如何使用自定义对象的类型序列化列表列表？

Here is the code:

这是代码:

    [XmlRoot("Foo")]
    class Foo
    {
        [XmlElement("name")]
        string name;
    }

    [XmlRoot("FooContainer")]
    class FooContainer
    {
        [XmlElement("container")]
        List<List<Foo>> lst { get; set; }
    }

    XmlSerializer s = new XmlSerializer(typeof(FooContainer)); -->Can't pass through this.
    [XmlRoot("Foo")