Warning: count(): Parameter must be an array or an object that implements Countable in /home/cbc8fzob0jbt/domains/ on line 65

When trying to execute an SSIS package in Visual Studio 2012, I got the following error:

Method not found: ‘Boolean

Stackoverflow pointed me in the right direction,, but I needed to execute the gacutil.exe from the C:\Windows\System32 directory instead of the SDK folder.

C:\Windows\System32>gacutil.exe /if "C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\PrivateAssemblies\Microsoft.SqlServer.Dts.Design.dll"
Microsoft (R) .NET Global Assembly Cache Utility.  Version 4.0.30319.18020
Copyright (c) Microsoft Corporation.  All rights reserved.

Assembly successfully added to the cache

Now that the assembly is successfully added, restart Visual Studio 2012.