XDocument 写入重复的 xml

问题描述

我有一种方法可以将 XML 加载到 XDocument 并修改其元素然后保存.但是当我重新加载它时.我收到此错误:

I have a method which load XML to a XDocument and modify its elements then save.But when I reload it. I got this error :

意外的 XML 声明.XML 声明必须是文档中的第一个节点，并且不允许在它之前出现空格字符.

我检查了 XML，发现 XDocument 没有保存更改的内容，而是创建了一个副本并保存.

I checking the XML and see that the XDocument didn't save the changed but create a duplicate and save.

它像这个示例xml一样保存旧的和新的:

It save the old one and the new one like this example xml :

<?xml version="1.0" encoding="UTF-8"?>
<Ungdungs>
  <Ungdung>
    <Name>HERE City Lens</Name>
    <Id>b0a0ac22-cf9e-45ba-8120-815450e2fd71</Id>
    <Path>/Icon/herecitylens.png</Path>
    <Version>Unknown</Version>
    <Category>HERE</Category>
    <Date>Uknown</Date>
  </Ungdung>
<?xml version="1.0" encoding="UTF-8"?>
<Ungdungs>
  <Ungdung>
    <Name>HERE City Lens</Name>
    <Id>b0a0ac22-cf9e-45ba-8120-815450e2fd71</Id>
    <Path>/Icon/herecitylens.png</Path>
    <Version>1.0.0.0</Version>
    <Category>HERE</Category>
    <Date>Uknown</Date>
  </Ungdung>

这里是我用来修改和保存 XML 的代码:

Here the code I used to modify and save XML :

using (Stream stream = storage.OpenFile("APPSDATA.xml", FileMode.Open, FileAccess.ReadWrite))
                {
                    //var xdoc = XDocument.Load("APPSDATA.xml");
                    var xdoc = XDocument.Load(stream, LoadOptions.None);
                    var listapp = from c in xdoc.Descendants("Ungdung") select c;

                    foreach (XElement app in listapp)
                    {
                        var xElement = app.Element("Name");
                        if (xElement != null)
                            progressIndicator.Text = "Checking " + xElement.Value + "...";
                        var element = app.Element("Id");
                        if (element != null)
                        {
                            var appId = element.Value;
                            var appVersion = await GetAppsVersion(appId);
                            app.Element("Version").Value = appVersion.ToString();
                        }
                    }

                    xdoc.Save(stream);
                }

我该如何解决这个问题?

How can I solve this problem ?

推荐答案

看起来您正在将修改后的文档附加到当前文件内容的末尾.这就是为什么你以后不能再次解析它.

Looks like you're appending modified document at the end of current file content. That's why you can't parse it later again.

我会将 read 和 write 部分分成不同的 using 语句:

I would split read and write parts into different using statements:

XDocument xdoc;

using (Stream stream = storage.OpenFile("APPSDATA.xml", FileMode.Open, FileAccess.Read))
{
    xdoc = XDocument.Load(stream, LoadOptions.None);
}

var listapp = from c in xdoc.Descendants("Ungdung") select c;

foreach (XElement app in listapp)
{
    var xElement = app.Element("Name");
    if (xElement != null)
        progressIndicator.Text = "Checking " + xElement.Value + "...";
    var element = app.Element("Id");
    if (element != null)
    {
        var appId = element.Value;
        var appVersion = await GetAppsVersion(appId);
        app.Element("Version").Value = appVersion.ToString();
    }
}

using (Stream stream = storage.OpenFile("APPSDATA.xml", FileMode.Truncate, FileAccess.Write))
{
    xdoc.Save(stream);
}

在第二个 using 语句上设置 FileMode.Truncate 将清除以前的文件内容，应该如何解决您的问题.

Setting FileMode.Truncate on second using statement will clear previous file content, what should fix your problem.

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