Sorting in gridview

 public SortDirection dir
    {
        get
        {
            if (ViewState["dirState"] == null)
            {
                ViewState["dirState"] = SortDirection.Ascending;
            }
            return (SortDirection)ViewState["dirState"];
        }
        set
        {
            ViewState["dirState"] = value;
        }
    }
    protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {
        all_resol();
        DataTable dt = new DataTable();
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());
        SqlCommand cmd = new SqlCommand("select* from Details whereActive='Active' and Status=1 ", con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        dt = ds.Tables[0];
        {
            string SortDir = string.Empty;
            if (dir == SortDirection.Ascending)
            {
                dir = SortDirection.Descending;
                SortDir = "Desc";
            }
            else
            {
                dir = SortDirection.Ascending;
                SortDir = "Asc";
            }
            DataView sortedView = new DataView(dt);
            sortedView.Sort = e.SortExpression + " " + SortDir;
            GridView1.DataSource = sortedView;
            GridView1.DataBind();
        }
    }


 <asp:TemplateField HeaderText="IS" SortExpression="IS">
</asp:TemplateField>