使用LINQ反序列化XML时所有字段返回null问题求解

首先明确核心问题出在XML结构和读取逻辑不匹配，以及代码存在编写错误，具体解决方式如下： #

1. 核心问题：XML层级结构错误 #

你当前的XML所有站点属性、行李房属性都直接挂在根节点<RailwayStations>下，<RailwayStation />是完全没有子元素的空节点，所以你从<RailwayStation>节点下查询子元素自然全部返回null。
更合理的XML结构应该把每个站点的属性、对应行李房节点都包在<RailwayStation>内部，层级更清晰也符合通用序列化规范，修正后的XML示例：

<?xml version="1.0" encoding="utf-8"?>
<RailwayStations>
  <RailwayStation>
    <RailwayStationName>Verdansk</RailwayStationName>
    <RailwayStationCountOfWays>10</RailwayStationCountOfWays>
    <RailwayStationCountOfLuggageRooms>3</RailwayStationCountOfLuggageRooms>
    <LuggageRooms>
      <LuggageRoom>
        <RailwayStationLuggageRoomHeight>10</RailwayStationLuggageRoomHeight>
        <RailwayStationLuggageRoomWidth>20</RailwayStationLuggageRoomWidth>
        <RailwayStationLuggageRoomDepth>30</RailwayStationLuggageRoomDepth>
      </LuggageRoom>
      <LuggageRoom>
        <RailwayStationLuggageRoomHeight>11</RailwayStationLuggageRoomHeight>
        <RailwayStationLuggageRoomWidth>21</RailwayStationLuggageRoomWidth>
        <RailwayStationLuggageRoomDepth>31</RailwayStationLuggageRoomDepth>
      </LuggageRoom>
      <LuggageRoom>
        <RailwayStationLuggageRoomHeight>12</RailwayStationLuggageRoomHeight>
        <RailwayStationLuggageRoomWidth>22</RailwayStationLuggageRoomWidth>
        <RailwayStationLuggageRoomDepth>32</RailwayStationLuggageRoomDepth>
      </LuggageRoom>
    </LuggageRooms>
  </RailwayStation>
</RailwayStations>

2. 原有代码的额外错误 #

你的代码还存在两处明显编写问题：

• 读取行李房时仍然从根节点查询<RailwayStation>节点，本身该节点为空，自然读不到值
• 赋值行李房宽度、深度时，错误地都取了RailwayStationLuggageRoomHeight的值

3. 修正后的读取代码（适配上述修正后的XML结构） #

var xDoc = XDocument.Load(fileName);

var obj = from stationElem in xDoc.Root?.Elements("RailwayStation")
          select new RailwayStation()
          {
              RailwayStationName = stationElem.Element("RailwayStationName")?.Value,
              RailwayStationCountOfWays = Convert.ToInt32(stationElem.Element("RailwayStationCountOfWays")?.Value ?? "0"),
              RailwayStationCountOfLuggageRooms = Convert.ToInt32(stationElem.Element("RailwayStationCountOfLuggageRooms")?.Value ?? "0"),
              
              LuggageRooms = (from roomElem in stationElem.Element("LuggageRooms")?.Elements("LuggageRoom")
                              select new LuggageRoom()
                              {
                                  _luggageRoomHeight = Convert.ToInt32(roomElem.Element("RailwayStationLuggageRoomHeight")?.Value ?? "0"),
                                  _luggageRoomWidth = Convert.ToInt32(roomElem.Element("RailwayStationLuggageRoomWidth")?.Value ?? "0"),
                                  _luggageRoomDepth = Convert.ToInt32(roomElem.Element("RailwayStationLuggageRoomDepth")?.Value ?? "0"),
                              }).ToList()
          };
return obj;

4. 若你坚持不修改原有XML结构，可使用以下适配代码 #

如果不方便调整XML生成逻辑，也可以直接适配你当前的扁平XML结构：

var xDoc = XDocument.Load(fileName);
var root = xDoc.Root;
// 直接从根节点读取站点基础属性
var station = new RailwayStation()
{
    RailwayStationName = root.Element("RailwayStationName")?.Value,
    RailwayStationCountOfWays = Convert.ToInt32(root.Element("RailwayStationCountOfWays")?.Value ?? "0"),
    RailwayStationCountOfLuggageRooms = Convert.ToInt32(root.Element("RailwayStationCountOfLuggageRooms")?.Value ?? "0"),
    LuggageRooms = new List<LuggageRoom>()
};
// 按顺序匹配行李房的长宽高参数
var heights = root.Elements("RailwayStationLuggageRoomHeight").Select(e => e.Value).ToList();
var widths = root.Elements("RailwayStationLuggageRoomWidth").Select(e => e.Value).ToList();
var depths = root.Elements("RailwayStationLuggageRoomDepth").Select(e => e.Value).ToList();
for (int i = 0; i < heights.Count; i++)
{
    station.LuggageRooms.Add(new LuggageRoom()
    {
        _luggageRoomHeight = Convert.ToInt32(heights[i]),
        _luggageRoomWidth = Convert.ToInt32(widths[i]),
        _luggageRoomDepth = Convert.ToInt32(depths[i]),
    });
}
return new List<RailwayStation> { station };

内容的提问来源于stack exchange，提问作者LNxD