Rating Demystified: Ajax Way, Amazon Way*

• Download source files - 160 Kb

Online demo - Ajax Rating (updated)

Get the Rating Web Widget (new)

Introduction

This article describes an ASP.NET web module along with some chunks of Javascripts and ...Ajax to create a Rating System. This can be added /customized for any table to add a rating/score module. I was quite amazed, when i first saw the capability of rating multiple items at amazon website without refreshing the page. That nice piece of functionality followed me like destiny, till i needed to implement it in a web application.

Well ! putting it in a live scenario needs much more than just javascript. I started with a bit of frenzied hacking. To understand how exactly it works, by scanning the javascript from online asynchronous rating websites. That was just the beginning, on the way i learned much more than earlier imagined. Here is the result of the effort.

The target was to create a cross browser rating/score system like amazon or better:

1. Rating: User should be able to Rate a record (1-5)
2. Accuracy: Number of votes and total score should be accurate and saved and should not be lost in calculations
3. Real time: Rate/score should be displayed after rating instantly
4. Reusable: It should be easily plugged into any table for reusability
5. Avoiding multiple ratings: Basic mechanism to avoid multiple ratings by the same user
6. Best approach: Compare the pros and cons for both Amazon and Ajax approach
7. Security: Few words

_{* By Amazon Way i meant it can simulate the rating system like the amazon website, it does not claims that this is the way amazon is doing there rating.}

In Action

To hold your interest, here is how it will look (for single record), once completed

Assumptions

Those were the initial thoughts, but to make it a general reusable and extensible module, I made some assumptions:

• The table which will have the records to be rated will have a Primary Key ID (integer and identity) and the it will be the first field in the table.
• The Table will have atleast two Fields: RatedBy & Score
• For the current example to work you will need atleast one extra field Title

Rating table structure

web.config structure

The web.config has four keys, one for the connection string and the other for the name of the fields for RatedBy (for the number of user who rated the record) and Score (For total Score) and the table from which you want to apply the Rating system.

Required images ( included with the source)

Final Scores

Pretty self explainatory final score can be in decimals 1, 2.5, 2, 4.5 etc, though while rating the images should be only 1-5

Actions

These are the actions which make the whole module:

• Data access
• Create rolling mouseover rating images
• Rating Amazon way, Ajax way
• Saving asynchronously using IFrames like Amazon (needs refresh)
• Saving asynchronously using AJAX (no refresh)
• Rating multiple items in the same page
• Basic security, rating for an item can be done only once by the user

Data access class

There is a standard data access class, clsDataAccess.cs, which handles all the data related actions.

Code: I have kept here only the names of the functions, just to give you a glimpse of the data access methods.

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient; 

namespace Rating
{
    public class clsDataAccess
    // Class defination
    {
        public clsDataAccess()
        { }
        SqlConnection mycon = new SqlConnection(
          ConfigurationSettings.AppSettings["ConnectionString"]);
        // Opens database connection with in SQL SERVER
        public bool openConnection()
        // Closes database connection with in SQL SERVER
        public void closeConnection()
        // Getdata from the table required(given in query).
        public SqlDataReader getData(string query)
        // Save data usually,inserts and updates the data in table.
        public void saveData(string query)
        // Save data usually,inserts and updates the data.
        public void saveNewData(string query)
        // Delete data in database depending on the tablename.
        public int DeleteData(string query)
        // Get data by paging using datagrid.
        public SqlDataAdapter getDataforUpdate(string query)
        // Get data by paging using datagrid.
        public DataSet getDatabyPaging(string query)
        // check a particular value to see the validity.
        public int getCheck(string query)
        // Get a value of limit from the database table.
        public string getValue(string query,int j)
        //Log in method 
        public SqlDataReader Login(string query)
        // dynamically get all table names
        public DataTable getTablenames()
        // For Table operations
        public int TableWrite(string query)
    }
}

Creating rating Images with mouse over:

For this we need set of five images for the stars and five for the comments as shown above and two javascript function DisplayStars and DisplayMsg to display those images on mouseover.

Code

function DisplayStars (id, rating)
{
     var starID = "stars." + id;
     starTwinkler[id] = 0;
     msgTwinkler[id] = 0;
     document.write("<map name='starmap" + id +"'>");
     var i = 0;
     for (i = 1; i < 6; i++) {
     document.write("<area shape=rect " + 
     "coords='" + starMap[i] + "' " +
     "onMouseOver=\"StarMouseOver('" + id + "'," + i + ");\" " +
     "onMouseOut=\"StarMouseOut('" + id + "');\" " +
     "onClick=\"SaveStars('" + id + "'," + i + ");" +
     "\" >");
 }
 document.write("</map>");
 document.write("<img vspace=2 title = 'Rate Picture' src='" 
 + starImages[rating] + "'");
 document.write(" border=0 usemap='#starmap" + id);
 document.write("' id='" + starID + "'>");
}
function DisplayMsg (id, rating)
{
     var msgID = "messages." + id;
if ( rating == undefined ) {
document.write("<img vspace=2 height=11 src='" + nullStarMessage + "'");
    }
     else {
 document.write("<img vspace=2 height=11 src='" + starMessages[rating] + "'"); 
     }
 document.write("' id='" + msgID + "'>");
}

Javascript Mouseover functions are so old that nothing needs to be explained.You will also need functions for MouseOut OnClick, Initalize images etc, included in the source.

Rating: Amazon Way 

Amazon uses IFrames So the whole process of rating actually happens in another page which resides in the current page through iframe. Rate.aspx is the page which will be called inside an IFrame to call the Rating function