自定义属性的关系

Question

这是我的数据库代码：

public class User {
    public int Id {get; set;}

    public ICollection<Vote> Votes {get; set;}

    public User() {
        Votes = new List<Vote>();
    }
}

public class Video {
    public int Id {get; set;}
    public int OnsiteId {get; set;}

    public ICollection<Vote> Votes {get; set;}

    public Video() {
        Votes = new List<Vote>();
    }
}

public class Vote {
    public int Id {get; set;}

    public int UserId { get; set; }
    [ForeignKey("UserId")]
    public User User { get; set; }

    public int VideoOnsiteId { get; set; }
    [ForeignKey("VideoOnsiteId")]
    public Video Video { get; set; }    
}

出于某种原因，Votes表包含VideoOnsiteId列，而Video.Id代替Video.OnsiteId。结果是我无法向数据库添加一行，因为我对FOREIGN KEY约束感到困惑。我怎么能改变它？