如何通过属性选择XML节点并使用其子节点数据？

Question

Here is my XML file

<?xml version="1.0" encoding="utf-8" ?> 
<storage>   
<Save Name ="Lifeline">
 <Seconds>12</Seconds>
 <Minutes>24</Minutes>
 <Hours>9</Hours>
 <Days>25</Days>
 <Months>8</Months>
 <Years>2010</Years>
 <Health>90</Health>
 <Mood>100</Mood>  
</Save> 

<Save Name ="Hellcode">   
 <Seconds>24</Seconds>
 <Minutes>48</Minutes> 
 <Hours>18</Hours>
 <Days>15</Days>
 <Months>4</Months>
 <Years>1995</Years>
 <Health>50</Health>
 <Mood>50</Mood>  
</Save> 

Here is a code which get's data from XML and loads it into application.

System.IO.StreamReader sr = new System.IO.StreamReader(@"Saves.xml");

System.Xml.XmlTextReader xr = new System.Xml.XmlTextReader(sr);

System.Xml.XmlDocument save = new System.Xml.XmlDocument();

save.Load(xr);


XmlNodeList saveItems = save.SelectNodes("Storage/Save");

XmlNode seconds = saveItems.Item(0).SelectSingleNode("Seconds");
sec = Int32.Parse(seconds.InnerText);

XmlNode minutes = saveItems.Item(0).SelectSingleNode("Minutes");
min = Int32.Parse(minutes.InnerText);

XmlNode hours = saveItems.Item(0).SelectSingleNode("Hours");
hour = Int32.Parse(hours.InnerText);

XmlNode days = saveItems.Item(0).SelectSingleNode("Days");
day = Int32.Parse(days.InnerText);

XmlNode months = saveItems.Item(0).SelectSingleNode("Months");
month = Int32.Parse(months.InnerText);

XmlNode years = saveItems.Item(0).SelectSingleNode("Years");
year = Int32.Parse(years.InnerText);

XmlNode health_ = saveItems.Item(0).SelectSingleNode("Health");
health = Int32.Parse(health_.InnerText);

XmlNode mood_ = saveItems.Item(0).SelectSingleNode("Mood");
mood = Int32.Parse(mood_.InnerText);

The problem is that this code loads data inly from "Lifeline" node. I would like to use a listbox and be able to choose from which node to load data.

I've tried to take string from listbox item content and then use such a line

XmlNodeList saveItems = save.SelectNodes(string.Format("storage/Save[@Name = '{0}']", name)); 

variable "name" is a string from listboxe's item. While compiled this code gives exception. Do somebody knows a way how to select by attribute and load nedeed data from that XML?

Answer 1

If you can use XElement:

XElement xml = XElement.Load(file);
XElement storage = xml.Element("storage");
XElement save = storage.Elements("Save").FirstOrDefault(e => ((string)e.Attribute("Name")) == nameWeWant);
if(null != save) 
{
// do something with it
}

Personally I like classes that have properties that convert to and from the XElement to hide that detail from the main program. IE say the Save class takes an XElement node in the constructor, saves it internally globally, and the properties read/write to it.

Example class:

  public class MyClass
    {
      XElement self;
      public MyClass(XElement self)
      {
         this.self = self;
      }

    public string Name
    {
      get { return (string)(self.Attribute("Name") ?? "some default value/null"); }
      set 
      { 
        XAttribute x = source.Attribute("Name");
        if(null == x)
          source.Add(new XAttribute("Name", value));
        else
          x.ReplaceWith(new XAttribute("Name", value));
      }
    }
   }

Then you can change the search to something like:

XElement save = storage.Elements("Save")
    .FirstOrDefault(e => new MyClass(e).Name == NameWeWant);

Answer 2

The select nodes is returning two XmlNode objects.

XmlNodeList saveItems = save.SelectNodes("Storage/Save");

Later in your code you seem to be selecting the first one and with saveItems.Item(0) and getting values from it which in this case would be the save node with the Name="LifeLine". So if you were to do saveItems.Item(1) and select nodes and its values then you would get the other set of nodes.

Answer 3

Since it is not that much data, I'd suggest loading all information to a list of saves(constructor) and then drawing from there which one the user would like to use...

As for things not working, I personally use a lower level approach to get my data and it is not error prone. Remodeling it to fit your problem a bit:

int saves = 0;

List<Saves> saveGames = new List<Saves>();

saveGames.Add(new Saves());

while (textReader.Read())
{
   if (textReader.NodeType == XmlNodeType.Element)
      whatsNext = textReader.Name;
   else if (textReader.NodeType == XmlNodeType.Text)
   {
      if (whatsNext == "name")
         saveGames[saves].name = Convert.ToString(textReader.Value);
      //else if statements for the rest of your attributes
      else if (whatsNext == "Save")
      {
         saveGames.Add(new Saves());
         saves++;
      }
   }
   else if (textReader.NodeType == XmlNodeType.EndElement)
      whatsNext = "";
}

Basically throw everything in the xml file into a list of objects and manipulate that list to fill the listbox. Instead of having Saves name = "...", have a name attribute as the first attribute in the save.

Code tags hate me. Why they break so easily ( ._.)