C#如何添加一个特殊的xml节点

[mextb1860]

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
  </configSections>
  <connectionStrings>
    <add name="ConnectionString1" connectionString="Data Source=192.168.1.56;Initial Catalog=KSM000;User ID=sa;Password=bestcts"
      providerName="System.Data.SqlClient" />
    <add name="ConnectionString2" connectionString="Data Source=192.168.1.56;Initial Catalog=KSM000;User ID=sa;Password=bestcts"
      providerName="System.Data.SqlClient" />
  </connectionStrings>
  <dataConfiguration defaultDatabase="LocalhostString" />
</configuration>

我现在想在connectionStrings节点下添加一个 <add name="ConnectionString2" connectionString="Data Source=192.168.1.56;Initial Catalog=KSM000;User ID=sa;Password=bestcts"
providerName="System.Data.SqlClient" /> 这样的节点,老是添加不了.
因为这个xml节点的没有结尾符,只有个/> 我发现网络上的添加xml节点的都是有结尾符的.还有我想用xml的操作方式来操作web.config

[mextb1860]

都是这种

<title>Oberon's Legacy</title>
<author>Corets, Eva</author>
<price>5.95</price>

格式的.我要
<title name="Oberon's Legacy" />
这样子的

[mextb1860]

网上都是

    <title>Oberon's Legacy</title>
    <author>Corets, Eva</author>
    

种xml的节点.我要添加的节点需要是这样子的

<title nodeAtt="Oberon's Legacy" />
<author nodeAtt="Corets, Eva" />
<price nodeAtt="5.95" />

[XIEWH]

string path = Application.StartupPath + "\\LoginSet.xml";//路径
            XmlDocument xdoc = new XmlDocument();
            xdoc.Load(path);
            string nodename = "data/BB/UserName";//节点
            XmlNode node = xdoc.SelectSingleNode(nodename);
            XmlAttribute xa = xdoc.CreateAttribute("test");//属性
            xa.Value = "sdf";
            node.Attributes.Append(xa);
            XmlTextWriter xWriter = new XmlTextWriter(path, null);
            xWriter.Formatting = Formatting.Indented;
            xdoc.WriteTo(xWriter);
            xWriter.Close();

大概就是这样了

[mextb1860]

这个没有用.就是在找个节点,如何添加属性.
我要是生成节点,而且不是在找节点,如何在添加属性..
我需要生成这样的节点...
<title nodeAtt="Oberon's Legacy" />
<author nodeAtt="Corets, Eva" />
<price nodeAtt="5.95" />

[mextb1860]

属性我会添加,问题是 />这样子结尾.我不知道如何做,一般的节点都会有开始标记和结尾标记,而这种没有结尾的标记只用了一个
/>来结尾

[wzq6511]

private void addnewnode( string nodekey,string nodevalue)
		{
			try
			{
				System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
				xmlDoc.Load(sInstallPath+@"\web.config");
				System.Xml.XmlNode node;
				XmlNode fanode=xmlDoc.SelectSingleNode("//appSettings");
				node = xmlDoc.SelectSingleNode(string.Format("//appSettings/add[@key='{0}']",nodekey));
				if(node==null)
				{

					XmlElement connode=xmlDoc.CreateElement("add");
				
					//connode.Name="add";
					connode.SetAttribute("key",nodekey);
					connode.SetAttribute("value",nodevalue);
					//connode.Attributes["key"].Value=nodekey;
					//connode.Attributes["value"].Value=nodevalue;
				
					fanode.AppendChild(connode);
					xmlDoc.Save(sInstallPath+"web.config");

				}
			}
			catch(Exception er)
			{
				MessageBox.Show(er.ToString());
			}
		}