GridView lost sorting after paging? - asp.net

Question

I got the below code from internet. It is working properly. I have added paging also. When I'm just sorting, it is working properly. When I am changing the page index, the sorting is lost.
Here is the client side code that set a gridview with 20 items per page, using the sort linked to the "GridView1_Sorting" method in the server side code.
Client side
<asp:GridView ID="GridView1" runat="server" DataKeyNames="eno" AutoGenerateColumns="False" PageSize="20" AllowPaging="True" AllowSorting="True" OnSorting="GridView1_Sorting" CellPadding="4">
<Columns>
<asp:TemplateField HeaderText="Employee no" SortExpression="eno">
<ItemTemplate>
<%#Eval("eno")%>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Emp name" SortExpression="empname">
<ItemTemplate>
<%#Eval("empname")%>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Salary" SortExpression="sal">
<ItemTemplate>
<%#Eval("sal")%>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
And now the server side code:
Server side
using System.Data.SqlClient;
using System.Configuration;
using System.IO;
public partial class _Default : System.Web.UI.Page
{
SqlConnection sqlcon = new SqlConnection(ConfigurationManager.ConnectionStrings["Con"].ConnectionString);
SqlCommand sqlcmd;
SqlDataAdapter da;
DataTable dt = new DataTable();
DataTable dt1 = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
GridData();
}
}
void GridData()
{
sqlcmd = new SqlCommand("select * from emp", sqlcon);
sqlcon.Open();
da = new SqlDataAdapter(sqlcmd);
dt.Clear();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
Session["dt"] = dt;
GridView1.DataSource = dt;
GridView1.DataBind();
}
}
private string GVSortDirection
{
get { return ViewState["SortDirection"] as string ?? "DESC"; }
set { ViewState["SortDirection"] = value; }
}
private string GetSortDirection()
{
switch (GVSortDirection)
{
case "ASC":
GVSortDirection = "DESC";
break;
//assign new direction as ascending order
case "DESC":
GVSortDirection = "ASC";
break;
}
return GVSortDirection;
}
protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
DataTable dataTable = (DataTable)Session["dt"];
if (dataTable != null)
{
DataView dataView = new DataView(dataTable);
string sortDirection = GetSortDirection();
dataView.Sort = e.SortExpression + " " + sortDirection;
GridView1.DataSource = dataView;
GridView1.DataBind();
}
}
protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
GridView1.PageIndex = e.NewPageIndex;
GridData();
}
}

Answer 1

When you page, the PageIndexChanging event is called. This in turn runs the GridData() procedure, which sets the data source for the gridview to be a data table containing records from the emp table, with no particular sort order.
What you should do is to take the code that you've written in your GridView1_Sorting event-handler, and include this within the GridData routine, so that whenever the grid is populated with data - whether when the page first loads, when the page index is changed or when the gridview is sorted - the gridview is based on a sorted dataview, rather than an unsorted data table.

Answer 2

The way you are maintaining SortDirection using GetSortDirection, in same fashion maintain SortExpression.
Happy coding!!!

Answer 3

Have a look to this article, may you will get what you want