Question

Here is my problem:

I have this XML file:

<?xml version="1.0" encoding="utf-8" ?>
<settings>
  <app name="Application1">
    <log name="Log1" path="d:\paths\" filename="Log1File"/>
    <log name="Log2" path="d:\paths\"/>
    <log name="log3" path="d:\paths\" filename="Log3File"/>
  </app>
</settings>

And I’m trying to read it with LINQ and create object of this class:

  public class Apps
  {
    public string Name { get; set; }
    public IEnumerable<Logs> Logs { get; set; }
  }

  public class Logs
  {
    public string Name { get; set; }
    public string Path { get; set; }
    public string Filename { get; set; }
  }

So far I managed to create this bit of code however looks like it only gets first log element mean time I need all log elements for each app element:

   public static IEnumerable<Apps> GetAllApps()
    {
      var items = from a in db.Descendants("app")
                  orderby a.Attribute("name").Value
                  select new Apps
                  {
                    Name = a.Attribute("name").Value,
                    Logs = from b in a.Descendants("log")
                           select new Logs 
                           { 
                            Name = b.Attribute("name").Value,
                            Path = b.Attribute("path").Value,
                            Filename = b.Attribute("filename").Value
                           }
                  };

      return items;
    }

Answer 1

I used fluent API, but let you adapt as you prefer…

Problem is a NullReferenceException, as one of your Logs in xml has no “filename” attribute. And when you use “Value” on a null, you get a NRE.

So, check if the Attribute exists before trying to get it’s value.

var it = db.Descendants("app")
                    .OrderBy(app => app.Attribute("name").Value)
                    .Select(app => new Apps() {
                        Name = app.Attribute("name").Value,
                        Logs = app.Descendants("log").Select(a =>
                            new Logs() {
                                Name = a.Attribute("name") != null ? a.Attribute("name").Value : null,
                                Path = a.Attribute("path") != null ? a.Attribute("path").Value : null,
                                Filename = a.Attribute("filename") != null ? a.Attribute("filename").Value : null
                            }).ToList()
                    }).ToList();