Default.aspx with IIS 6.0 and .Net 4?

Question

1. We have deployed a .net 4 asp.net site on IIS 6.0.
2. Default.aspx is configured as one of the default document.
3. When we access the site using the following url

http://testsite

We expect it to render

http://testsite/Default.aspx

But instead we get 404 Not found error. We did not had this issue when it was deployed on .Net 2.0. Only thing that has changed on the server is that we use .NET 4 instead of .NET 2.0.

UPDATE: I tried the following link but it did not work.

Getting an ASP.NET 4 application to work on IIS6

The framework version on the server is .NET 4 RC. Will it help if we install the latest .NET 4 version on the server?

Update: The issue is resolved now. The problem was a Third party upload control that we were using which added its own HttpHandler in Web.Config. This HttpHandler started failing in the .NET 4.

Answer 1

With the new .NET 4 framework, comes some problems if you are running it on IIS 6 Windows Server. IIS 6 does not let you have more than one framework at the time running in the same instance like IIS7 that can create Application Pool targeting different framework. When IIS 6 runs under ASP.NET 2.0 (3.0 and 3.5 are superset, not frameworks) you are going to hit this error if the application is 4.0 Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.

Source Error: 
Line 11:     </configSections> 
Line 12:     <system.web> 
Line 13:         <compilation debug="true" targetFramework="4.0"> 
Line 14:         </compilation> 
Line 15:         <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID"/>   </ system.web>

You have a few options;

1. Downgrade the .NET application to 3.5 that Visual Studio 2010 makes it really easy. Just go to the Website properties -> Application tab and there is a drop down with all the framework releases, select 3.5, you VS2010 will reload the project and modify the web.config, if you added web service reference, that you may have to delete them and re-add them under 3.5

2. To configure the IIS6 and web config to solve the issue. I deal with the second part:

3. In IIS 6 console, you need to right click you project and click the property and check the ASP.Net tab whether Framework 4 is selected or not. If not select the framework 4.

But still you might face the same error because of the application pool; you might have same application pool for two different framework web application. IIS 6 does not let you have more than one framework at the time running in the same instance (means single application pool can’t use for two different frameworks) like IIS7 that can create Application Pool targeting different framework.

2. To solve this issue you need to create application pool and assigned this application pool to you framework 4 web application. To assign the application pool, in IIS console open the properties section of the web application, and click on the “Home directory” tab and selection application pool which you have created earlier from drop-down-list.
3. This two might now solve your problem completely sometime. You can get the error as “404 Page is not found”. Though you might now have any issue while in development time.
4. Basically page is not found issue is cause of other problem which is set hidden by is IIS6 . But you need to see the real cause. What you have do here is go to the IIS6 console open “web service extension node” which is right below the “default website” node. You will see the entire ASP.Net framework list over there, by default these frameworks might be prohibited so please select ASP.Net Framework 4 and click allow button. Browse you website now, you get other error beside “404 Page is not found”. You might get the error as listed below:
5. The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' You’ll see following error when browsing the website The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework. To compile this Web application for version 3.5 or earlier of the .NET Framework, remove the 'targetFramework' attribute from the element of the Web.config file. To solve this issue, you need to modify your web config file as below:

Previously the CompilerVersion value is set as v3.5 but we already change our targetFranework to 4. Thus according to the error message above the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework.

Hence your new setting will be as below:

    <providerOption name="CompilerVersion" value="v3.5"/>

Hope this will solve your ASP.Net 4 migration and hosting issue at IIS6.