How do I add xml nodes to a dropdown list

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C#

ASP.NET

XML

DropDownList

I have a drop downlist with xml files. when i select 1 from there i need to populate another dropdown list with just the nodes..

my c# code that populates the 1st dropdown with the xml files

protected void Page_Load(object sender, EventArgs e)
    {

        DirectoryInfo dirInfo = new DirectoryInfo(Server.MapPath("/Xmlscripts"));
        lblFolderLocation.Text = dirInfo.ToString(); // displays the folder location in a lable
        FileInfo[] fileList = dirInfo.GetFiles();
        foreach (FileInfo fileInfo in fileList)
        {
            dropdownlist1.Items.Add(new ListItem(fileInfo.Name, fileInfo.Name));
        }
}

I need help populating the second dropdown list with the nodes of the xml file when selected

Example of xml file below

<Script>
  <greeting> // need to display in second drop box
    <data>hi how you</data>
  </greeting>
  <verification> // need to display in second drop box
     <data> can i confirm it is Mike</data>
  </verification>
  <dropOf> // need to display in second drop box
    <data>when can i drop off?</data>
  </dropOf>
  <infoRequired> // need to display in second drop box
     <data>need the proof of payment</data>
  </infoRequired>
  <example> // need to display in second drop box
    <data> till slip</data>
  </example>
  <end> // need to display in second drop box
     <data>Thank you</data>
  </end>
</Script>

I want to add just the greeting, verification, dropOf, infoRequired, example, and end to the second dropdown list so when i click on one of them it will be able to display in a textbox.