getting text box value null when giving dynamically using repeater

if (detail_repeat.Items.Count > 0)
{
    for (int count = 0; count < detail_repeat.Items.Count; count++)
    {
        // RadioButton rd1 = (RadioButton)Repeater1.Items[count].FindControl("rbAccept");
        TextBox quantitytext = (TextBox)detail_repeat.Items[count].FindControl("txt_quan");
        // TextBox quantitytext = ri.FindControl("txt_quan") as TextBox;
        //Label productprice = detail_repeat.FindControl("lbl_price") as Label;
        Label productprice = (Label)detail_repeat.Items[count].FindControl("lbl_price");

        quantityText = quantitytext.Text;
        productpriceText = productprice.Text;
    }
}

<asp:Repeater ID="detail_repeat" runat="server" OnItemCommand="detail_repeat_ItemCommand">

    <ItemTemplate>

        <div>
            <div>
                <div class="detail_image">
                    <img src='<%#getpath()%><%# DataBinder.Eval(Container.DataItem, "Image")%>' />
                </div>
                <div id="detail_details">
                    <div class="detail_content">
                        <div class="detail_label">
                            <asp:Label runat="server" Text="PRODUCT NAME"></asp:Label>
                        </div>
                        <div class="detail_value">
                            <asp:Label ID="lbl_productname" runat="server" Text='<%# Eval("product_name") %>'></asp:Label><br />
                        </div>
                    </div>
                    <div class="detail_content">
                        <div class="detail_label">
                            <asp:Label runat="server" Text="PRODUCT QUANTITY"></asp:Label>
                            <asp:Label ID="lbl_quanstar" runat="server" Text="" Style="color: red">*</asp:Label>
                        </div>
                        <div class="detail_value">

                            <asp:TextBox ID="txt_quan" runat="server" Width="20px" ReadOnly="false" Text=""></asp:TextBox><br />
<asp:RequiredFieldValidator ID="Rreqval_quantity" runat="server" ValidationGroup="detail" ControlToValidate="txt_quan" ErrorMessage="Quantity is mandatory"></asp:RequiredFieldValidator>
                        </div>
                    </div>
                    <div class="detail_content">
                        <div class="detail_label">
                            <asp:Label runat="server" Text="PRODUCT PRICE"></asp:Label>
                        </div>
                        <div class="detail_value">
                            <asp:Label ID="lbl_price" runat="server" Text='<%# Eval("price")%>'></asp:Label><br />
                        </div>
                    </div>
                    <div class="detail_content">
                        <div class="detail_label">
                            <asp:Label runat="server" Text="PRODUCT DESCRIPTION"></asp:Label>
                        </div>
                        <div class="detail_value">
                            <asp:Label ID="lbl_description" runat="server" Text='<%# Eval("descrip")%>'></asp:Label><br />
                        </div>
                    </div>
                </div>
            </div>
    </ItemTemplate>
</asp:Repeater>