Streamlining the JSON Serialization

Thursday, 1 November 2007 03:26 by James

For a while now I have been using the Newtwonsoft.Json dll to generate my JSON objects. The documentation is pretty sparse and I had to do a lot of experimentation to figure out the best way to do it. I ended up with this base code.

myUCR_DepartmentsTableAdapters.MyUCR_DepartmentsTableAdapter deptTA = new myUCR_DepartmentsTableAdapters.MyUCR_DepartmentsTableAdapter();
myUCR_Departments.MyUCR_DepartmentsDataTable deptDT = new myUCR_Departments.MyUCR_DepartmentsDataTable();
deptTA.FillDepts(deptDT);
StringWriter sw = new StringWriter();
JsonWriter writer = new JsonWriter(sw);
writer.WriteStartArray();

foreach (myUCR_Departments.MyUCR_DepartmentsRow deptRow in deptDT)
{
   writer.WriteStartObject();
   writer.WritePropertyName("deptID"); writer.WriteValue(deptRow.deptID.ToString());
   writer.WritePropertyName("dept"); writer.WriteValue(deptRow.department.ToString().Trim());
   writer.WriteEndObject();           
}
writer.WriteEndArray();
writer.Flush();
Response.Write(sw.GetStringBuilder().ToString());

 As you can see, that's a lot of code to serialize a simple datatable.

I wanted to find an easier way, so started browsing around. Googling for "JSON DataTable Serialization", I came across this article "A DataTable Serializer for ASP.NET AJAX" at denydotnet.com. What he did was to extend the JavaScriptConverter found in System.Web.Script.Serialization to serialize a DataTable. I looked through his code and decided to implement it.

Now here's how I do my serialization:

        MyUCR_LoginTableAdapter ta = new MyUCR_LoginTableAdapter();
        DataTable dt = ta.GetByTesting();
        JavaScriptSerializer toJSON = new JavaScriptSerializer();
        toJSON.RegisterConverters(new JavaScriptConverter[]{new JavaScriptDataTableConverter()});
        Response.Write(toJSON.Serialize(dt));

And what rocks is the object names are mapped to the column names in the database.

Cool

James

 

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Categories:   Web Development | Ajax and Javascript
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Comments

May 27. 2008 21:46

Hi James,

Could you please let me know how can we use the returned data from the maethod in the javascript code.What is the best way to populate them into a HTML table.

Regards,
Kishore.

Kishore

May 28. 2008 01:07

Hi Kishore,
The data returned is in JSON format, so I have a function which converts the JSON formatted string to an Array.

function returnJson(rText)
{
    if(rText.indexOf(chk) > -1){rText = rText.substring(chk.length, rText.length);}
    var func = new Function("return " + rText);
    var jsonObj = func();
    return jsonObj;
}

After that it's just a matter of looping through the elements of the array and processing them. For instance:

var myString = jsonObj[i]["myString"];
Creating a table isn't difficult, just loop through the array, creating a row for each iteration, and a cell for each value in the that row.

Take a look at my "Home Grown Ajax presentation". And check out json.org for more information on the JSON format.

Thanks for the comment,
James

James Johnson

January 23. 2009 01:51

Hi,

Can you include the JavaScriptDataTableConverter() function?  I've been trying to locate the original article at dennydotnet.com but it seems the website is currently down.

Thanks.

Fredericke

January 23. 2009 02:53

here you go....

using System;
using System.Collections.Generic;
using System.Data;
using System.Configuration;
using System.Web;
//using System.Web.
using System.Web.Script.Serialization;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;


/// <summary>
/// Summary description for JavaScriptDataTableConverter
/// </summary>
///
public class JavaScriptDataTableConverter : JavaScriptConverter
{
    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        throw new NotImplementedException("Deserialize is not implemented.");
    }

    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
    {
        DataTable dt = obj as DataTable;
        Dictionary<string, object> result = new Dictionary<string, object>();

        if (dt != null && dt.Rows.Count > 0)
        {
            // List for row values
            List<object> rowValues = new List<object>();

            foreach (DataRow dr in dt.Rows)
            {
                // Dictionary for col name / col value
                Dictionary<string, object> colValues = new Dictionary<string, object>();

                foreach (DataColumn dc in dt.Columns)
                {
                    colValues.Add(dc.ColumnName, // col name
                     (string.Empty == dr[dc].ToString()) ? null : dr[dc]); // col value
                }

                // Add values to row
                rowValues.Add(colValues);
            }

            // Add rows to serialized object
            result["rows"] = rowValues;
        }

        return result;
    }

    public override IEnumerable<Type> SupportedTypes
    {
        //Define the DataTable as a supported type.
        get
        {
            return new System.Collections.ObjectModel.ReadOnlyCollection<Type>(
             new List<Type>(
              new Type[] { typeof(DataTable) }
             )
            );
        }
    }
}


James

James Johnson

My views and opinions on running a .NET User Group, web development, evangelizing, mentoring, utilizing the latest technologies, living as a gringo in a Latin family, and, of course, life in general.

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