Select2 plugin inside Gridview works with only last row of grid in asp.net

HEADER used select2-4.0.13 and bootstrap v4.4.1 in asp.net webpage

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
    <link href="Styles/Bootstrap v4.4.1/bootstrap.min.css" rel="stylesheet" type="text/css" />
    <link href="Styles/Select2-4.0.13/select2.min.css" rel="stylesheet" type="text/css" />
    <link href="Styles/Select2-4.0.13/select2-bootstrap4.min.css" rel="stylesheet" type="text/css" />
</asp:Content>

ASPX Page created gridview with 3 columns where first column contains dropdownlist with select2 plug in, but select2 works with only last row for gridview, for other rows it displays normal dropdown list

<asp:GridView ID="grdPackingSlipItem" runat="server" AllowPaging="false" AutoGenerateColumns="False"
        CssClass="table-xs table-responsive table-striped table-bordered table-hover p-1"
        EmptyDataText="No rows for the selection criteria." EnableTheming="False" OnRowDataBound="grdPackingSlipItem_RowDataBound">
        <Columns>
            <asp:TemplateField HeaderText="Sl.No" HeaderStyle-HorizontalAlign="Left" ItemStyle-HorizontalAlign="Left" ItemStyle-Width="50" HeaderStyle-Font-Bold="false">
                <ItemTemplate>
                    <%# Container.DataItemIndex + 1 %>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Item Name" HeaderStyle-HorizontalAlign="Left" ItemStyle-HorizontalAlign="Left"
                ItemStyle-Width="220" HeaderStyle-Font-Bold="false" ControlStyle-Width="100%">
                <ItemTemplate>
                    <asp:DropDownList runat="server" ID="grdtxtItemName" ClientIDMode="Static" data-width="100%"
                        CssClass="select2-single input-sm w-100" data-placeholder="Item Name....." AppendDataBoundItems="true">
                    </asp:DropDownList>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Pcs" HeaderStyle-HorizontalAlign="Center" ItemStyle-HorizontalAlign="Center"
                ItemStyle-Width="100" HeaderStyle-Font-Bold="false" ControlStyle-Width="100%">
                <ItemTemplate>
                    <asp:TextBox ID="grdtxtPcs" runat="server" ClientIDMode="Static" onkeypress="return isIntegerKey(event);"
                        OnPaste="return false" MaxLength="10" BorderStyle="Solid" BorderColor="WhiteSmoke"
                        Text='<%#DataBinder.Eval(Container.DataItem, "QUANTITY")%>'>
                    </asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>        
        </Columns>
        <HeaderStyle Font-Names="Tahoma" Font-Size="9pt" BackColor="#5D7B9D" Font-Bold="false"
            ForeColor="White" HorizontalAlign="Center" />
        <RowStyle Font-Names="Tahoma" Font-Size="10pt" ForeColor="Black" Height="30" />
        <PagerStyle CssClass="GridPager" />
    </asp:GridView>

Script Section linked required scripts bootstrap4 and select2 scripts , initialised select2 for dropdownlist with ID “.select2-single”

<script src="Scripts/jquery-3.4.1/jquery-3.4.1.min.css" type="text/javascript"></script>
    <script src="Scripts/Bootstrap v4.4.1/popper.min.js" type="text/javascript"></script>
    <script src="Scripts/Bootstrap v4.4.1/bootstrap.min.js" type="text/javascript"></script>
    <script src="Scripts/Bootstrap v4.4.1/bootstrap.bundle.min.js" type="text/javascript"></script>
    <script src="Scripts/Select2-4.0.13/select2.full.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            initSelect2();
        });

        function pageLoad() {
            initSelect2();
        }

        function initSelect2() {
            $('.select2-single').select2({
                theme: 'bootstrap4',
                width: 'style',
                containerCssClass: ':all:',
                allowClear: true
            });
        }
    </script>

Code Behind

loaded gridview with datatable in page load

private void LoadGridData()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("RECORD_ID", typeof(int)));
            dt.Columns.Add(new DataColumn("PRODUCT_ID", typeof(int)));
            dt.Columns.Add(new DataColumn("PRODUCT_NAME", typeof(string)));
            dt.Columns.Add(new DataColumn("QUANTITY", typeof(int)));
            //empty row on if no record
            DataRow dtEmptyrow = dt.NewRow();
            dtEmptyrow["RECORD_ID"] = 1;
            dtEmptyrow["PRODUCT_ID"] = 1;
            dtEmptyrow["PRODUCT_NAME"] = "Apple";
            dtEmptyrow["QUANTITY"] = 100;
            dt.Rows.Add(dtEmptyrow);

            dtEmptyrow = dt.NewRow();
            dtEmptyrow["RECORD_ID"] = 2;
            dtEmptyrow["PRODUCT_ID"] = 5;
            dtEmptyrow["PRODUCT_NAME"] = "Oppo";
            dtEmptyrow["QUANTITY"] = 500;
            dt.Rows.Add(dtEmptyrow);

            dtEmptyrow = dt.NewRow();
            dtEmptyrow["RECORD_ID"] = 3;
            dtEmptyrow["PRODUCT_ID"] = 3;
            dtEmptyrow["PRODUCT_NAME"] = "Samsung";
            dtEmptyrow["QUANTITY"] = 300;
            dt.Rows.Add(dtEmptyrow);


            ViewState["PackingSlipItem"] = dt.Copy(); // original copy
            grdPackingSlipItem.DataSource = dt;
            grdPackingSlipItem.DataBind();
        }

on gridview row databound bind list of items for dropdown list

protected void grdPackingSlipItem_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            try
            {
                if (e.Row.RowType == DataControlRowType.DataRow)
                {
                    //onrowdatabound = true;
                    DataTable oDataTableSubCategory = new DataTable();
                    oDataTableSubCategory.Columns.Add(new DataColumn("PRODUCT_ID", typeof(int)));
                    oDataTableSubCategory.Columns.Add(new DataColumn("PRODUCT_NAME", typeof(string)));
                    
                    //empty row on if no record
                    DataRow dtEmptyrow = oDataTableSubCategory.NewRow();
                    dtEmptyrow["PRODUCT_ID"] = 1;
                    dtEmptyrow["PRODUCT_NAME"] ="Apple";
                    oDataTableSubCategory.Rows.Add(dtEmptyrow);

                    dtEmptyrow = oDataTableSubCategory.NewRow();
                    dtEmptyrow["PRODUCT_ID"] = 2;
                    dtEmptyrow["PRODUCT_NAME"] = "Microsoft";
                    oDataTableSubCategory.Rows.Add(dtEmptyrow);

                    dtEmptyrow = oDataTableSubCategory.NewRow();
                    dtEmptyrow["PRODUCT_ID"] = 3;
                    dtEmptyrow["PRODUCT_NAME"] = "Samsung";
                    oDataTableSubCategory.Rows.Add(dtEmptyrow);

                    dtEmptyrow = oDataTableSubCategory.NewRow();
                    dtEmptyrow["PRODUCT_ID"] = 4;
                    dtEmptyrow["PRODUCT_NAME"] = "Nokia";
                    oDataTableSubCategory.Rows.Add(dtEmptyrow);
                    
                    dtEmptyrow = oDataTableSubCategory.NewRow();
                    dtEmptyrow["PRODUCT_ID"] = 5;
                    dtEmptyrow["PRODUCT_NAME"] = "Oppo";
                    oDataTableSubCategory.Rows.Add(dtEmptyrow);
                    
                    DropDownList DropDownList1 = (e.Row.FindControl("grdtxtItemName") as DropDownList);
                    DropDownList1.Items.Clear();
                    DropDownList1.Items.Insert(0, new ListItem(String.Empty, String.Empty));
                    //DropDownList1.SelectedIndex = 0;
                    DropDownList1.DataSource = oDataTableSubCategory;
                    DropDownList1.DataTextField = "PRODUCT_NAME";
                    DropDownList1.DataValueField = "PRODUCT_ID";
                    DropDownList1.DataBind();
                    string selectedPRODUCTSUBCAT_ID = DataBinder.Eval(e.Row.DataItem, "PRODUCT_ID").ToString();
                    string selectedPRODUCTSUBCAT_NAME = DataBinder.Eval(e.Row.DataItem, "PRODUCT_NAME").ToString();
                    DropDownList1.Items.FindByText(selectedPRODUCTSUBCAT_NAME).Selected = true;
                }
            }
            catch (Exception ex)
            { }
        }

[works with last row only]
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