Trying to view custom application page in browser results in "404 FILE NOT FOUND" error

Question

In VS2010 I created a new .NET 3.5 solution and inside a new project for SharePoint 2010 (empty project called "SPAppPageTest"); I deployed it as a farm solution. I added a new application page, called CustomApplicationPage1.aspx via add - new item solution explorer menu - I didn't change the page. Here's what my project layout looks like:

I deploy this by right-clicking the project -> Deploy. In directory C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS I can after this see a "SPAppPageTest" folder with a file "CustomApplicationPage1.aspx". However, trying to view the page in browser (Firefox or Chrome) results in "404 FILE NOT FOUND" page being displayed (in IE I get "This webpage cannot be found"). The URL I'm entering is:

http://<server>/_layouts/SPAppPageTest/CustomApplicationPage1.aspx

What am I doing wrong?

Here's how CustomApplicationPage1.aspx looks like (I haven't changed it, it's the default code that VS generates):

<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>
<%@ Import Namespace="Microsoft.SharePoint.ApplicationPages" %>
<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>
<%@ Import Namespace="Microsoft.SharePoint" %>
<%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="CustomApplicationPage1.aspx.cs" Inherits="SPAppPageTest.Layouts.SPAppPageTest.CustomApplicationPage1" DynamicMasterPageFile="~masterurl/default.master" %>

<asp:Content ID="PageHead" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server">

</asp:Content>

<asp:Content ID="Main" ContentPlaceHolderID="PlaceHolderMain" runat="server">

</asp:Content>

<asp:Content ID="PageTitle" ContentPlaceHolderID="PlaceHolderPageTitle" runat="server">
Application Page
</asp:Content>

<asp:Content ID="PageTitleInTitleArea" ContentPlaceHolderID="PlaceHolderPageTitleInTitleArea" runat="server" >
My Application Page
</asp:Content>

Answer 1

The first thing that comes to mind is the URL of your site. It appears everything that you've done is correct as far as the project setup and deployment.

The URL of your site needs to be a valid site collection, not just the server name, otherwise SharePoint won't handle the virtual path properly.

So instead of:

http://<server>/_layouts/SPAppPageTest/CustomApplicationPage1.aspx

Make sure that it's:

http://avalidsitecollectionurl/_layouts/SPAppPageTest/CustomApplicationPage1.aspx

Seems like the most likely problem.