Golden Code: Maintain Sorting While Moving to Next Page In Data Grid

default.aspx:


       < asp : datagrid id="grd" runat="server" allowpaging="true" pagesize="4" allowsorting="true" autogeneratecolumns="false" onpageindexchanged="grd_PageIndexChanged" onsortcommand="grd_SortCommand">
       < columns >
           < asp : boundcolumn headertext="ID" datafield="ID" sortexpression="ID" />
           < asp : boundcolumn headertext="Name" datafield="Name" sortexpression="Name" />
           < asp : boundcolumn headertext="Marks" datafield="Marks" sortexpression="Marks" />
       < / columns >  
       < pagerstyle horizontalalign="Center" mode="NextPrev" />
       
   
   




default.aspx.cs: (Code behind file)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

namespace Data_Controls
{
   public partial class _Default : System.Web.UI.Page
   {
       protected void Page_Load(object sender, EventArgs e)
       {
           FillGrid();

           if (!Page.IsPostBack)
           {
               FillColumnsSortDirectionList();  
           }

           SetPagingSorting();
       }

       private void FillGrid()
       {
           DataView view = LoadView();

           this.grd.DataSource = view;
           this.grd.DataBind();
       }

       private void FillColumnsSortDirectionList()
       {
           DataView view = (DataView)this.grd.DataSource;
           List ColumnsSortDirectionList = new List();
         
           foreach (DataColumn column in view.ToTable().Columns)
               ColumnsSortDirectionList.Add(new Pair(column.ColumnName, "asc"));

           Session.Add("ColumnsSortDirectionList", ColumnsSortDirectionList);

           Session.Add("SortColumn", "ID");
       }

       private void SetPagingSorting()
       {
           ((DataView)this.grd.DataSource).Sort = Session["SortColumn"].ToString() + " " +
               Utility.PairList__GetValue((List)Session["ColumnsSortDirectionList"], Session["SortColumn"].ToString());
       }

       private DataTable LoadTable()
       {
           DataTable tab = new DataTable();
           tab.Columns.Add("ID", typeof(int));
           tab.Columns.Add("Name", typeof(string));
           tab.Columns.Add("Marks", typeof(double));

           tab.Rows.Add(new object[] { 1, "Atif", 85.40d });
           tab.Rows.Add(new object[] { 2, "Jamal", 70.00d });
           tab.Rows.Add(new object[] { 3, "Nawaz", 60.00d });
           tab.Rows.Add(new object[] { 4, "Salma", 75.00d });
           tab.Rows.Add(new object[] { 5, "Yasir", 78.00d });
           tab.Rows.Add(new object[] { 6, "Shabnam", 50.00d });
           tab.Rows.Add(new object[] { 7, "Naseem", 74.32d });
           tab.Rows.Add(new object[] { 8, "Tauseef", 58.00d });
           tab.Rows.Add(new object[] { 9, "Nasreen", 18.00d });
           tab.Rows.Add(new object[] { 10, "Sadiq", 90.00d });

           return tab;
       }

       private DataView LoadView()
       {
           return LoadTable().DefaultView;
       }

       protected void grd_PageIndexChanged(object source, DataGridPageChangedEventArgs e)
       {
           this.grd.CurrentPageIndex = e.NewPageIndex;
           this.grd.DataBind();
       }

       protected void grd_SortCommand(object source, DataGridSortCommandEventArgs e)
       {
           Session["SortColumn"] = e.SortExpression;

           ColumnsSortDirectionList__ToggleValue(e.SortExpression);

           ((DataView)this.grd.DataSource).Sort = e.SortExpression + " " +
               Utility.PairList__GetValue((List)Session["ColumnsSortDirectionList"], e.SortExpression);
           this.grd.DataBind();
       }

       private void ColumnsSortDirectionList__ToggleValue(string _Name)
       {
           List ColumnsSortDirectionList = (List)Session["ColumnsSortDirectionList"];

           foreach (Pair p in ColumnsSortDirectionList)
           {
               if (p.Name == _Name)
               {
                   if (p.Value == "asc")
                       p.Value = "desc";
                   else if (p.Value == "desc")
                       p.Value = "asc";

                   break;
               }
           }
       }
     
   }
}

Pair.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Data_Controls
{
   public class Pair
   {
       public string Name;
       public string Value;

       public Pair(string _Name, string _Value)
       {
           this.Name = _Name;
           this.Value = _Value;
       }
   }
}

Utility.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Data_Controls
{
   public class Utility
   {
       public static string PairList__GetName(List _PairList, string _Value)
       {
           string returnValue = "";

           foreach (Pair p in _PairList)
           {
               if (p.Value == _Value)
               {
                   returnValue = p.Name;
                   break;
               }
           }

           return returnValue;
       }

       public static string PairList__GetValue(List _PairList, string _Name)
       {
           string returnValue = "";

           foreach (Pair p in _PairList)
           {
               if (p.Name == _Name)
               {
                   returnValue = p.Value;
                   break;
               }
           }

           return returnValue;
       }
   }
}