How to pass GridView SortExpression to GridViewPageIndexChanging Event in ASP.Net

Hi Amol111,

Can you explain in more detail what exactly you are trying to acheive if possible explain it with example?

I am trying to maintain sorting expression values while paging event of Grid.

But it takes null value in Viewstate ["Sort Expression"].ToString(); it throws  object value not set to an a instance of object exception.

private DataView Getdata()
        {
            using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString()))
            {
                DataSet dsEmployee = new DataSet();
                string strSelectCmd = "SELECT [Emp_Name],[Emp_id],[Emp_job],[Emp_Dep],[Emp_Salary] FROM [employee]";
                SqlDataAdapter da = new SqlDataAdapter(strSelectCmd, conn);
                da.Fill(dsEmployee, "Employee");
                DataView dvEmp = dsEmployee.Tables["Employee"].DefaultView;
                dvEmp.Sort = ViewState["SortExpr"].ToString();
                return dvEmp;    
            }
        }

Hi Amol111,

I have created a sample which full fill your requirement

HTML

<div>
    <asp:GridView ID="GridView1" runat="server" AllowSorting="true" AllowPaging="true"
        PageSize="10" OnSorting="GridView1_Sorting" OnPageIndexChanging="GridView1_PageIndexChanging">
    </asp:GridView>
</div>

C#

public string sortDirection
{
    get
    {
        return ViewState["sortDirection"] == null ? "ASC" : ViewState["sortDirection"].ToString();
    }
    set
    {
        ViewState["sortDirection"] = value;
    }
}

public string sortExpression
{
    get
    {
        return ViewState["SortExpression"] == null ? "CustomerID" : ViewState["SortExpression"].ToString();
    }
    set
    {
        ViewState["SortExpression"] = value;
    }
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        GridView1.DataSource = BindData();
        GridView1.DataBind();
    }
}

private DataTable BindData()
{
    string strConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
    DataTable dt = new DataTable();
    using (SqlConnection con = new SqlConnection(strConnString))
    {
        string strQuery = "SELECT TOP 20 CustomerID,ContactName,City FROM Customers";
        SqlCommand cmd = new SqlCommand(strQuery);
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            con.Open();
            sda.SelectCommand = cmd;
            sda.Fill(dt);
            return dt;
        }
    }
}

protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
    if (sortDirection == e.SortDirection.ToString())
    {
        sortDirection = "Descending";
        sortExpression = e.SortExpression.ToString();
        SortGridView(sortExpression, sortDirection.ToString());
    }
    else
    {
        sortDirection = "Ascending";
        sortExpression = e.SortExpression.ToString();
        SortGridView(sortExpression, sortDirection.ToString());
    }
}

private void SortGridView(string sortExpression, string direction)
{
    //  You can cache the DataTable for improving performance
    DataView dv = new DataView(BindData());
    if (sortDirection == "Ascending")
    {
        dv.Sort = sortExpression + " " + "ASC";
    }
    else
    {
        dv.Sort = sortExpression + " " + "DESC";
    }
    GridView1.DataSource = dv;
    GridView1.DataBind();
}

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView1.PageIndex = e.NewPageIndex;
    SortGridView(sortExpression, sortDirection);
}

ScreenShot