C# 向 Xdocument 添加新的 XElement
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Add new XElement to Xdocument
提问by anthonyhumphreys
I have the following code, which successfully writes to an XML file. However, it overwrites each time because of the tagRegistry.Save() call being made. How can I add a new XElement to the existing file? At the moment the file is simply overwritten.
我有以下代码，它成功写入 XML 文件。但是，由于进行了 tagRegistry.Save() 调用，它每次都会覆盖。如何向现有文件添加新的 XElement？目前该文件只是被覆盖。
public void saveTag()
{
if (File.Exists("/tagRegistry.xml"))
{
XElement tagRegistry = XElement.Load("/tagRegistry.xml");
XElement newTag = new XElement("Tag",
new XElement("tag", stringUid),
new XElement("name", desiredName),
new XElement("latitude", latitude),
new XElement("longitude", longitude));
tagRegistry.Add(newTag);
using (var storage = IsolatedStorageFile.GetUserStoreForApplication())
{
using (Stream stream = storage.CreateFile("/tagRegistry.xml"))
{
tagRegistry.Save(stream);
}
}
}
else
{
XDocument tagRegistry = new XDocument(new XElement("SmartSafe"));
tagRegistry.Element("SmartSafe").Add(new XElement("Tag",
new XElement("tag", stringUid),
new XElement("name", desiredName),
new XElement("latitude", latitude),
new XElement("longitude", longitude)));
using (var storage = IsolatedStorageFile.GetUserStoreForApplication())
{
using (Stream stream = storage.CreateFile("/tagRegistry.xml"))
{
tagRegistry.Save(stream);
}
}
}
}
采纳答案by Patrick Hallisey
Try this:
尝试这个：
public void saveTag()
{
using (var storage = IsolatedStorageFile.GetUserStoreForApplication())
{
XDocument document;
XElement tagRegistry = null;
if (storage.FileExists("/tagRegistry.xml"))
{
using(var stream = storage.OpenFile("/tagRegistry.xml", FileMode.Open))
{
document = XDocument.Load(stream);
}
tagRegistry = document.Descendants("SmartSafe").FirstOrDefault();
}
else
{
document = new XDocument();
}
if(tagRegistry == null)
{
tagRegistry = new XElement("SmartSafe");
document.Add(tagRegistry);
}
XElement newTag = new XElement("Tag",
new XElement("tag", stringUid),
new XElement("name", desiredName),
new XElement("latitude", latitude),
new XElement("longitude", longitude));
tagRegistry.Add(newTag);
using (Stream stream = storage.CreateFile("/tagRegistry.xml"))
{
document.Save(stream);
}
}
}
回答by CSJ
It's possible your File.Existscall is wrong. You are storing the file to isolated storage, but reading in from your current running directory. So you're always falling into the elseblock and writing a new file every time.
可能你的File.Exists电话打错了。您将文件存储到独立存储，但从当前运行的目录中读取。所以你总是陷入else困境并每次都写一个新文件。
