Filter ASP.Net GridView with TextBox in header Error: Cannot find column ASC

Is there an example of filter gridview with textbox for specifics column doing filter and sort using sql data? 

I was looking at the following, but i was not able to figure out how to use SQL data here

Filter GridView based on GridView Header TextBox with Paging and Sorting without using Stored Procedure in ASP.Net

Error: Sys.WebForms.PageRequestManagerServerErrorException: Cannot find column ASC

            <asp:UpdatePanel runat="server">
                <ContentTemplate>
                    <br />
                    <asp:HiddenField ID="hfClassApplied" runat="server" />
                    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="ID"
                        BackColor="White" BorderColor="#999999" BorderStyle="Solid" CellPadding="5" ForeColor="Black"
                        GridLines="Both" AllowPaging="False" CellSpacing="1" EmptyDataText="No outstanding orders found"
                        OnRowDataBound="GridView1_RowDataBound" >
                        <FooterStyle BackColor="#CCCCCC" />
                        <Columns>
                            <asp:BoundField DataField="ID" HeaderText="ID"/>
                            <asp:BoundField DataField="DEPT" HeaderText="DEPT"/>
                            <asp:TemplateField>
                                <HeaderTemplate>
                                    <asp:Label ID="lblJobno" Text="Job No" runat="server" />
                                    <asp:TextBox ID="txtJobno" runat="server" AutoPostBack="true" OnTextChanged="TextChanged" />
                                    <asp:LinkButton ID="lnkJobno" runat="server" OnClick="Sort" CssClass="glyphicon glyphicon-arrow-up"></asp:LinkButton>
                                </HeaderTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="Label2" Text='<%# Eval("[Job No]") %>' runat="server" />
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="Tracking" HeaderText="Tracking" />
                            <asp:BoundField DataField="ItemNum" HeaderText="ItemNum" />
                        </Columns>
                        <PagerStyle HorizontalAlign="Center" CssClass="pgr" />
                        <SelectedRowStyle BackColor="#000099" Font-Bold="True" ForeColor="White" />
                    </asp:GridView>
                    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>" SelectCommand="SELECT * FROM [PerTab]"></asp:SqlDataSource>
                </ContentTemplate>
            </asp:UpdatePanel>

        public string GetCon()
        {
            return ConfigurationManager.ConnectionStrings["hr"].ConnectionString;
        }
 
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindGrid();
            }
 
        }
 
        public string sortDirection
        {
            get
            {
                return ViewState["sortDirection"] == null ? "ASC" : ViewState["sortDirection"].ToString(); // your default sort direction i.e. ASC.
            }
            set
            {
                ViewState["sortDirection"] = value;
            }
        }
 
        public string sortExpression
        {
            get
            {
                return ViewState["SortExpression"] == null ? "[Job No]" : ViewState["SortExpression"].ToString(); //Your by default sort expression. i.e. ColumnName
            }
            set
            {
                ViewState["SortExpression"] = value;
            }
        }
 
        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.Header)
            {
                LinkButton lnkJobno = e.Row.FindControl("lnkJobno") as LinkButton;
                Label lblJobno = e.Row.FindControl("lblJobno") as Label;
 
                if (!string.IsNullOrEmpty(hfClassApplied.Value))
                {
                    if (sortExpression == lblJobno.Text)
                    {
                        lnkJobno.CssClass = hfClassApplied.Value;
                    }
                }
            }
        }
 
        protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            GridView1.PageIndex = e.NewPageIndex;
            SortGridView(sortExpression);
        }
 
        public void BindGrid()
        {
            using (SqlConnection con = new SqlConnection(GetCon()))
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT * FROM [PerTab]";
                    cmd.Connection = con;
                    SqlDataAdapter sda = new SqlDataAdapter(cmd);
                    DataTable dt = new DataTable();
                    sda.Fill(dt);
                    if (ViewState["GridView"] == null)
                    {
                        ViewState["GridView"] = dt;
                    }
                    GridView1.DataSource = ViewState["GridView"] as DataTable;
                    GridView1.DataBind();
                }
            }
        }
 
        private void SortGridView(string sortExpression)
        {
            DataTable dt = new DataTable();
 
            if (ViewState["GridView"] != null)
            {
                dt = ViewState["GridView"] as DataTable;
            }
            DataView dv = new DataView(dt);
            if (sortDirection == "ASC")
            {
                dv.Sort = sortExpression + " " + "ASC";
            }
            else
            {
                dv.Sort = sortExpression + " " + "DESC";
            }
            GridView1.DataSource = dv;
            GridView1.DataBind();
        }
 
        protected void Sort(object sender, EventArgs e)
        {
            string assignedClass = (sender as LinkButton).CssClass.Split('-')[2];
            if (assignedClass.ToUpper() == "UP")
            {
                sortDirection = "ASC";
                hfClassApplied.Value = "glyphicon glyphicon-arrow-down";
            }
            else
            {
                sortDirection = "DESC";
                hfClassApplied.Value = "glyphicon glyphicon-arrow-up";
            }
            string selectedId = (sender as LinkButton).ID;
            Label lblJobno = (sender as LinkButton).FindControl("lblJobno") as Label;
            LinkButton lnkJobno = (sender as LinkButton).FindControl("lnkJobno") as LinkButton;
 
            if (lnkJobno.ID == selectedId)
            {
                sortExpression = lnkJobno.Text;
            }
 
            SortGridView(sortExpression);
        }