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A Final Example

We have the XML defined, and you're now a bit more familiar with the System.Xml namespaces. Copy and paste the code below into a file under <webroot>/bin/test.cs. Create the bin directory, if it does not already exist, because .NET searches for namespaces by default in <webroot>/bin. Listing 4 provides the code that will be used in the custom namespace.

Listing 4: Namespace for Supporting Classes

namespace test
{
   using System;
   using System.Collections;
   using System.Xml;
   using System.Xml.XPath;

   public class Contact
   {
     public Contact()
     {
        szFirstName = String.Empty;
        szLastName  = String.Empty;
        szMiddleName = String.Empty;
     }
     
     public Contact(XPathNavigator oNav, String szId)
     {
        // Grab the contact info and initialize the data [ccc]
members with it. 
        XPathNodeIterator oIterator = oNav.Select[ccc]
("personal_information/contacts/entry[@id='" + szId + "']");
        oIterator.MoveNext();


        XPathNodeIterator oName = oIterator.Current.Select[ccc]
("./name");
        oName.MoveNext();

        szFirstName = GetAttributeText(oName.Current, "first");
        szMiddleName = GetAttributeText(oName.Current, "middle");
        szLastName  = GetAttributeText(oName.Current, "last");
        szInitials  = String.Empty;
        szKeywords  = String.Empty;

        if (GetAttributeText(oName.Current, "gender") == "f")
        {
          szGender = "Female";
        } else {
          szGender = "Male";
        }


        //TODO: Addresses
        oAddresses = new Hashtable();

        Address oHome = new Address(oIterator.Current, "home");
        Address oWork = new Address(oIterator.Current, "work");
        oAddresses.Add("home", oHome);
        oAddresses.Add("work", oWork);

        //TODO: Phone Number
        oPhones = new Hashtable();

        PhoneNumber oPHome = new PhoneNumber(oIterator.[ccc]
Current, "home");
        PhoneNumber oPWork = new PhoneNumber(oIterator.[ccc]
Current, "work");

        oPhones.Add("home", oPHome);
        oPhones.Add("work", oPWork);

     }
     
     public PhoneNumber GetPhoneNumber(String szType)
     {
        return (PhoneNumber) oPhones[szType];
     }

     public Address GetAddress(String szType)
     {
        return (Address) oAddresses[szType];
     }

     private String GetAttributeText(XPathNavigator nav, [ccc]
String szName)
     {
        String szRetval = String.Empty;

        nav.MoveToAttribute(szName, "");
        szRetval = nav.Value;
        nav.MoveToParent();

        return szRetval;
     }

     public String szFirstName;
     public String szMiddleName;
     public String szLastName;
     public String szGender;
     public String szKeywords;
     public String szInitials;

     private Hashtable oAddresses;
     private Hashtable oPhones;
   }

   
   public class Address
   {
     public Address(XPathNavigator oNav, String szType)
     {
        try
        {
          szState = String.Empty;
          szCity = String.Empty;
          szZip  = String.Empty;

          XPathExpression oExpr;
          String szExpr = String.Empty;

          szExpr = "./address[@type='" + szType + "']/line";
          oExpr = oNav.Compile(szExpr);
          
          // Create comparison class for the ISBN number
          ContactCompare oAddressCompare = new [ccc]
ContactCompare();

          // Add a comparer to do a string compare on the [ccc]
ISBN number
          oExpr.AddSort("@seq", (IComparer)oAddressCompare);

          XPathNodeIterator oIterator = oNav.Select(oExpr);
          int x = 0;

          aLines = new String[oIterator.Count];

          while (oIterator.MoveNext())
          {
             aLines[x] = oIterator.Current.Value;
             x++;
          }

          szExpr = "./address[@type='" + szType + "']/city";
          
          oIterator = oNav.Select(szExpr);
          oIterator.MoveNext();
          szCity = oIterator.Current.Value;
          
          szExpr  = "./address[@type='" + szType + "'][ccc]
/state";
          oIterator = oNav.Select(szExpr);
          oIterator.MoveNext();

          szState = oIterator.Current.Value;

          szExpr  = "./address[@type='" + szType + "'][ccc]
/zipcode";
          oIterator = oNav.Select(szExpr);
          oIterator.MoveNext();
        
          szZip = oIterator.Current.Value;
          oIterator.Current.MoveToParent();
        }
        catch (ArgumentException ex)
        {
          String blah = ex.Message;
          szState = String.Empty;
          szCity = String.Empty;
          szZip  = String.Empty;

        }
     }

     public String[] aLines;
     public String szState;
     public String szCity;
     public String szZip;
   }
   
   // does a string compare. used with XPathExpression
   class ContactCompare : IComparer
   {
     public int Compare(Object First, Object Second)
     {
        String s1 = (String) First;
        String s2 = (String) Second;

        return s1.ToString().CompareTo(s2.ToString());
     }

   }
   
   // contains a phone number
   public class PhoneNumber
   {
     public PhoneNumber(XPathNavigator oNav, String szType)	
     {

        String szExpr = String.Empty;
        szExpr = "./phone[@type='" + szType + "']";

        XPathNodeIterator oIterator = oNav.Select(szExpr);

        oIterator.MoveNext();
        
        szACode = GetAttributeText(oIterator.Current, [ccc]
"acode"); 
        szNumber = GetAttributeText(oIterator.Current, [ccc]
"number");
     }

     private String GetAttributeText(XPathNavigator nav, [ccc]
String szName)
     {
        String szRetval = String.Empty;

        nav.MoveToAttribute(szName, "");
        szRetval = nav.Value;
        nav.MoveToParent();

        return szRetval;
     }
     
     public String szACode;
     public String szNumber;
   }

   // Only manages one contacts xml file at a time. 
   public class ContactManager
   {
     public ContactManager(String szFilePath)
     {
        // Initialize the XPath classes.
        oDoc = new XmlDocument();
        oDoc.Load(szFilePath);
        oNav = oDoc.CreateNavigator();
        oNav.MoveToRoot();

        // Get a count of all entries.
        XPathNodeIterator oIterator = oNav.Select[ccc]
("personal_information/contacts/entry");
        iContactCtr = oIterator.Count;

     }

     public Contact GetContact(String szId)
     {
        Contact pTemp = new Contact(oNav, szId);
        return pTemp;
     }

     public Contact GetContact(int Id)
     {
        Contact pTemp = new Contact(oNav, Convert.ToString(Id));
        return pTemp;
     }

     public int Count()
     {
        return iContactCtr;
     }

     private XPathNavigator oNav;
     private XmlDocument  oDoc;
     private int         iContactCtr;
   }

}

Compile the C# file on the command line from the bin directory, which should be located off your working Web root. Run this command to build the code into a namespace:

csc /t:library /r:System.dll /r:System.Data.dll /r:System.Web.dll [ccc]
/r:System.Xml.dll test_lib.cs

If you're an experienced .NET developer, most of this code should be familiar. The ContactManager class is used to accomplish any management tasks, such as getting contacts and counting contacts. The contact class provides an interface into the data. A problem with the current version is that all the variables for storing contact information are declared public. On the plus side, you have the capability to do sorts with the XPathExpression class itself. This class is used minimally in the Address class, but it demonstrates functionality that current XPath implementations do not contain. First, the comparison class is defined:

   class ContactCompare : IComparer
   {
     public int Compare(Object First, Object Second)
     {
        String s1 = (String) First;
        String s2 = (String) Second;

        return s1.ToString().CompareTo(s2.ToString());
     }

   }

Then the user-defined comparison class is used with an XPath selection of sorts. In our case, this is the Address class to sort the line nodes by the seq attribute:

...
   XPathExpression oExpr;
   String szExpr = String.Empty;

   szExpr = "./address[@type='" + szType + "']/line";
   oExpr = oNav.Compile(szExpr);
   
   // Create comparison class for the ISBN number
   ContactCompare oAddressCompare = new ContactCompare();

   // Add a comparer to do a string compare on the ISBN number
   oExpr.AddSort("@seq", (IComparer)oAddressCompare);

   XPathNodeIterator oIterator = oNav.Select(oExpr);
...

The sorting capabilities in XPathExpression are welcome addition to the System.Xml.XPath namespace. A developer actually has another option to do, rather than fumbling through XSL to complete the job.

The design is simple and meets our needs of providing an interface into the data. Because both classes are contained in a namespace, building a Web Service on top of any functionality would be trivial with .NET. If there aren't any compiler errors, let's proceed to actually build out a Web page to use the namespace.

All the real data work is done in the namespace, which makes the Web page itself very simple. Of course, that is the purpose of abstracting the work away from the UI (see Listing 5).

Listing 5: Using the Supporting Test Namespace to Build an HTML Page for a User

<%@Page language="C#" %>
<%@Import Namespace="test" %>

<html>
<script runat="server">
   XPathDocument myXPathDocument;
   ContactManager oMgr;

   void Page_Load(Object sender, EventArgs e)
   {
     oMgr = new ContactManager(Server.MapPath("contacts.xml"));

     int iCtr = oMgr.Count();
     
     for(int x = 0; x < iCtr; x++)
     {
        Contact pTemp = oMgr.GetContact(x);
        Response.Write(pTemp.szFirstName + " " + [ccc]
pTemp.szMiddleName + " " + pTemp.szLastName + "<br>");

        Address oHomeAddress = pTemp.GetAddress("home");
        DisplayAddress(oHomeAddress);
        Response.Write("<br>");

        PhoneNumber oWorkPhone = pTemp.GetPhoneNumber("work");
        PhoneNumber oHomePhone = pTemp.GetPhoneNumber("home");

        Response.Write("Work =");
        DisplayPhone(oWorkPhone);
        Response.Write("<br>");

        Response.Write("Home =");
        DisplayPhone(oHomePhone);
        Response.Write("<br><br>");
     }
   }

   private void DisplayAddress(Address oData)
   {
     for (int i = 0; i < oData.aLines.Length; i++)
     {
        Response.Write(oData.aLines[i] + "<br>");
     }
   
     Response.Write(oData.szCity + "," + oData.szState + [ccc]
"&nbsp;&nbsp;&nbsp;&nbsp;" + oData.szZip);
   }

   private void DisplayPhone(PhoneNumber oData)
   {
     Response.Write("(" + oData.szACode + ")" + oData.szNumber);
   }


   private void DisplayName(XPathNavigator nav)
   {
     String szExpr = String.Empty;
    szExpr = "name";

    XPathNodeIterator oIterator = nav.SelectChildren(szExpr, "");
     oIterator.MoveNext();

     Response.Write(GetAttributeText(oIterator.Current, "first"));
     Response.Write(" " + GetAttributeText(oIterator.Current, [ccc]
"middle"));
     Response.Write(" " + GetAttributeText(oIterator.Current, [ccc]
"last") + "<br>");
   }

</script>
<body>
</body>
</html>

This simple Web page to use the classes in the test namespace is fairly self-explanatory. First, the XML data file is initialized with the proper file. From that point, the count of entry nodes is obtained and the loop just goes through them one by one, displaying the relevant information. This is a nice exercise in accessing custom namespaces, but it's nothing revolutionary. The namespace created earlier is the true workhorse of this example. The XmlDocument was used mostly for its capability to edit as well as select data. The XPathDocument could've been used, but it allows only read-only access. We still can use XPath itself and even can create a XPathNavigator class for use with XSL as well. Because .NET's XML classes are integrated at key levels, it becomes very easy to switch this code from XmlDocument to XPathDocument if we feel the need for speed vs. the extra functionality of XmlDocument. Really, what has been done is that we've used classes that suit the needs of the application—and that is truly what you need to do when building an application in a new platform.

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