C#高手进来看看啊

            int nsid = int.Parse(txtStation.Text);
            int dtid = int.Parse(txtDevicetype.Text);
            int did = int.Parse(txtDevice.Text);
            XmlDocument dom = new XmlDocument();
            dom.Load(Server.MapPath("XMLFile/Net.xml"));
            XmlNode xn = dom.SelectSingleNode("/root/netstation[@id=" + nsid + "]/devicetype[@id=" + dtid + "]/device[@id= " + did + "]/*");
            if ()
            {
                txtID.Text = xn.Attributes["id"].Value;
                txtValue.Text = xn.Attributes["value"].Value;
            }

判断netstation  devicetype device三个节点中的id在xml文件中是否存在  括号内应该填什么

try

{

 int nsid = int.Parse(txtStation.Text);
    int dtid = int.Parse(txtDevicetype.Text);
    int did = int.Parse(txtDevice.Text);
    XmlDocument dom = new XmlDocument();
    dom.Load(Server.MapPath("XMLFile/Net.xml"));
    XmlNode xn = dom.SelectSingleNode("/root/netstation[@id=" + nsid + "]/devicetype[@id=" + dtid + "]/device[@id= " + did + "]/*");
    txtID.Text = xn.Attributes["id"].Value;
    txtValue.Text = xn.Attributes["value"].Value;

}

catch{txtID.Text ="";txtValue.Text ="";}

如果是怕程序出错抛出异常，可以用try , cacth块截获这个异常。提示节点不存在。