Could not load type System.ServiceModel.Activation.HttpModule

If you install DotNet framework 4.0 on IIS server and then enable .NET 3.0 or 3.5 WCF features, you might see following error when browse your application site made of ASP.NET 4.0 (or run on ASP.NET 4.0 application pool).

Could not load type ‘System.ServiceModel.Activation.HttpModule' from assembly ‘System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′.   
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.    
Exception Details: System.TypeLoadException: Could not load type ‘System.ServiceModel.Activation.HttpModule' from assembly ‘System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′.

Solution:

To resolve this issue, run the following command line: aspnet_regiis.exe /iru

The Aspnet_regiis.exe file can be found in one of the following locations:

%windir%\Microsoft.NET\Framework\v4.0.30319

%windir%\Microsoft.NET\Framework64\v4.0.30319 (on a 64-bit computer)