cannot access object of class XmlDocument on C#

I was trying to write an automatic method that retrieve a value from an XML file.

as i wrote the following code:

XmlDocument xDoc = new XmlDocument();

I found out that when I'm trying to access xDoc object while typing xDoc. , it does nothing, means no option to manipulate the object...

my usings are:

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using Microsoft.Office.Interop;
using System.IO;
using Excel = Microsoft.Office.Interop.Excel;
using System.Xml;
using System.Collections.Generic;

Any ideas ?

thx,