在c#中向列表中添加构造函数的类成员和数据成员

我有一个这样的类:

public class X
{
    public X()
    {
        Comments = new List<Y>();
    }
    [DataMember(Order = 0)]
    public string Key;
    [DataMember(Order = 1)]
    public List<Y> Comments;     
}
[DataContract]
public class Y
{
    [DataMember(Order = 0)]
    public string Body;
    [DataMember(Order = 1)]
    public string Author;
}

这是我如何添加到列表。

private List<X> Method(string result)
{
   List<X> ret = new List<X>
   List<X> temp = new List<X>
        { 
             new Y()
            {
                Body = Body,
                Author = Author
            },
            new X() {
            Key = issueKey,
            }  
        };
    ret.Add(temp);
    return ret;
  }

我做错了什么吗?我得到错误:添加集合初始化器有一些无效的参数，请建议如何解决这个问题?

private List<X> Method(string result)
    {
        List<X> ret = new List<X>();
        X temp = new X
        {
            Comments = new List<Y>
            {
                new Y() { Author = "Author", Body = "Body" }
            },
            Key = "issueKey"
        };
        ret.Add(temp);
        return ret;
    }