The attached source code shows how to build an XML Parser using System.Xml classes. Some of the functionality this attached source code hows are - 
- Building XML object 
- Loading XML documents from string and/or XML files 
- Selecting a document node using SelectSingleNode 
- Selecting and retrieving a document nodes using ChildNode 
- Selecting and retrieving parent node of a selected node using ParentNode. 
- Navigating through a node siblings 
Download and run the attached source code for more details.