Could not load type ‘System.ServiceModel.Activation.HttpModule’ after installing the .NET Framework 4.0

After Installing a .NET Framework 4.0. If you decided to

• Install an earlier version of the .NET Framework,
• Or enable .NET 3.0 WCF HTTP Activation.

You might get the following error message

Could not load type ‘System.ServiceModel.Activation.HttpModule’

When you tried to brows a web applications that has been hosted on Internet Information Services (IIS)

Cause :

This issue occurs because the Applicationhost.config file for Windows Process Activation Service (WAS) has the following section defined,

<add name="ServiceModel" type="System.ServiceModel.Activation.HttpModule,
 System.ServiceModel, Version=3.0.0.0, Culture=neutral,
 PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />

Where this section is incompatible with the .NET Framework 4.0.

Solution:

• Go to Applicationhost.config file that located in %windir%\system32\inetsrv\config
• Open Applicationhost.config for edit and search for  ServiceModel

• Replace the following Tag

<add name="ServiceModel" type="System.ServiceModel.Activation.HttpModule,
 System.ServiceModel, Version=3.0.0.0, Culture=neutral,
 PublicKeyToken=b77a5c561934e089" preCondition="managedHandler" />

• By the following tag

<add name="ServiceModel" type="System.ServiceModel.Activation.HttpModule,
 System.ServiceModel, Version=3.0.0.0, Culture=neutral,
 PublicKeyToken=b77a5c561934e089" 
preCondition="managedHandler,runtimeVersionv2.0" />

• Save the file.
• Go back to browse your site that should be now working properly.

Second Solution

• Go to Start Menu > Run > cmd.
• Type the following command

cd  %windir%\Microsoft.NET\Framework\v4.0.30319 -->> aspnet_regiis.exe /iru

This also should be solve the issue.

Enjoy 🙂