Convert DataTable To JSON String in ASP.Net

First of all you need to create an "ASP.NET Empty Web Site". Then use the following procedure.

Step 1

Create a ConvertDataTableToJson class in the App_Code folder and provide the following:

Convert DataTable To JSON String.

using System.Data
using System.Text;
public class ConvertDatatableToJson
{
   public string DataTableToJson(DataTable dt)
   {
      DataSet ds = new DataSet();
      ds.Merge(dt);
      StringBuilder JsonStr = new StringBuilder();
      if (ds != null && ds.Tables[0].Rows.Count > 0)
      {
         JsonStr.Append("[");
         for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
         {
            JsonStr.Append("{");
            for (int j = 0; j < ds.Tables[0].Columns.Count; j++)
            {
               if (j < ds.Tables[0].Columns.Count - 1)
               {
                  JsonStr.Append("\"" + ds.Tables[0].Columns[j].ColumnName.ToString() + "\":" + "\"" + ds.Tables[0].Rows[i][j].ToString() + "\",");
               }
               else if (j == ds.Tables[0].Columns.Count - 1)
               {
                  JsonStr.Append("\"" + ds.Tables[0].Columns[j].ColumnName.ToString() + "\":" + "\"" + ds.Tables[0].Rows[i][j].ToString() + "\"");
               }
            }
            if (i == ds.Tables[0].Rows.Count - 1)
            {
               JsonStr.Append("}");
            }
            else
            {
               JsonStr.Append("},");
            }
         }
         JsonStr.Append("]");
         return JsonStr.ToString();
      }
      else
      {
         return null;
      }
   }

Step 2

Insert the grid view control into the Default.aspx page then write the following design code:

<asp:GridView ID="ui_grdVw_EmployeeDetail" runat="server" Width="50%" AutoGenerateColumns="false" HeaderStyle-CssClass="pageheading">
<Columns>
<asp:TemplateField HeaderText="S.NO">
<ItemTemplate>
<%#Container.DataItemIndex+1 %>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Employee ID">
<ItemTemplate>
<asp:Label ID="ui_lbl_EmployeeID" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Emp_id") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Employee Name">
<ItemTemplate>
<asp:Label ID="ui_lbl_EmployeeName" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Emp_Name") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Employee Post">
<ItemTemplate>
<asp:Label ID="ui_lbl_EmpJob" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Emp_job") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Department">
<ItemTemplate>
<asp:Label ID="ui_lbl_Department" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "Emp_Dep") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<br />
<asp:Button ID="ui_btn_Convert1" runat="server" Text="Manually Convert To Json" OnClick="ui_btn_Convert1_Click" /><br /><br /><br />
<asp:Label ID="ui_lbl_JsonString1" runat="server"></asp:Label>

Step 3

Now, open the Deafult.asps.cs then write the following code:

using System;
using System.Data;

public partial class _Default : System.Web.UI.Page
{
   #region Global Variable
   DataTable dt;
   ConvertDatatableToJson dtJ;
   string JsonString = string.Empty;
   #endregion

   protected void Page_Load(object sender, EventArgs e)
   {
      if (!IsPostBack)
      {
         ui_grdvw_EmployeeDetail_Bind();
      }
   }

   protected void ui_grdvw_EmployeeDetail_Bind()
   {
      dt = new DataTable();
      EmployeeRecord employeeRecord = new EmployeeRecord();
      dt = employeeRecord.EmpRecord();
      ViewState["dt"] = dt;
      ui_grdVw_EmployeeDetail.DataSource = dt;
      ui_grdVw_EmployeeDetail.DataBind();
   }

   protected void ui_btn_Convert1_Click(object sender, EventArgs e)
   {
      dtJ = new ConvertDatatableToJson();
      JsonString = dtJ.DataTableToJson((DataTable)ViewState["dt"]);
      ui_lbl_JsonString1.Text = JsonString;
   }
}

Step 4

Press F5, run the project.

Now, convert the DataTable to a JSON string using the newtonsoft DLL.

Step 1

Download the Newtonsoft DLL and move it to the ASP.Net project's bin folder.

Step 2

 

Then, insert a button and label UI Control in the Deafult.aspx page as in the following:

<asp:Button ID="iu_btn_Convert2" runat="server" Text="Newtonsoft Convert To Json" OnClick="iu_btn_Convert2_Click" />
<br />
<br />
<asp:Label ID="ui_lbl_JsonString2" runat="server"></asp:Label>

Step 3

 

Now, write the following code in Default.aspx.cs:

using this namespace.

using Newtonsoft.Json;

And then:

protected void iu_btn_Convert2_Click(object sender, EventArgs e)
{
   dt = (DataTable)ViewState["dt"];
   JsonString = JsonConvert.SerializeObject((DataTable)ViewState["dt"]);
   ui_lbl_JsonString2.Text = JsonString;
}

Now, run the project and click on the Newtonsoft Convert to JSON.

In the preceding code, I convert the DataTable to a JSON String.

I have attached the sample project for this, download and see how it works.

Thank you.