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Simple JSON handler for ASP.NET 2.0 to implement AJAX functionality

, 1 Jul 2011 CPOL
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Simple JSON handler for ASP.NET 2.0 to implement AJAX functionality
This is an old version of the currently published article.

Introduction

This article described how to use AJAX functionality using the popular JavaScript library (jQuery) with a minimal amount of code without using ASP.NET 2.0 AJAX tool kit. ASP.NET 2.0 does not support JSON so this will help if you want to use ASP.NET 2.0.

This example has two drop down controls whereas customer and customer description. Customer description will be loaded when customer drop down change without reloading the entire page.

AJAX.JPG


Using the code

AJAXProjectTree.JPG

  • Jquary library files need to be included to the project as shown above.

These are the library files

  • jquery-1.4.1-vsdoc.js,jquery-1.4.1.js,
  • query-1.4.1.min.js,
  • jquery-1.5.2.min.js,
  • jquery-ui-1.8.11.custom.min.js
Sample_ajax.js file will have Ajax implementation using the Jquary
var ajax = {

    setDebugMode: function(){
        this.debugMode = true;
    },

    get: function (requestUrl, data, loaderImageId, onSuccess, onComplete) {

        if (loaderImageId) {
            $("#" + loaderImageId).css('display', 'inline');
        }

        var completeFunction = function () {
            if (onComplete) {
                onComplete();
            }
            if (loaderImageId) {
                $("#" + loaderImageId).css('display', 'none');
            }
        };

        $.ajax({
            type: "GET",
            url: requestUrl,
            data: data,
            context: this,
            success: function (response) {
                onSuccess(response);
                completeFunction();
            },
            error: function (response) {
                alert("Ajax Request Failed");
                this.showError(response);
                completeFunction();
            }
        });
    },

    post: function (requestUrl, data, loaderImageId, onSuccess, onComplete) {

        if (loaderImageId) {
            $("#" + loaderImageId).css('display', 'inline');
        }

        var completeFunction = function () {
            if (onComplete) {
                onComplete();
            }
            if (loaderImageId) {
                $("#" + loaderImageId).css('display', 'none');
            }
        };

        $.ajax({
            type: "POST",
            url: requestUrl,
            context: this,
            data: data,
            success: function (response) {
                onSuccess(response);
                completeFunction();
            },
            error: function (response) {
                alert("Ajax Request Failed");
                this.showError(response);
                completeFunction();
            }
        });
    },

    showError: function(requestObject){
        if (this.debugMode){
            alert(requestObject.responseText);
        }
    }
};
         

ASPX Page(SampleAjax.aspx)

Include the java script as below

<script type="text/javascript" src='<%= this.ResolveUrl("~/Scripts/jquery-1.5.2.min.js")%>' ></script>
<script type="text/javascript" src='<%= this.ResolveUrl("~/Scripts/jquery-ui-1.8.11.custom.min.js")%>' ></script>
<script type="text/javascript" src='<%= this.ResolveUrl("~/Scripts/sample_ajax.js")%>' ></script>         

Write Java script to call customer descriptions when customer drop down change

     <script type="text/javascript">
     <% if (SampleJSONWeb.ConfigurationData.DebugMode){ %>
                    ajax.setDebugMode();
            <%} %>
    $(document).ready(function () 
    {
        $("#<%= customerDropDown.ClientID %>").change(function () 
        {
                var customerTypeId = $('#<%= customerDropDown.ClientID %>').val();
                ajax.get('<%= this.ResolveUrl("~/LoadCustomerDescriptions.ashx")%>',
                    { 'customerTypeId': customerTypeId },
                    'CustomerDescriptionsLoader',
                        function (response) 
                        {
                            $('#<%= customerDescriptionDropDown.ClientID %> option').remove();
                            for (var i = 0; i < response.Data.length; i++) 
                            {
                                $('#<%= customerDescriptionDropDown.ClientID %>').append(getOptionString(response.Data[i]));
                            }
                        }
                    );
            });
    
    
        function getOptionString(dataElement)
        {
          return "<option value='"+dataElement.Id+"' >"+dataElement.Name+"</option>";
        }
    });

</script>     

LoadCustomerDescriptions.ashx will be invoked by above java script.

   public class LoadCustomerDescriptions : JsonRequestHandler
    {
        public override void ProcessRequest(HttpContext context)
        {
            string customerTypeId = context.Request.QueryString["customerTypeId"].ToString();

            //load data
            GetData getData = new GetData();
            IList<ReferenceData> data = getData.GetCustomerescriptions(customerTypeId);

            //Insert an empty row as the first row
            data.Insert(0, new ReferenceData(string.Empty, string.Empty));

            //return as JSON result
            Dictionary<string, string> response = new Dictionary<string, string>();
            response.Add("Data", GetJsonCollection<ReferenceData>(data));
            SetResponse(context, response);
        }
    }         

The above method get the data from back end and send back as JSON format. JSON handler has the implementation to manage JSON data as below

using System;
using System.Collections.Generic;
using System.Web;
using System.Text;
using System.Reflection;
using System.Web.SessionState;

namespace SampleJSONWeb
{
    public abstract class JsonRequestHandler : IHttpHandler, IRequiresSessionState
    {

        public abstract void ProcessRequest(HttpContext context);

        protected void SetResponse(HttpContext context, string jsonResponse)
        {
            context.Response.Cache.SetExpires(DateTime.Now);
            context.Response.ContentType = "application/json";
            context.Response.Write(jsonResponse);
            context.Response.End();
        }

        protected void SetResponse(HttpContext context, Dictionary<string, string> attributes)
        {
            SetResponse(context, GetJsonObject(attributes));
        }

        protected void SetResponse<T>(HttpContext context, T obj)
        {
            SetResponse(context, GetJsonObject<T>(obj));
        }

        protected T CreateObjectFromRequest<T>(HttpContext context) where T: new()
        {
            T ob = new T();
            PropertyInfo[] properties = typeof(T).GetProperties();
            foreach (PropertyInfo property in properties)
            {
                string value = context.Request.Params[property.Name];
                if (value == null)
                {
                    continue;
                }

                if (property.PropertyType != typeof(string) && value == string.Empty)
                {
                    continue;
                }

                object convertedValue = Convert.ChangeType(value, property.PropertyType);
                if (convertedValue == null)
                {
                    continue;
                }

                property.SetValue(ob, convertedValue, null);
            }
            return ob;
        }

        protected string GetJsonObject(Dictionary<string, string> attributes)
        {
            StringBuilder jsonBuilder = new StringBuilder();
            jsonBuilder.Append("{");
            bool firstTime = true;
            foreach (string key in attributes.Keys)
            {
                if (!firstTime)
                {
                    jsonBuilder.Append(",");
                }

                string name = key;
                object value = attributes[key];
                jsonBuilder.Append("\"" + name + "\":" + value.ToString());
                firstTime = false;
            }
            jsonBuilder.Append("}");
            return jsonBuilder.ToString();
        }

        protected string GetJsonCollection<T>(IEnumerable<T> collection)
        {
            StringBuilder jsonBuilder = new StringBuilder();
            jsonBuilder.Append("[");

            bool first = true;
            foreach (T item in collection)
            {
                if (!first)
                {
                    jsonBuilder.Append(",");
                }
                jsonBuilder.Append(GetJsonObject<T>(item));
                first = false;
            }

            jsonBuilder.Append("]");
            return jsonBuilder.ToString();
        }

        protected string GetJsonObject<T>(T obj)
        {
            PropertyInfo[] properties = typeof(T).GetProperties();
            StringBuilder jsonBuilder = new StringBuilder();
            jsonBuilder.Append("{");
            bool firstTime = true;
            foreach (PropertyInfo property in properties)
            {
                if (!firstTime)
                {
                    jsonBuilder.Append(",");
                }

                string name = property.Name;
                object value = property.GetValue(obj, null);
                jsonBuilder.Append("\"" + name + "\":\"" + value.ToString() + "\"");
                firstTime = false;
            }
            jsonBuilder.Append("}");
            return jsonBuilder.ToString();
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}     

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Pubudu Kasakara
Architect
Singapore Singapore
Pubudu Kasakara is working as Solution Architect in Singapore. He has more than 11 years of professional involvement in the IT industry. Worked in successful projects involving mainly the Service Oriented Application by contributing to all requirements gathering, design and implementation phases. He is having experience with SOA applications development, Microsoft .NET, BizTalk, He is member of Charted It professional in UK.
 
Solution Architect
http://www.kasakara.com

Comments and Discussions


Discussions posted for the Published version of this article. Posting a message here will take you to the publicly available article in order to continue your conversation in public.
 
QuestionIs there any third party tools which support JSON in asp.net 2.0. I have also mentioned my task below. Pinmembermanojnatarajan16-Oct-11 19:46 
GeneralMy vote of 4 PinmemberHamlet Escaño1-Jul-11 11:26 
GeneralRe: My vote of 4 PinmemberPubudu Kasakara2-Jul-11 18:59 
Generalgood article but implementation is complecated Pinmembermike231515-Jun-11 4:58 
GeneralRe: good article but implementation is complecated PinmemberPubudu Kasakara1-Jul-11 0:19 
GeneralMy Vote of 4 Pinmemberasp_crazy_guy15-Jun-11 0:01 
GeneralMy vote of 5 PinmemberMonjurul Habib14-Jun-11 12:14 
GeneralLots of hoops... PinmemberOnskee114-Jun-11 4:03 
GeneralRe: Lots of hoops... PinmemberPubudu Kasakara1-Jul-11 0:20 
GeneralRe: Lots of hoops... PinmemberOnskee11-Jul-11 9:16 

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