如何在一个xml文件中添加一行?

Question

XmlDocument xmldoc = new XmlDocument();
xmldoc.Load("test.xml");XmlElement newnode = xmldoc.CreateElement("add");
newnode.SetAttribute("key","test");
newnode.SetAttribute("value","test");xmldoc.DocumentElement.AppendChild(newnode);XmlTextWriter xml = new XmlTextWriter("test.xml",null);
xml.Formatting = Formatting.Indented;
xmldoc.WriteContentTo(xml);

xml.Close();

Answer 1

XmlDocument XmlDoc=new XmlDocument();
XmlDoc.Load(@"E:\test.xml");XmlElement NewEle=XmlDoc.CreateElement("add");NewEle.SetAttribute("Key","Test");
NewEle.SetAttribute("Value","Test");
                
XmlDoc.DocumentElement.AppendChild((XmlNode) NewEle);XmlDoc.Save(@"E:\test.xml");

Answer 2

那如果xml文件是三层的,如下:
<Setting>
  <test>
    <add key="Name" value="SPS">
    </add>
    <add key="password" value="sag">
    </add>
    <add key="UserList" value="ProviderRoles">
    </add>
    <add key="FileList" value="55555">
    </add>
    <appSettings />
  </test>
</Setting>
我现在添加一行<add key="test" value="test"></add>
该怎么写代码?

Answer 3

XmlDoc.DocumentElement.AppendChild((XmlNode) NewEle);改为：XmlDoc.DocumentElement.FirstChild.AppendChild(NewEle);