A master page starts with a Master directive that specifies the same information.
<%@ Master Language="C#"
AutoEventWireup="true"
CodeFile="Default.master.cs"
Inherits="SiteTemplate" %>
The ContentPlaceHolder is like any ordinary control.
<%@ Master Language="C#"
AutoEventWireup="true"
CodeFile="Default.master.cs"
Inherits="SiteTemplate" %>
Untitled Page
ASP.NET links your page to the master page with attribute named MasterPageFile
<%@ Page Language="C#"
MasterPageFile="~/Default.master"
AutoEventWireup="true"
CodeFile="SimpleContentPage.aspx.cs"
Inherits="SimpleContentPage"
Title="Untitled Page" %>
path ~/ is to specify the root website folder.
The Page directive has another new attribute Title.
Title attribute overrides the title specified in the master page.
The content page can¡Â¯t define anything provided in the master page,
including the section,
the root element,
the element, and so on.
The content page supply a Content tag that corresponds to the ContentPlaceHolder in the master page.
<%@ Page Language="C#"
MasterPageFile="~/Default.master"
AutoEventWireup="true"
CodeFile="SimpleContentPage.aspx.cs"
Inherits="SimpleContentPage"
Title="Content Page" %>
Here's some new content!
ContentPlaceHolderID attribute in the tag must match the ContentPlaceHolder specified in the master page exactly.