Partial Postback not working for ASP.Net GridView inside Update Panel

Make sure the following

1. GridView is inside UpdatePanel

2. There are no triggers

3. There are no JavaScript Errors on page

i verified all these

1. GridView is inside UpdatePanel

2. There are no triggers

3. There are no JavaScript Errors on page

there is partial page post back when updating.

but complete postback occuers when ADD button is clicked.

this is the html code

<%@ Page Title="" Language="C#" MasterPageFile="~/control/Control_MasterPage.master" AutoEventWireup="true" CodeFile="Materials_Required_Entry.aspx.cs" Inherits="control_Materials_Required_Entry" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>

<div id="container_kfh">

<div class="width-1050 center-margin">
<div id="grd12">


    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
<asp:GridView ID="grdMatReq" runat="server" AutoGenerateColumns="False" 
        ShowFooter="True" Font-Size="Small"
        AllowPaging ="True" onrowediting="EditMatReq" 
        OnPageIndexChanging = "OnPaging" CssClass="width-1050 center-margin center-text"
        onrowupdating="UpdateMatReq"  onrowcancelingedit="CancelEdit" 
        onrowdatabound="grdMatReq_RowDataBound" CellPadding="4" ForeColor="#333333" 
        GridLines="None" >
          <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
          <Columns>
        <asp:TemplateField  ItemStyle-Width = "0px" Visible="false" >
            <ItemTemplate>
              <asp:Label ID="lblsno" Visible="false" runat="server" Text='<%# Eval("sno")%>'></asp:Label>
            </ItemTemplate> 
            <FooterTemplate>
               
            </FooterTemplate> 

<ItemStyle Width="0px"></ItemStyle>
        </asp:TemplateField>
        <asp:TemplateField   HeaderText = "work order no">
        <headertemplate>
     work order no<br />رقم الأمر
    </headertemplate>

            <ItemTemplate>
                <asp:Label ID="lblwork_order_no" runat="server" Text='<%# Eval("work_order_no")%>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="txtEditwork_order_no"  runat="server" Text='<%# Eval("work_order_no")%>'></asp:TextBox>
            </EditItemTemplate>  
            <FooterTemplate>
               
            </FooterTemplate> 
        </asp:TemplateField>
        <asp:TemplateField   HeaderText = "material_req">
         <headertemplate>
     material_req<br />المواد المطلوبة
    </headertemplate>
            <ItemTemplate>
                <asp:Label ID="lblmaterial_req" runat="server" Visible="false" Text='<%# Eval("material_req")%>'></asp:Label>
                 <asp:DropDownList ID="dd_type" runat="server" ></asp:DropDownList>
            </ItemTemplate>
            <EditItemTemplate>  

               <asp:Label ID="lblmaterial_req" runat="server" Visible="false" Text='<%# Eval("material_req")%>'></asp:Label>
                <asp:DropDownList ID="dd_type" runat="server" ></asp:DropDownList>
            </EditItemTemplate>  
            <FooterTemplate>
                <asp:DropDownList ID="dd_type" runat="server" ></asp:DropDownList>
            </FooterTemplate> 
        </asp:TemplateField>



         <asp:TemplateField   HeaderText = "Quantity">
         <headertemplate>
     Quantity<br /> الكمية
    </headertemplate>
            <ItemTemplate>
                <asp:Label ID="lblqty" runat="server" Text='<%# Eval("qty")%>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
               
               <asp:TextBox ID="txtEditqty"  runat="server" Text='<%# Eval("qty")%>'></asp:TextBox>
               <asp:RequiredFieldValidator ID="RFV_txtEditqty" runat="server" 
                    ControlToValidate="txtEditqty" Display="Dynamic" ErrorMessage="Compulosry" SetFocusOnError="true" ValidationGroup="b"
                                             Text="*"></asp:RequiredFieldValidator>
            </EditItemTemplate>  
            <FooterTemplate>
                <asp:TextBox ID="txtInsertqty"  runat="server"></asp:TextBox>
                
                <asp:RequiredFieldValidator ID="RFV_txtInsertqty" runat="server"  
                    ControlToValidate="txtInsertqty" Display="Dynamic" ErrorMessage="Compulosry" ValidationGroup="a" 
                    SetFocusOnError="True" Text="*"></asp:RequiredFieldValidator>
                
            </FooterTemplate> 
        </asp:TemplateField>


        <asp:TemplateField   HeaderText = "unit_of_issue">
        <headertemplate>
     Unit Of Issue<br />وحدة الصرف
    </headertemplate>
            <ItemTemplate>
                <asp:Label ID="lblunit_of_issue" runat="server" Text='<%# Eval("unit_of_issue")%>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="txtEditunit_of_issue"  runat="server" Text='<%# Eval("unit_of_issue")%>'></asp:TextBox>
            </EditItemTemplate>  
            <FooterTemplate>
                <asp:TextBox ID="txtunit_of_issue"  runat="server"></asp:TextBox>
            </FooterTemplate> 
        </asp:TemplateField>

        <asp:TemplateField   HeaderText = "variance_type">
        <headertemplate>
     Variance Type<br />الاختلافـــــــات النوع
    </headertemplate>
            <ItemTemplate>
                <asp:Label ID="lblvariance_type" runat="server" Text='<%# Eval("variance_type")%>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="txtEditvariance_type"  runat="server" Text='<%# Eval("variance_type")%>'></asp:TextBox>
            </EditItemTemplate>  
            <FooterTemplate>
                <asp:TextBox ID="txtvariance_type"  runat="server"></asp:TextBox>
            </FooterTemplate> 
        </asp:TemplateField>

        <asp:TemplateField   HeaderText = "variance_quantity">
        <headertemplate>
     Variance Quantity<br />الاختلافـــــــات الكمية
    </headertemplate>
            <ItemTemplate>
                <asp:Label ID="lblvariance_quantity" runat="server" Text='<%# Eval("variance_quantity")%>'></asp:Label>
            </ItemTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="txtEditvariance_quantity"  runat="server" Text='<%# Eval("variance_quantity")%>'></asp:TextBox>
            </EditItemTemplate>  
            <FooterTemplate>
                <asp:TextBox ID="txtvariance_quantity"  runat="server"></asp:TextBox>
            </FooterTemplate> 
        </asp:TemplateField>
     
        <asp:TemplateField ItemStyle-Width = "30px" >
            <ItemTemplate>
                <asp:LinkButton ID="lnkRemove" runat="server" CommandArgument = '<%# Eval("sno")%>' 
                 OnClientClick = "return confirm('Do you want to delete?')"
                 OnClick = "DeleteProduct"><img alt="Delete" src="" /></asp:LinkButton>
            </ItemTemplate>
             <FooterTemplate>
             <asp:Button ID="btnAdd" runat="server" Text="Add" causesvalidation="true"
      validationgroup="a"  CssClass="art-button" OnClick = "AddNewMaterial" />
            </FooterTemplate> 

<ItemStyle Width="30px"></ItemStyle>
        </asp:TemplateField> 
        <asp:CommandField ItemStyle-Width="30" ButtonType="Link"    ShowEditButton="True" 
                  ValidationGroup="b" > 
<ItemStyle Width="30px"></ItemStyle>
              </asp:CommandField>
       </Columns> 
                                          <EditRowStyle BackColor="#999999" />
          <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
          <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
          <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
          <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
          <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
          <SortedAscendingCellStyle BackColor="#E9E7E2" />
          <SortedAscendingHeaderStyle BackColor="#506C8C" />
          <SortedDescendingCellStyle BackColor="#FFFDF8" />
          <SortedDescendingHeaderStyle BackColor="#6F8DAE" />
                                          </asp:GridView>
                                          </ContentTemplate>
                                         
                                       
                                         
                                          </asp:UpdatePanel>
</div>
</div>
<div class="lbl_wrap">
    <asp:LinkButton ID="LinkButton1" runat="server" 
        PostBackUrl="~/control/WorkOrders.aspx">Back To Work Orders</asp:LinkButton>
    <asp:Label ID="lblMessage" runat="server" Text=""></asp:Label>
   
   
  
    
</div>
</div>
</asp:Content>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using BusinessObject;
using ExceptionalLogger;
using KFHDal;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Data;
using System.IO;
using System.Configuration;
using System.Web.Security;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class control_Materials_Required_Entry : System.Web.UI.Page
{
    Material_Required objMatReq = new Material_Required();
    Material_RequiredDAL objMatReqDal = new Material_RequiredDAL();
    protected void Page_Load(object sender, EventArgs e)
    {
        //Label1.Text = Request.QueryString["name"];
        if (!Page.IsPostBack)
        {
            GetData();
        }
    }
    #region Methods

    public void GetException(string strErrorMessage)
    {
        if (!Directory.Exists(("ErrorLog")))
        {
            Directory.CreateDirectory(Server.MapPath("ErrorLog"));
        }
        string strpath = Request.PhysicalApplicationPath + @"\ErrorLog\ErrorLog_" + DateTime.Now.ToString("ddMMyy") + ".txt";
        CommonUtility.ErrorLog(strpath, strErrorMessage);
    }
    public void GetData()
    {
        try
        {
            DataSet MatReqds = CommonMethods.GetDataByID("Materials_Required_Tbl","work_order_no",Request.QueryString["workorderno"].ToString());

            //if (MatReqds.Tables[0].Rows.Count > 0)
            //{
                grdMatReq.DataSource = MatReqds;
                grdMatReq.DataBind();

                // to fixthe grid if no data found ..
                EmptyGridFix(grdMatReq);
            //}
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }
    }

    protected void EmptyGridFix(GridView grdView)
    {
        // normally executes after a grid load method
        if (grdView.Rows.Count == 0 &&
            grdView.DataSource != null)
        {
            DataTable dt = null;

            // need to clone sources otherwise
            // it will be indirectly adding to 
            // the original source

            if (grdView.DataSource is DataSet)
            {
                dt = ((DataSet)grdView.DataSource).Tables[0].Clone();
            }
            else if (grdView.DataSource is DataTable)
            {
                dt = ((DataTable)grdView.DataSource).Clone();
            }

            if (dt == null)
            {
                return;
            }

            dt.Rows.Add(dt.NewRow()); // add empty row
            grdView.DataSource = dt;
            grdView.DataBind();

            // hide row
            grdView.Rows[0].Visible = false;
            grdView.Rows[0].Controls.Clear();
        }

        // normally executes at all postbacks
        if (grdView.Rows.Count == 1 &&
            grdView.DataSource == null)
        {
            bool bIsGridEmpty = true;

            // check first row that all cells empty
            for (int i = 0; i < grdView.Rows[0].Cells.Count; i++)
            {
                if (grdView.Rows[0].Cells[i].Text != string.Empty)
                {
                    bIsGridEmpty = false;
                }
            }
            // hide row
            if (bIsGridEmpty)
            {
                grdView.Rows[0].Visible = false;
                grdView.Rows[0].Controls.Clear();
            }
        }
    }

    #endregion
    protected void DeleteProduct(object sender, EventArgs e)
    {
        LinkButton lnkRemove = (LinkButton)sender;

        int intResult = CommonMethods.DeleteData("Materials_Required_Tbl", "sno", lnkRemove.CommandArgument.ToString());
        if (intResult == 0)
        {
            lblMessage.Text = "Record has been Deleted Successfully";
        }
        GetData();

    }
    protected void OnPaging(object sender, GridViewPageEventArgs e)
    {
        GetData();
        grdMatReq.PageIndex = e.NewPageIndex;
        grdMatReq.DataBind();
    }

    protected void AddNewMaterial(object sender, EventArgs e)
    {
        DropDownList dd_type = (DropDownList)grdMatReq.FooterRow.FindControl("dd_type");
       //string wo = ((TextBox)grdMatReq.FooterRow.FindControl("txtwork_order_no")).Text;
       // string material_req = ((TextBox)grdMatReq.FooterRow.FindControl("txtmaterial_req")).Text;
        string ui = ((TextBox)grdMatReq.FooterRow.FindControl("txtunit_of_issue")).Text;
        string vt = ((TextBox)grdMatReq.FooterRow.FindControl("txtvariance_type")).Text;
        string vq = ((TextBox)grdMatReq.FooterRow.FindControl("txtvariance_quantity")).Text;
        string q = ((TextBox)grdMatReq.FooterRow.FindControl("txtInsertqty")).Text;
        objMatReq.work_order_no = Convert.ToInt32(Request.QueryString["workorderno"].ToString());
            //Convert.ToInt32(wo.ToString());//Convert.ToInt32(Request.QueryString["workorderno"].ToString());

        objMatReq.material_req = (dd_type.SelectedValue.ToString());
        objMatReq.unit_of_issue = ui.ToString();
        objMatReq.variance_type = vt.ToString();
        objMatReq.variance_quantity = vq.ToString();
        objMatReq.qty = q.ToString();
        //  objProduct.Userid = Convert.ToInt32(ddClient.SelectedValue.ToString());
        int intResult = objMatReqDal.MatReqInsertUpdate(objMatReq);
        if (intResult == 50000)
        {
            lblMessage.Text = "Category Already Exist.";
        }
        else if (intResult == 50001)
        {
            lblMessage.Text = "Insert Successfully.";
        }
        else if (intResult == 50002)
        {
            lblMessage.Text = "Updated Successfully.";
        }

        GetData();
        Response.Redirect(Request.Url.AbsoluteUri);
    }
    protected void EditMatReq(object sender, GridViewEditEventArgs e)
    {
        grdMatReq.EditIndex = e.NewEditIndex;
        GetData();

    }
    protected void CancelEdit(object sender, GridViewCancelEditEventArgs e)
    {
        grdMatReq.EditIndex = -1;
        GetData();
    }
    protected void UpdateMatReq(object sender, GridViewUpdateEventArgs e)
    {

        DropDownList dd_type = (DropDownList)grdMatReq.Rows[e.RowIndex].FindControl("dd_type");
        string sno = ((Label)grdMatReq.Rows[e.RowIndex].FindControl("lblsno")).Text;
        
        //string material_req = ((TextBox)grdMatReq.Rows[e.RowIndex].FindControl("txtEditmaterial_req")).Text;
        string ui = ((TextBox)grdMatReq.Rows[e.RowIndex].FindControl("txtEditunit_of_issue")).Text;
        string vt = ((TextBox)grdMatReq.Rows[e.RowIndex].FindControl("txtEditvariance_type")).Text;
        string vq = ((TextBox)grdMatReq.Rows[e.RowIndex].FindControl("txtEditvariance_quantity")).Text;
        string q = ((TextBox)grdMatReq.Rows[e.RowIndex].FindControl("txtEditqty")).Text;
        //DropDownList dd_type = (DropDownList)grdMatReq.Rows[e.RowIndex].FindControl("dd_type");
        //  string UserID = ((DropDownList)GridView1.Rows[e.RowIndex].FindControl("ddCustProd")).SelectedItem.Value;
        objMatReq.sno = Convert.ToInt32(sno.ToString());
        objMatReq.material_req = dd_type.SelectedItem.ToString();
        objMatReq.unit_of_issue = ui.ToString();
        objMatReq.variance_type = vt.ToString();
        objMatReq.variance_quantity = vq.ToString();
        objMatReq.qty = q.ToString();
        objMatReq.work_order_no = Convert.ToInt32(Request.QueryString["workorderno"].ToString());

        int intResult = objMatReqDal.MatReqInsertUpdate(objMatReq);

        if (intResult == 50000)
        {
            lblMessage.Text = " Already Exist.";
        }
        if (intResult == 50001)
        {
            lblMessage.Text = "Insert Successfully.";
        }
        if (intResult == 50002)
        {
            lblMessage.Text = "Updated Successfully.";
            GetData();
        }

        if(intResult == 50003)
        {
            lblMessage.Text = "Deleted Successfully.";
            GetData();
        }
        grdMatReq.EditIndex = -1;
        GetData();

    }


    protected void grdMatReq_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            DropDownList ddtype = (DropDownList)e.Row.FindControl("dd_type");
            Label lblmaterial_req = (Label)e.Row.FindControl("lblmaterial_req");

            DataSet dsclient = CommonMethods.GetDataByID("category_tbl", "cat_type_id", "3");
            if (dsclient.Tables[0].Rows.Count > 0)
            {
                ddtype.DataSource = dsclient;
                ddtype.DataTextField = "cat_type";
                ddtype.DataValueField = "cat_type";
                ddtype.DataBind();
                ddtype.Items.Insert(0, new ListItem("- Select -", "0"));
                if (lblmaterial_req.Text.Trim() == "0")
                {
                    ddtype.SelectedValue = "0";
                }
                else
                {
                    ddtype.SelectedValue = lblmaterial_req.Text.ToString();
                }
            }
        }
        if (e.Row.RowType == DataControlRowType.Footer)
        {
            DropDownList ddtype = (DropDownList)e.Row.FindControl("dd_type");


            DataSet dsclient = CommonMethods.GetDataByID("category_tbl", "cat_type_id", "3");
            if (dsclient.Tables[0].Rows.Count > 0)
            {
                ddtype.DataSource = dsclient;
                ddtype.DataTextField = "cat_type";
                ddtype.DataValueField = "cat_type";
                ddtype.DataBind();
                ddtype.Items.Insert(0, new ListItem("- Select -", "0"));
            }
        }
    }
  
  
}

There is no reason why your Add button is doing full postback since if any control is inside update panel it will do partial postback unless specified in trigger as PostBackTrigger.

Try adding another button in FooterTemplate with different Id and also you can download code from my article

GridView - Add Edit Update Delete and Paging the ajax way

and compare with yours