Kills : Condition

{   

    public Kills(int kills)

    {

        amount = kills;

    }

    public override bool Test(Player player)

    {

        return player.kills > amount;

    }

}

​

public NpcAlive : Condition

{

    public override bool Test(NPC npc)

    {

        return npc.isAlive;

    }

}

​

public class Program

{   

    public static void Main()

    {

        var mission = new Mission();

        mission.conditions = new Condition[]{ new Kills(5), NpcAlive(someNpc) };

    }

}