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App won;t run on .net 4.0 framework

No1Coder used Ask the Experts™
Am trying to upgrade a customer to .net 4.0 with a new app.

He created a new web site, and points at dedicate app pool (W 2003), and targets 4.0.  Gets a page not found error (404).

The app is compiled for .net 4.0.  Have made the web.config changes for the 4.0 upgrade:
<compilation defaultLanguage="c#" debug="true" targetFramework="4.0">
<pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID"/></system.web>

This same app working in multipel places on multiple servers.  Can't figue out what is wrong here.

If I point the web site at a 2.0 application, and change the .net to 2.0, it works. If I then change to .net 4.0, it will not work.  So neither the 2.0 or 4.0 application will work on the 4.0 framework.

Tried reinstall/repair of the framework itself.  Tried restarting server.


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Alexandre SimõesManager / Solutions Architect

On IIS, set the application pool of the site to ASP.net v4.0 Classic instead of just ASP.net v4.0


The server is Windows 2003 (IIS 6).  I don;t this this is an option.  If so, when can I find it?
It is located on the ASP.NET tab under the properties of an IIS website.

See attached screenshot.