can't debug asp.net - "unable to start program"

I cannot debug an asp.net application. Nothing was changed or installed on purpose, maybe some automatic updates, which I thought were turned off. Just woke up one day and whe开发者_C百科nver I try to debug, I get the mesage "Unable to start program http://localhost:49404/Default.aspx". This is Visual Studio 2008 on Vista Business 64 bit. Facts: -neither applications that use IIS or the built in webserver will debug -applications will run without debugging (debug build, just run) -visual studio, iis, and the dot net 3.5 sdk have been reisntalled. Any ideas? This is going on days trying to figure this out. About to reisntall vista. Brian

Did the addressing change? Is the site still on port:49404?

Have you any antivirus running on your vista box? Which one?
When you start debugging, a little cloud appears on the bottom right side of your screen, it indicates the port cassini's server is running on. Is this port the same as 49404?

Here are some pointers and tips:

• check the output of this program \Windows\Microsoft.NET\Framework\v2.0.XXXX\WebDev.WebServer.exe
• Did your default project change?
• Is your default browser working correctly?

Before you reinstall OS you may want to

• reinstall ASP.Net (aspnet_regiis.exe)
• reinstall your default browser

Crazy, but may solve the problem. Try this: Start without debug (ctrl+F5), and when IE opens, start again in debug mode (F5). Dont exit from IE, just stop debug in VS2008.

I had this exact problem with Visual Studio 2008. The solution was to set the default web browser that VS uses to a real browser (e.g. IE) and not the "Internal Web Browser".

1. Right click on an ASPX file in your project and select "Browser With...". This lets you select the default browser to use when you select the "View in Browser" option and for when you debug/run the app (this is key).
2. Select your favourite browser (i.e "Internet Explorer") and click on "Set as Default". Do not pick "Internal Web Browser".
3. Debug away! Your app should come up in your browser now and debug as normal.