How to upgrade to ASP.NET4

If you want to know how to upgrade your existing ASP.NET solution to target the ASP.NET 4 framework there are a number of steps you need to take to ensure a smooth upgrade of your website. ASP.NET 4 is a brand new framework, it is not just an extension of ASP.NET 3.5. This means there are a number of steps you need to know to know how to successfully upgrade to the new .NET4 runtime smoothly.

Here is a list of challenges I encountered whilst upgrading the lovemoney.com solution to ASP.NET 4 from ASP.NET 3.5. I hope you find this an important reference or guide if you come to do the same thing:

1. Set your application pool to use .NET 4
2. Changing the browser definitions
3. Running .NET 4 application as a child under a .NET 3.5 root parent site in IIS 7
4. Targeting ASP.NET 3.5 with MSTest
5. Potentially dangerous request validation
6. MembershipUser and other System.Web.Security types have moved namespace
7. Publishing a project with missing files

1. Set your application pool to use .NET 4

You may run into an error saying "Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive." with a description of "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."

This is indicating that your solution is targeting the .NET 4 framework but is still using the .NET 2 framework. To fix this you need to:

1. Go to IIS
2. Find the Application Pool you are using
3. Right click it and select Basic Settings
4. Change the target framework to .NET Framework v4 as illustrated

More info on unrecognized targetFramework attribute in ASP.NET 4

2. Changing the browser definitions

You could receive an error message of "The browser or gateway element with ID 'Safari1Plus' cannot be found." and a description of "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."

This is because the browser definitions have been updated for ASP.NET 4 from the 5 year old ASP.NET 2 browser definitions.

If you have not added to your browser definitions in any way your site should work okay but be aware that some browsers may be identified more (or maybe less) accurately. If you added to your browser definitions prior to the .NET4 upgrade (i.e. there are files in your App_Browser folder) you may recieve errors. These errors will be immediately apparent runtime errors.

If you are getting these runtime errors you can fix them in one of two ways:

• Remove the browser definitions you have in the web root's App_Browsers folder
• Copy the old browser definition files from the old location of C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG\Browsers to C:\Windows\Microsoft.NET\Framework\v4.0.[whatever]\Config\Browsers (you will also need to do the same for the Framework64 version if you have one) and then run the Aspnet_regbrowsers.exe command-line tool.

More info on browser or gateway element not being found in browser definitions

3. Running .NET 4 application as a child under a .NET 3.5 root parent site in IIS 7

You get the error of "The requested page cannot be accessed because the related configuration data for the page is invalid." and a config error of "There is a duplicate 'system.web.extensions/scripting/scriptResourceHandler' section defined"

This is because your web.config of your child site or application is inheriting from you parent application or site. This would happen if you have made an ASP.NET 4 application a child of an ASP.NET 2 or 3.5 site.

A (filthy) workaround for this problem would be to:

1. Move the whole <configSections> section into the machine level web.config at C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG\
2. stop the web.config inheritance to wrap the whole configuration section in a <location inheritInChildApplications="false">

This feel very messy and personally I am not a fan of changing machine level configs, I went for upgrading the root site.
If you want more detailed info than this please feel free to bore dive into ASP.NET 4 Child Applications Fail to Start When Under ASP.NET 2.0 or ASP.NET 3.5 Applications - (and good luck!)

More info on duplicate section defined in a child .NET 4 application

4. Targeting ASP.NET 3.5 with MSTest

You may run into an "attempted re-targeting of the project has been cancelled. You cannot change the specified .NET framework version or profile for a test project" error when you try to target the ASP.NET 3.5 framework in a Microsoft Unit Test project.

Seriously, that is the end of this step. You just can't do it. Deal with it. This comes from Microsoft's mouth too (slightly more elegantly, I will concede). But, the fact remains: You cannot use Visual Studio 2010 AND target ASP.NET 3.5 AND use MS Test.

You will either have to exclude the Unit Test project from your solution or not use VS2010!

More info on changing the specified .NET framework version or profile for a test project

5. Potentially dangerous request validation

You can find yourself with an error of "A potentially dangerous Request.Form value was detected from the client" on a page which is set to ValidateRequest="false".

Previously putting ValidateRequest="false" in the Page declaration solved this problem. In .NET4 this is not the case. Simple work around though. You simply need to stick the following code in your web.config:

<system.web>
    <httpRuntime requestValidationMode="2.0" />
    <!-- everything else -->
</system.web>

This will set the request validation back to how you are used to. However, why not use this opportunity to solve this potential security properly? Or maybe use a <location inheritInChildApplications="false"> to wrap this code so that it is only relevant to the specific page that needs it?

More info on potentially dangerous request in ASP.NET 4 upgrade

6. MembershipUser and other System.Web.Security types have moved namespace

You could get a build time error of "The type name 'MembershipProvider' could not be found in the namespace 'System.Web.Security'. This type has been forwarded to assembly 'System.Web.ApplicationServices, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' Consider adding a reference to that assembly. ASP.NET4." after upgrading.

To fix this you just need to add a reference to the erroring project(s).

1. Right click the References folder
2. Click Add Reference...
3. Under the .NET tab find and select System.Web.ApplicationServices

You may now need to resolve the references to MembershipUser (or other types) but you should be good to go.

More info on Membership provider not being found in System.Web.Security

7. Publishing a project with missing files

It seems like Visual Studio 2010 is a lot less forgiving when it comes to the project file referencing a file (static (e.g. an image) or otherwise) that does not actually exist when publishing.

You will have to go about your solution excluding all of these dud references. One by one too! Publish then exclude, publish, exclude, publish, exclude etc. until it published okay and stops complaining.

Summary and more...

This is a list of the complications I encountered during the upgrade process and how to solve each one. There are other complications too that I didn't personally encounter which you can read a white paper on ASP.NET 4 breaking changes from Microsoft themselves.

Hope this helps - if it did please link to this guide.

Good luck!