Question

我有以下代码，它成功写入XML文件。但是，由于正在进行tagRegistry.Save（）调用，它每次都会覆盖。如何在现有文件中添加新的XElement？目前文件只是被覆盖。

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);
            }
        }
    }
}

Answer 1

试试这个：

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);
        }
    }
}

Answer 2

您的File.Exists电话可能是错误的。您将文件存储到独立存储，但从当前运行目录读入。所以你总是落入else块并且每次都写一个新文件。

将新XElement添加到Xdocument

2 个答案: