如果为空，c# XML到linq错误

本文关键字：linq 错误 XML 如果 | 更新日期: 2023-09-27 18:12:20

我有一个正在解析XML文件的method。

我的方法是: 
public static List<UpperLevelGPS> ParseXml(string Document) 
 {
            List<UpperLevelGPS> result = new List<UpperLevelGPS>();
            result.Clear();                                     
            doc = XDocument.Load(Document);
            result = (from n in doc.Descendants("level")
                      select new UpperLevelGPS()
                      {
                          CurrentLevel = int.Parse(n.Attribute("CurrentLevel").Value),
                          TeleNodes = (from l in n.Element("UpperLevelGPSs").Elements("UpperLevelGPS")
                                       select new TeleNodes()
                                       {
                                           id = (int)(l.Attribute("id")),
                                           UpperLevelGPSMapID = (int)l.Attribute("UpperLevelGPSMapID"),
                                           DestinationMapID = (int)l.Attribute("DestinationMapID"),
                                           HostelID = (int)l.Attribute("HostelID"),
                                           x = (float)l.Attribute("x"),
                                           y = (float)l.Attribute("y"),
                                           z = (float)l.Attribute("z")
                                       }).ToList()
                      }).ToList();
            return result;
}

节点UpperLevelGPSs并不总是存在于我的XML文件中，所以上面的query失败了。我如何捕获和处理null事件?

如果为空，c# XML到linq错误

检查linq语句前是否有:

public static List<UpperLevelGPS> ParseXml(string Document) 
    {
            List<UpperLevelGPS> result = new List<UpperLevelGPS>();
            result.Clear();                                     
            doc = XDocument.Load(Document);
            var upperLevelGPSs = n.Element("UpperLevelGPSs");
            if (upperLevelGPSs.Count > 0)
            {
                result = (from n in doc.Descendants("level")
                            select new UpperLevelGPS()
                            {
                                CurrentLevel = int.Parse(n.Attribute("CurrentLevel").Value),
                                TeleNodes = (from l in upperLevelGPSs .Elements("UpperLevelGPS")
                                            select new TeleNodes()
                                            {
                                                id = (int)(l.Attribute("id")),
                                                UpperLevelGPSMapID = (int)l.Attribute("UpperLevelGPSMapID"),
                                                DestinationMapID = (int)l.Attribute("DestinationMapID"),
                                                HostelID = (int)l.Attribute("HostelID"),
                                                x = (float)l.Attribute("x"),
                                                y = (float)l.Attribute("y"),
                                                z = (float)l.Attribute("z")
                                            }).ToList()
                            }).ToList();
            }
            return result;
}

注意:我还没有测试过。

                                   {
                                       id = (int)(l.Attribute("id")),
                                       UpperLevelGPSMapID = (int?)l.Attribute("UpperLevelGPSMapID"),
                                       DestinationMapID = (int)l.Attribute("DestinationMapID"),
                                       HostelID = (int)l.Attribute("HostelID"),
                                       x = (float)l.Attribute("x"),
                                       y = (float)l.Attribute("y"),
                                       z = (float)l.Attribute("z")
                                   }).ToList()
                  }).ToList();

(Int ?)

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