添加新的XElement在保存時將整個XML文件追加到現有文件

Question

如果找不到一個新的xml文檔，然後將其打開以創建一個新條目，則會創建一個新的xml文檔。然而，它只是似乎是追加一個完整的新的XML文件來結束我的創建後創建

空白文件：

<?xml version="1.0" encoding="utf-8" standalone="yes"?> 
<Devices /> 

增加新的XElement後：

<?xml version="1.0" encoding="utf-8" standalone="yes"?> 
<Devices /><?xml version="1.0" encoding="utf-8" standalone="yes"?> 
<Devices> 
    <device> 
    <name>blah</name> 
    <src00>True</src00> 
    </device> 
</Devices> 

我的代碼.. 。我嘗試過添加兩種不同的方式，兩種方式都有相同的結果

  // Create file if not found 
      if (!storage.FileExists("settings\\mydevices.xml")) 
      { 
       using (IsolatedStorageFileStream stream = storage.OpenFile("settings\\mydevices.xml", FileMode.Create, FileAccess.ReadWrite)) 
       { 
        XDocument devicesDoc = 
         new XDocument(
          new XDeclaration("1.0", "utf-8", "yes"), 
          new XElement("Devices") 
          ); 

        System.IO.StreamWriter file = new System.IO.StreamWriter(stream); 
        devicesDoc.Save(file); 
        file.Dispose(); 
       } 
      } 


      // Add new device 
      using (IsolatedStorageFileStream stream = storage.OpenFile("settings\\mydevices.xml", FileMode.Open, FileAccess.ReadWrite)) 
      { 

       XDocument mydevicesXml = XDocument.Load(stream); 
       //XElement item= new XElement("device", 
       //    new XElement("name",selectedDeviceName), 
       //    new XElement("src00","True") 
       //    ); 

       //mydevicesXml.Descendants("Devices").First().Add(item); 
       //mydevicesXml.Element("Devices").Add(item); 

       mydevicesXml.Root.Add(
        new XElement("device", 
         new XElement("name", selectedDeviceName), 
         new XElement("src00", "True"))); 


       System.IO.StreamWriter file = new System.IO.StreamWriter(stream); 
       mydevicesXml.Save(file); 
       file.Dispose(); 

Answer 1

嘗試：

XElement root; 

if(File.Exists(file)) 
    root = XElement.Load(file); 
else 
    root = new XElement("Devices"); 

root.Add(new XElement("device", 
     new XElement("name", selectedDeviceName), 
     new XElement("src00", "True"))); 
root.Save(file);