Reading an XML File using .NET

• Download demo project - 11 KB

Introduction

In this article, we will see how we can read an XML file in our ASP.NET application. This trick is useful for making custom configuration files for your application or just reading data stored in an XML file.

Overview

This code uses the XmlTextReader object to read the disk file into the XmlDocument object. The XmlTextReader object has very similar functionality to the StreamReader and BinaryReader objects, except that it is specifically designed to read XML file. The XmlTextReader object also has other XML-specific features. For example, the WhitespaceHandling property setting in the code tells it not to create nodes for extra whitespace in the XML file.

The code uses the DocumentElement property of the XmlDocument object to find the node at the root of the tree representation of the XML document. After that, we just recursively call the procedure that adds information about the node to the ListBox control.

The code also deals with attributes. Attributes nodes are not included in the ChildNodes collection of a node in the XmlDocument object. Instead, you can use the Attributes property of the XmlNode object to get a collection of attribute nodes only. The code uses an XmlNamedNodeMap object to hold this collection; this object can hold an arbitrary collection of XmlNode objects of any type.

Code Listing

  private void btnLoad_Click(object sender, System.EventArgs e)
  {
    XmlTextReader reader = new XmlTextReader(
      Server.MapPath("mycompany.xml"));

    reader.WhitespaceHandling = WhitespaceHandling.None;
    XmlDocument xmlDoc = new XmlDocument();
    //Load the file into the XmlDocument
    xmlDoc.Load(reader);
    //Close off the connection to the file.
    reader.Close();
    //Add an item representing the document to the listbox
    lbNodes.Items.Add("XML Document");
    //Find the root node, and add it together with its childeren
    XmlNode xnod = xmlDoc.DocumentElement;
    AddWithChildren(xnod,1);
  }

  private void AddWithChildren(XmlNode xnod, Int32 intLevel)
  {
    //Adds a node to the ListBox, together with its children.
    //intLevel controls the depth of indenting
    XmlNode xnodWorking;
    String strIndent = new string(' ',2 * intLevel);
    //Get the value of the node (if any)
    string strValue = (string) xnod.Value;
    if(strValue != null)
    {
      strValue = " : " + strValue;
    }
    //Add the node details to the ListBox
    lbNodes.Items.Add(strIndent + xnod.Name + strValue);

    //For an element node, retrieve the attributes
    if (xnod.NodeType == XmlNodeType.Element)
    {
      XmlNamedNodeMap mapAttributes = xnod.Attributes;
      //Add the attributes to the ListBox
      foreach(XmlNode xnodAttribute in mapAttributes)
      {
        lbNodes.Items.Add(strIndent + " " + xnodAttribute.Name +
          " : " + xnodAttribute.Value);
      }
      //If there are any child node, call this procedure recursively
      if(xnod.HasChildNodes)
      {
        xnodWorking = xnod.FirstChild;
        while (xnodWorking != null)
        {
          AddWithChildren(xnodWorking, intLevel +1);
          xnodWorking = xnodWorking.NextSibling;
        }
      }
    }
  }
}

License

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