To set the Meta Tags in ASP.NET 4 you should use the MetaKeywords and MetaDescription properties which are members of the Page class.
You can set these properties at run time, so you get the content from a database or other source, and which lets you set the tags dynamically.
You can also set the Keywords and Description properties in the @ Page directive at the top of the Web Forms page:
<%@ Page Language=”C#” AutoEventWireup=”true”
Keywords=”some sample keywords”
Description=”Some sample description” %>