c# xml 的AppendChild问题 - .NET技术 / C#

C# code:

//代码如下：正常运行，就是添加到xml里后，显示没有 "</PlugInFile>"

try
{

string path = Application.StartupPath + (@"\PlugIn.xml");
XmlDocument doc = new XmlDocument();
doc.Load(path);

XmlNode node = doc.SelectSingleNode("PlugIn/PlugInConfig");
if (node == null)
return;
XmlElement ent = doc.CreateElement("PlugInFile");
ent.SetAttribute("text", 123);
ent.SetAttribute("ImpementInterface", 123);
ent.SetAttribute("ClassName", 123);

// XmlElement notexml = doc.CreateElement("Note");
// notexml.InnerText = this.txtnote.Text;
// node.AppendChild(notexml);
node.AppendChild(ent);
doc.Save(path);
MessageBox.Show("YES");
}
catch (Exception ex)
{ MessageBox.Show(ex.Message); }



xml数据：
XML code:

<?xml version="1.0" encoding="utf-8"?>
<PlugIn>
<Plug