How to read and write XML in .Net

The .NET Framework XML classes are made available through various System Namespaces. The core classes are available in System.Xml namespace. XmlReader and XMLWriter are the two abstract classes at the core of .NET Framework XML classes. These two classes define the common functionality that all derived classes must support. XmlReader provides a fast, forward-only, read-only cursor for processing an XML document stream. XmlWriter provides an interface for producing XML document streams that conform to the W3C's XML 1.0 and Namespaces Recommendations. So, if you are writing code to read XML documents, use XmlReader, and to create XML documents, use XmlWriter.

1. XmlTextReader (a class derived from XmlReader) supports reading XML documents from a text-based stream, while XmlTextWriter (a class derived from XmlWriter) allows writing XML documents to a text-based stream.
   
2. XmlNodeReader (a class derived from XmlReader) supports reading XML documents as in-memory DOM tree , while XmlNodeWriter (a class derived from XmlWriter) allows writing XML documents as in-memory trees.
   

Sample XML:

<? xml version="1.0" encoding="utf-16"?>
< CameraStore ID="Hunts-Camera-Store" >
    <location >Malden, MA </location>
    < inventory>
         <Camera  ID="Canon-Sure-Shot-Z155" >
             <fstop> 4.8-11.7</ fstop>
             <focallength >4-155mm zoom</ focallength >
            <cost > $318 USD</cost >
         </Camera>
        < Camera ID="Olympus-mju-II" >
             <fstop >4.8 </fstop>
            < focallength>mm </focallength >
            < cost> $178 USD</ cost>
         </Camera >
    </ inventory>
</CameraStore >

Here I will write a demo project with the sample Xml which has the following functions:

1. Create object instance with the data from sample xml using XmlTextReader
2. Save data of object instances to xml using XmlTextWriter

Download all project code from here!

CameraStore Class is the demonstration of XML CameraStore element  section:

Camera Class is the demonstration of XML Camera element  section:



Here is the code implementation:

/*
 * Created By HOME
 * User: BPLOVEGCY
 * Date: 2007-6-14
 * Time: 16:22
 * 
 *  http://bplovegcy.blogspot.com/
 * 
 */

using  System;
using System.Collections.Generic;
using  System.Xml;
using System.IO;
using  System.Text ;
using System.Collections;

namespace  XMLTesting
{
    /// <summary>
     /// Description of CameraStore.
     ///  </summary>
     public  class CameraStore
    {
        public  CameraStore(){}

        string id;
         string location;
        List<Camera>  cameraList;

         public string  ID
        {
             get { return id; }
             set { id = value; }
        }    

         public string Location
        {
             get { return location; }
             set  { location = value; }
        }        

         public List<Camera >  CameraList
        {
            get {  return  cameraList; }
            set { cameraList  = value; }
        }
        
        public  override  string ToString()
        {
            StringBuilder builder  =  new StringBuilder();
            builder.AppendLine( string .Format(@"id={0},location={1}" ,id,location));
            foreach(Camera camera in  cameraList)
            {
                builder.AppendLine(camera.ToString());
            }
            return  builder.ToString();
        }
        
        /// <summary>
        /// Assume the file full path has valid format
         ///  </summary>
        ///   <param name="fileFullPath"></param>
         public void ToXmlFile( string  fileFullPath)
        {
            if(fileFullPath  ==  null ||  fileFullPath  == string.Empty )
                 throw  new ArgumentNullException();
            
            XmlTextWriter xmlWriter  = new XmlTextWriter(fileFullPath, System.Text.Encoding.Unicode);
             // show xml declaration <?xml version="1.0" encoding="utf-16"?>            
            xmlWriter.WriteStartDocument();
            
            //  <CameraStore>
            xmlWriter.WriteStartElement(" CameraStore ");
            
            xmlWriter.WriteAttributeString(" ID ",id);
            xmlWriter.WriteElementString(" location ",location);
            
             // <inventory>
            xmlWriter.WriteStartElement( "inventory ");
            foreach (Camera camera in  cameraList)
            {
                camera.ToXml(xmlWriter);
            }
            // </inventory>
             xmlWriter.WriteEndElement();
            
             //</CameraStore>
            xmlWriter.WriteEndElement();
             // corresponding the xml declaration
            xmlWriter.WriteEndDocument();
             //  save the content to file
            xmlWriter.Close ();
        }
        
         /// <summary>
        ///  Assume the file full path has valid format
        ///   </summary>
        ///  <param name="fileFullPath"></param>
        ///  <returns></returns>
         public  static CameraStore ParseFromXML(string  fileFullPath)
        {
             try
            {
                CameraStore store  =  new CameraStore();
                 if(! File.Exists(fileFullPath))
                     throw new  ArgumentException(" The file doesn't exist!" );
                
                System.Xml.XmlTextReader xmlReader
                     =  new XmlTextReader(fileFullPath);
                
                while(xmlReader.Read ()){
                    if (xmlReader.NodeType ==  XmlNodeType.Element){
                        switch (xmlReader.Name)
                        {
                             case " CameraStore ":
                                if (xmlReader.HasAttributes){
                                     if(xmlReader.MoveToAttribute( "ID ")) store.id  =  xmlReader.Value;
                                }
                                break ;
                             case " location ":
                                store.location =  xmlReader.ReadString();
                                 break;
                                
                             case  "inventory ":
                                 store.cameraList = Camera.ParseFromXML(xmlReader);
                                break ;
                        }
                    }
                }
                 return  store;
            } catch(Exception ex){
                 throw  ex;
            }
            
        }
    }
    public  class  Camera
    {
        string id;
         string  fstop;
        string focallength;
         string  cost;

        public Camera(){}        

        public  string ID
        {
            get {  return id; }
             set { id  = value; }
        }

         public string  Fstop
        {
            get  { return  fstop; }
            set  { fstop =  value; }
        }

        public  string  Focallength
        {
            get  { return  focallength; }
            set { focallength  =  value; }
        }

        public  string  Cost
        {
            get {  return cost; }
            set { cost =  value; }
        }

        public override   string ToString()
        {
            return   string.Format("id={0},fstop={1},focallength={2},cost={3} ",
                                 id,fstop,focallength,cost);
        }
        
         public  static List< Camera > ParseFromXML(XmlTextReader xmlReader)
        {
            List< Camera > cameraList =  new  List<Camera> ();
            Camera camera  = null;
             while(xmlReader.Read()){
                if(xmlReader.NodeType   == XmlNodeType.Element){
                    switch (xmlReader.Name)
                    {
                        case " Camera ":
                            camera =   new Camera();
                            //  get the attribute id
                            if (xmlReader.HasAttributes  && xmlReader.MoveToAttribute(" ID" )){
                                camera.id  =  xmlReader.Value;
                            }
                            break;
                         case "fstop ":
                            // here to get a element value use the read string
                            // get attribute value first move to the attribute then get the value
                            camera.fstop = xmlReader.ReadString();
                             break;
                        case  "focallength":
                            camera.focallength  = xmlReader.ReadString();
                            break;
                         case "cost " :
                            camera.cost = xmlReader.ReadString();
                             break;
                        default:
                             // nothing just move next
                             break;
                    }
                } else  if( xmlReader.NodeType == XmlNodeType.EndElement
                          && xmlReader.Name ==  "Camera")
                     if( camera != null ) cameraList.Add(camera);
            }
            return cameraList;
        }
        
         public void ToXml(XmlTextWriter xmlWriter)
        {
             if(xmlWriter == null )
                throw new ArgumentNullException();
            xmlWriter.WriteStartElement("Camera" );
            
            xmlWriter.WriteAttributeString("ID" ,id);
            
            xmlWriter.WriteElementString("fstop" ,fstop);
            
            xmlWriter.WriteElementString("focallength" ,focallength);
            
            xmlWriter.WriteElementString("cost ",cost);
            //</Camera>
            xmlWriter.WriteEndElement();
        }
    }
}

Here is the testing code (NUnit framework):

/*
 * Created By HOME
 * User: BPLOVEGCY
 * Date: 2007-6-14
 * Time: 17:02
 * 
 *  http://bplovegcy.blogspot.com/
 * 
  */

using  NUnit.Framework;
using  System;
using System.Reflection ;
using  System.IO;
using System.Resources;

namespace  XMLTesting
{
    [TestFixture]
    public  class  Testing
    {        
        [Test]
        public  void  TestMethod()
        {
            //  Please modify the path pointing to the location of the CameraStore.xml
            string  xmlFilePath =  @" C:\CameraStore.xml";
            CameraStore store  =  CameraStore.ParseFromXML(xmlFilePath);
            Console.WriteLine(store.ToString());
            
             const  string FilePath =   "c:\\testing.xml";
            store.ToXmlFile (FilePath);
        }
    }
}

--
Happy day, happy life!