FYI | ctrl + K, C is the comment shortcut in Visual Studio. ctrl + K, U uncomments.
I believe you're looking for:
<%-- your markup here --%>
That is a serverside comment and will not be delivered to the client ... but it's not optional. If you need this to be programmable, then you'll want this answer :-)
Yes, there are special server side comments:
<%-- Text not sent to client --%>
While this works:
<%-- <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="ht_tv1.Default" %> --%>
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Blank._Default" %>
This won't.
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" <%--Inherits="ht_tv1.Default"--%> Inherits="Blank._Default" %>
So you can't comment out part of something which is what I want to do 99.9995% of the time.
Bonus answer: The keyboard shortcut in Visual Studio for commenting out anything is Ctrl-KC . This works in a number of places, including C#, VB, Javascript, and aspx pages; it also works for SQL in SQL Management Studio.
You can either select the text to be commented out, or you can position your text inside a chunk to be commented out; for example, put your cursor inside the opening tag of a GridView, press Ctrl-KC, and the whole thing is commented out.
<%-- not rendered to browser --%>
Another way assuming it's not server side code you want to comment out is...
<asp:panel runat="server" visible="false">
html here
</asp:panel>
Source: Stackoverflow.com