new handler triggers debug failure in visual studio - asp.net

Question

I have an existing asp.net website that works. When I (F5) debug it works. However, I am working on a new IHttpHandler for the site. As soon as I add the <system.webServer><handler></handler></system.webServer> section to the web.config visual studio refuses to F5 debug with the error:
Unable to start debugging on the web server. The web server could not
find the requested resource.
With the handler in place, if I attach-to-process then I can successfully attach to the process (and with the System.Diagnostics.Debugger.Break(); line I can step through the handler's code). I also added my handler to a different website and was able to reproduce this issue.
My Environment: .NET 4.0, Visual Studio 2012, using local IIS in integrated mode on Windows 7.
While trying to sanitize the code to paste here, I ended up commenting out everything in my handler except the boiler-plate, and the issue still occurs. Here are the code snippets:
The handler class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace MySvc
{
public class MyServiceHandler : IHttpHandler
{
public bool IsReusable
{
get { return false; }
}
public void ProcessRequest(HttpContext context)
{
//#if DEBUG
// System.Diagnostics.Debugger.Break();
//#endif
}
}
}
and the web.config:
<?xml version="1.0"?>
<configuration>
<appSettings>
<clear/>
<add key="A1" value="sanitized"/>
<add key="A2" value="sanitized"/>
</appSettings>
<connectionStrings>
<clear/>
<add name="MyDatabase" connectionString="sanitized"/>
</connectionStrings>
<system.web>
<compilation debug="true"/>
<httpRuntime maxRequestLength="1048576" executionTimeout="3600"/>
<sessionState mode="SQLServer" cookieless="false" timeout="5" allowCustomSqlDatabase="true" cookieName="My.Session"
sqlConnectionString="sanitized" />
<machineKey
validationKey="sanitized"
decryptionKey="sanitized"
validation="sanitized" decryption="sanitized" />
</system.web>
<system.webServer>
<handlers>
<clear />
<add name="MyHandler" path="*.bwsvc" verb="*" type="MySvc.MyServiceHandler, MySvc" />
</handlers>
</system.webServer>
</configuration>
I've read through The Web Server Could Not Find the Requested Resource and many other articles along the same lines. None of it seems applicable to this situation, nothing mentions handlers causing problems.
Am I missing something in my handler or is this something Visual Studio doesn't support or some other issue?

Answer 1

I found the problem. It turns out the <clear /> in the <handlers> section was responsible for causing the problem. As soon as that line is removed, the debugger works again (and many other things too).
Since my application pool is in integrated pipeline mode, the handlers section actually inherits from the server settings which specify what handles such core things as *.aspx and such, so doing a clear on it means that IIS didn't know what to do with anything in my application.