I recently converted a website project to a web application project in Visual Studio 2008. I finally got it to compile, and the first page (the login screen) displayed as normal, but then when it redirected to the Default.aspx page, I received an error:
Parser Error Message: 'SOME.NAMESPACE.MyApplicationName.WebApplication._Default' is not allowed here because it does not extend class 'System.Web.UI.Page'.
All of my pages inherit from a class called "BasePage" which extends System.Web.UI.Page. Obviously the problem isn't with that class because the login.aspx page displays without error, and it also inherits from that basepage.
All the pages on the site, including the login page, are children of a masterpage.
After some testing, I have determined what it is that causes the error (although I don't know WHY it does it).
On all the pages where I have the following tag, the error does NOT occur.
<%@ MasterType VirtualPath="~/MasterPages/MainMaster.master" %>
On all the pages that do not contain that line, the error DOES occur. This is throughout the entire application. I have the tag only on pages where there has been a need to reference controls on the MasterPage.
So, I thought I would just add that line to all my pages and be done with it. But when I add that line, I get a compile error: 'object' does not contain a definition for 'Master'
This error is coming from the designer.cs file associated with the ASPX page that I have added the "MasterType" declaration to.
I've forced a rebuild of the designer file, but that doesn't change anything. I compared the content of the Master reference in the designer files between the login.aspx (working) and the default.aspx (not working) but they are exactly the same.
Since I'd really like to get it to work without having to add the "MasterType" declaration to everypage, and since that "fix" isn't working anyway, does anyone know why not having the "MasterType" declaration on an aspx file causes the parser error? Is there a fix for this?
Example Code:
Here is the code for login.aspx and login.aspx.cs which is working without error:
Login.aspx
<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPages/MainMaster.master" AutoEventWireup="true" Inherits="SOME.NAMESPACE.MyApplicationName.WebApplication.Login" Codebehind="Login.aspx.cs" %>
<%@ MasterType VirtualPath="~/MasterPages/MainMaster.master" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder" Runat="Server">
<table>
<tr>
<td>
<asp:UpdatePanel ID="upLogin" runat="server">
<ContentTemplate>
<asp:Panel ID="Panel1" runat="server" DefaultButton="Login1$LoginButton">
<asp:Login ID="Login1" runat="server" LoginButtonStyle-CssClass="button"
TextBoxStyle-CssClass="textBoxRequired"
TitleTextStyle-CssClass="loginTitle" >
</asp:Login>
</asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
<asp:UpdatePanel ID="upPasswordRecovery" runat="server">
<ContentTemplate>
<asp:PasswordRecovery ID="PasswordRecovery1" runat="server"
SubmitButtonStyle-CssClass="button" TitleTextStyle-CssClass="loginTitle"
SuccessText="Your new password has been sent to you."
UserNameInstructionText="Enter your User name to reset your password." />
</ContentTemplate>
</asp:UpdatePanel>
</td>
</tr>
</table>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="SideBarPlaceHolder" Runat="Server">
<h2>Login</h2>
<asp:Button ID="btnCreateAccount" runat="server" Text="Create Account" OnClick="btnCreateAccount_Click" CausesValidation="false" />
</asp:Content>
Login.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using SOME.NAMESPACE.MyApplicationName.WebApplication;
using SOME.NAMESPACE.MyApplicationName.Bll;
namespace SOME.NAMESPACE.MyApplicationName.WebApplication
{
public partial class Login : BasePage
{
protected void Page_Load(object sender, EventArgs e)
{
Login1.Focus();
}
protected void btnCreateAccount_Click(object sender, EventArgs e)
{
Page.Response.Redirect("~/CreateUser/default.aspx");
}
}
}
Here is the code for default.aspx and default.aspx.cs which is throwing the parser error when viewed in a web browser:
Default.aspx
<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPages/MainMaster.master" AutoEventWireup="True" Inherits="SOME.NAMESPACE.MyApplicationName.WebApplication._Default" Codebehind="Default.aspx.cs" %>
<%@ MasterType VirtualPath="~/MasterPages/MainMaster.master" %>
<asp:Content ID="MainContent" ContentPlaceHolderID="ContentPlaceHolder" Runat="Server">
<div class="post">
<h2 class="title">Announcements</h2>
<p class="meta">Posted by Amanda Myer on December 15, 2009 at 10:55 AM</p>
<div class="entry">
<p>The MyApplicationName CMDB will be down for maintenance from 5:30 PM until 6:30 PM on Wednesday, December 15, 2009.</p>
</div>
<p class="meta">Posted by Amanda Myer on December 01, 2009 at 1:23 PM</p>
<div class="entry">
<p>The MyApplicationName CMDB is officially live and ready for use!</p>
</div>
</div>
</asp:Content>
<asp:Content ID="SideBarContent" ContentPlaceHolderID="SideBarPlaceHolder" Runat="Server">
<img src="images/MyApplicationName.jpg" alt="MyApplicationName Gremlin" width="250"/>
</asp:Content>
Default.aspx.cs
using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using SOME.NAMESPACE.MyApplicationName.Bll;
using SOME.NAMESPACE.MyApplicationName.WebApplication;
public partial class _Default : BasePage
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
Thanks!
I figured it out. The problem was that there were still some pages in the project that hadn't been converted to use "namespaces" as needed in a web application project. I guess I thought that it wouldn't compile if there were still any of those pages around, but if the page didn't reference anything from outside itself it didn't appear to squawk. So when it was saying that it didn't inherit from "System.Web.UI.Page" that was because it couldn't actually find the class "BasePage" at run time because the page itself was not in the WebApplication namespace. I went through all my pages one by one and made sure that they were properly added to the WebApplication namespace and now it not only compiles without issue, it also displays normally. yay!
what a trial converting from website to web application project can be!
I had this issue, as I had copied a (fairly generic) webpage from one of my ASP.Net applications into a new application.
I changed the relevant namespace commands, to reflect the new location of the file... but... I had forgotten to change the Inherits parameter in the aspx page itself.
<%@ Page MasterPageFile="" StylesheetTheme="" Language="C#"
AutoEventWireup="true" CodeBehind="MikesReports.aspx.cs"
Inherits="MikesCompany.MikesProject.MikesReports" %>
Once I had changed the Inherits parameter, the error went away.
Look for this:
ANY page in your project that has a missing, or different Namespace...
If you have ANY page in your project with <NO Namespace> , OR a
DIFFERENT Namespace than Default.aspx, you will get this
"Cannot load Default.aspx", or this: "Default.aspx does not belong here".
ALSO: If you have a Redirect to a page in your Solution/Project and the page which is to be Redirected To has a bad namespace -- you may not get a compiler error, until you try and run. If the Redirect is removed or commented-out, the error goes away...
BTW -- What the hell do these error messages mean? Is this MS.Access, with the "misdirection" -- ??
DGK
I had copied and renamed the page (aspx/cs). The page name was "mainpage" so the class name at the top of the cs file as follows:
After renaming the class to match this error was resolved.
I had a similar error but not from a Conversion...
System.Web.HttpException: 'Namespace.Website.MasterUserPages' is not allowed here because it does not extend class 'System.Web.UI.MasterPage'
I was also extending the MasterPage class.
The error was due to a simple compilation error in my Master Page itself:
System.Web.HttpCompileException: c:\directory\path\Website\MasterUserPages.Master(30): error CS1061: 'ASP.masteruserpages_master' does not contain a definition for 'btnHelp_Click' and no extension method 'btnHelp_Click' accepting a first argument of type 'ASP.masteruserpages_master' could be found (are you missing a using directive or an assembly reference?)
I was not able to see the error until I moved the MasterPage to the root website folder. Once that was taken care of I was able to put my MasterPage back in the folder I wanted.
For me I had all of the namespaces on the pages and none of the solutions above fixed it. My problem was in:
<%@ Page Language="C#"
AutoEventWireup="true"
CodeBehind="xxx.aspx.cs"
Inherits="xxx.xxx.xxx"
MasterPageFile="~masterurl/default.master" %>
Then in my aspx.cs file the namespace did not match the Inherits tag. So it needed
namespace xxx.xxx.xxx
In the .cs to match the Inherits.
My issue was simple: the Master page and Master.Designer.cs class had the correct Namespace, but the Master.cs class had the wrong namespace.
You can always refractor the namespace and it will update all the pages at the same time. Highlight the namespace, right click and select refractor from the drop down menu.
I delete that web page that i want to link with master page from web application,add new web page in project then set the master page(Initially I had copied web page from web site into Web application fro coping that aspx page (I was converting website to web application as project))
Remember.. inherits is case sensitive for C# (not so for vb.net)
Found that out the hard way.
来源：https://stackoverflow.com/questions/2057817/parser-error-default-is-not-allowed-here-because-it-does-not-extend-class-s