in ASPX bootstrap v4.0.0, no beta (dl 21-01-2018)
<div class="input-group">
<asp:TextBox ID="txt_Product" runat="server" CssClass="form-control" placeholder="Product"></asp:TextBox>
<div class="input-group-append">
<asp:LinkButton ID="LinkButton3" runat="server" CssClass="btn btn-outline-primary">
<i class="ICON-copyright"></i>
</asp:LinkButton>
</div>