无法使用线程和 XDocument 写入 XML 文件

Question

string filepath = Environment.CurrentDirectory + @"Expense.xml";

public void  WriteToXML(object param)
{
Expense exp = (Expense)param;
   if (File.Exists(filepath)) {
    XDocument xDocument = XDocument.Load(filepath);

    XElement root = xDocument.Element("Expenses");
    IEnumerable<XElement> rows = root.Descendants("Expense");
    XElement firstRow = rows.First();

    firstRow.AddBeforeSelf(new XElement("Expense",
           new XElement("Id", exp.Id.ToString()),
           new XElement("Amount", exp.Amount.ToString()),
           new XElement("Contact", exp.Contact),
           new XElement("Description", exp.Description),
           new XElement("Datetime", exp.Datetime)));
    xDocument.Save(filepath);
 }
}

Expense exp = new Expense();
exp.Id = new Random().Next(1, 10000);
exp.Amount = float.Parse(text1[count].Text);
exp.Contact = combo1[count].SelectedItem.ToString();
exp.Description = rtext1[count].Text.ToString();
exp.Datetime = DateTime.Now.ToString("MM-dd-yyyy");

workerThread = new Thread(newParameterizedThreadStart(WriteToXML));
workerThread.Start(exp); // throws System.IO.IOException

我无法使用 worker treads 写入 XML 文件 - 我收到此错误：

System.IO.IOException: 'The process cannot access the file 'C:\work\FinanceManagement\FinanceManagement\bin\DebugExpense.xml' because it is being used by another process.

但如果我像 WriteToXML(exp); 那样使用它，它就会起作用。我认为 XDocument.Load(filepath) 不是线程安全的。我该如何解决这个问题？

Answer 1

尝试引入一个 lock，看看它是否能解决问题：

// Declare this somewhere in your project, can be in same class as WriteToXML
static object XmlLocker;

然后用lock包裹逻辑：

public void WriteToXML(object param)
{
    Expense exp = (Expense)param;

    lock (XmlLocker) // <-- this limits one thread at a time
    {
        if (File.Exists(filepath))
        {
            XDocument xDocument = XDocument.Load(filepath);

            XElement root = xDocument.Element("Expenses");
            IEnumerable<XElement> rows = root.Descendants("Expense");
            XElement firstRow = rows.First();

            firstRow.AddBeforeSelf(new XElement("Expense",
                   new XElement("Id", exp.Id.ToString()),
                   new XElement("Amount", exp.Amount.ToString()),
                   new XElement("Contact", exp.Contact),
                   new XElement("Description", exp.Description),
                   new XElement("Datetime", exp.Datetime)));
            xDocument.Save(filepath);
        }
    }
}

无法使用线程和 XDocument 写入 XML 文件

Unable to write to XML file using threads and XDocument

c#

xml

linq-to-xml

worker-thread