Create loops and parsing XML nodes value for Selenium tests

I am trying to write a test function in C# that read data from an XML file and parse into Selenium testing methods , the XML code is like:

<home>
   <ask_frame>    
      <id>Object ID<id>
      <xpath>Object XPath<xpath>
   </ask_frame>
   <search_frame>
      <id>Object ID<id>
      <xpath>Object XPath<xpath>
   </search_frame>
<home>

I am trying to create a loop that read the id and xpath value from these nodes and parse them into an method for searching a webpage element by id and xpath. My initial attempt was:

            XmlDocument xd = new XmlDocument();
            xd.Load(@"C:\XMLFile1.xml");
            XmlNodeList mainlist = xd.SelectNodes("home");
            XmlNodeList idlist = xd.SelectNodes("id");
            XmlNodeList xpathlist = xd.SelectNodes("XPath");
            XmlNode mainroot = mainlist[0];
            XmlNode idroot = idlist[0];
            XmlNode pathroot = xpathlist[0];

            foreach (XmlNode xnode in mainroot.ChildNodes)
            {
                string objID = idroot.InnerText;
                string objXPath = pathroot.InnerText;
                objectCheck(objID, objXPath);
           }   

However this is incorrect and throws an "Object reference not set to an instance of an object" error. I am still very new to C# , so any suggestions or hints for this problem will be highly appreciated.