How to Sort a single Column in Asp.net Gridview

 <asp:gridview xmlns:asp="#unknown">
              ID="grdCause"
              runat="server
              EnableSortingAndPagingCallback="True"
              AllowPaging="True"
              AllowSorting="True"
              onpageindexchanging="grdCause_PageIndexChanging"
              onsorting="grdCause_Sorting"
         >
</asp:gridview>

private void LoadGrid()
    {
       
        DataSet ds = dal.ExecuteProcudere("CauseSelectAll", ht);
        grdCause.DataSource = ds.Tables[0];
        grdCause.DataBind();
    }
 
Gridview pageindexChanging Event  for paging:
protected void grdCause_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        grdCause.PageIndex = e.NewPageIndex;
        LoadGrid();
    }

 protected void grdCause_Sorting(object sender, GridViewSortEventArgs e)
    {
        string sortExpression = e.SortExpression;
 
        if (GridViewSortDirection == SortDirection.Ascending)
        {
            GridViewSortDirection = SortDirection.Descending;
            SortGridView(sortExpression, DESCENDING);
        }
        else
        {
            GridViewSortDirection = SortDirection.Ascending;
            SortGridView(sortExpression, ASCENDING);
        }
 

    }

private void SortGridView(string sortExpression, string direction)
    {
        //  You can cache the DataTable for improving performance
        LoadGrid();
        DataTable dt = grdCause.DataSource as DataTable;
        DataView dv = new DataView(dt);
        dv.Sort = sortExpression + direction;
 
        grdCause.DataSource = dv;
        grdCause.DataBind();
 
    }
    private const string ASCENDING = " ASC";
    private const string DESCENDING = " DESC";
 
    public SortDirection GridViewSortDirection
    {
        get
        {
            if (ViewState["sortDirection"] == null)
                ViewState["sortDirection"] = SortDirection.Ascending;
 
            return (SortDirection)ViewState["sortDirection"];
        }
        set { ViewState["sortDirection"] = value;
 }
    }

DataSet ds = ReportColumnBAL.GetGridDetails(Details);
            DataView dv = new DataView();
            dv.Table = ds.Tables[0];
            if (ViewState["SortExpr"] != null)
                dv.Sort = (string)ViewState["SortExpr"] + " " + (string)ViewState["SortDir"];
            gridview.DataSource = dv;
            gridview.DataBind();

protected void gridview_Sorting(object sender, GridViewSortEventArgs e)
        {
            ViewState["SortExpr"] = e.SortExpression;
            if (ViewState["SortDir"] != null)
                e.SortDirection = (string)ViewState["SortDir"] == "ASC" ? SortDirection.Descending : SortDirection.Ascending;
            ViewState["SortDir"] = e.SortDirection == SortDirection.Ascending ? "ASC" : "DESC";
            // call for function that binds grid again after sorting.
        }

OnSorting="gridview_Sorting"

<asp:TemplateField AccessibleHeaderText="Login Time"
                                        HeaderText="Login Time" SortExpression="logintime">
                                        
                                        <ItemTemplate>
                                            <asp:Label ID="Label1" runat="server" Text='<%#Bind("logintime")%>'></asp:Label>
                                        </ItemTemplate>

</asp:TemplateField>