无法将更改保存到xml文件

Question

As a learning exercise I'm building a simple Server IP storage and ping monitor application. The application reads a list of servers/hosts from the xml file and displays them to the user and allows them the ability to ping them to check their online status.

The read and ping functionality works fine but when writing code to add an additional server instance the code won't save the new element to the xml file.

Here's the basic XML structure in serverlist.xml :

<servers>
  <server name="Operations">
      <hostname>Operations</hostname>
      <hostaddress>address</hostaddress>
  </server>
  <server name="Development">
      <hostname>development</hostname>
      <hostaddress>address</hostaddress>
  </server>
</servers>

And here is the code I've used to add a new server element:

private void btnAdd_Click(object sender, EventArgs e)
        {
            XDocument xDocument = new XDocument();
            try
            {
                if (txtHostName.Text == "" || txtHostAddress.Text == "")
                {
                    MessageBox.Show("Please complete the fields shown!", "Complete form", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                }
                else
                {
                    // Add element to XML
                    if (File.Exists("serverlist.xml"))
                    {
                        xDocument = XDocument.Load("serverlist.xml");
                    }
                    else
                    {
                        MessageBox.Show("No XML available!", "Error", MessageBoxButtons.OK);
                    }

                    XElement newServer = new XElement("server", txtServerName.Text,
                            new XElement("hostname", txtHostName.Text),
                            new XElement("hostaddress", txtHostAddress.Text));

                    xDocument.Root.Add(newServer);


                    xDocument.Save("Serverlist.xml");
                    MessageBox.Show("Server Added!", "Server Added", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }

            }

I'm not seeing any errors or the catch clauses, the element is just not being saved to the XML. This is probably a very simple and silly thing, but I've done a lot of googling(other search engines are available!) and research into XML functions but I can't seem to see what I've missed.

Answer 1

Your XML saving code works fine if the "serverList.xml" file contains a valid XML document.

I have a few suggestions:

1. If the serverList.xml file does not exist, either return after the "No XML Available!" MessageBox OR create a new XDocument (see below)

2. Use the SetAttribute("name", txtServerName.Text) to create the name="Operations" attribute.

3. Make sure you are looking at the right "serverList.xml" file. "serverList.xml" needs to be in the same folder as the .exe that you are running. If you are debugging, then "serverList.xml" --> $(ProjectDir)\\bin\\Debug\\serverList.xml

    private void button1_Click(object sender, EventArgs e) { XDocument xDocument = new XDocument(); try { // Add element to XML if (File.Exists(@"C:\\Projects\\serverlist.xml")) { xDocument = XDocument.Load(@"C:\\Projects\\ServerList.xml"); } else { MessageBox.Show("No XML available!", "Error", MessageBoxButtons.OK); // create new document xDocument.Add(new XElement("servers")); } XElement newServer = new XElement("server", new XElement("hostname", txtHostName.Text), new XElement("hostaddress", txtHostAddress.Text)); newServer.SetAttributeValue("name", txtServerName.Text); xDocument.Root.Add(newServer); xDocument.Save(@"C:\\Projects\\Serverlist.xml"); MessageBox.Show("Server Added!", "Server Added", MessageBoxButtons.OK, MessageBoxIcon.Information); } catch (Exception exc) { MessageBox.Show(exc.ToString(), "Error"); } } 

Answer 2

The issue turned out to be the 'Copy to Output Directory' property for the serverlist.xml file. This meant that in building/rebuilding the solution during debugging the copy of the xml file was being overwritten with the fresh unmodified original xml file. So it didn't look like it had been saved at all, whereas it had but then been overwritten.