in asp.net the simplest way is to use a Panel that warps the textboxes, and what ever user fills, and set DefaultButton
to the action you wont when the user press Enter for the included text boxes.
<asp:Panel runat="server" ID="pnlAct" DefaultButton="Button1">
<asp:TextBox runat="server" id="txt_home">Add Comment</asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button" />
</asp:Panel>
Of course you can use custom javascript to capture the Enter and make custom post back, but asp.net all ready gives you a safe and "ready to use solution".