Upgrading class library from 2.0 to 4.0 .Net Framework

Hi,

I have a class library, .Net  visual studio 2012 solution, which creates SSIS package at run time. SSIS packages are created with the help of following dlls:Microsoft.SqlServer.DTSPipelineWrap,Microsoft.SQLServer.DTSRuntimeWrap,Microsoft.SQLServer.ManagedDTS

location of these dlls were :C:\Program Files (x86)\Microsoft SQL Server\100\SDK\Assemblies\

This solution is on .Net 2.0  framework. I am using this dll on a DB server to create and execute SSIS package at run time.

Now, I was asked to move the framework from 2.0 to 4.5. IN the process of migrating the framework, I referenced the above 3 dlls from location : 

C:\Program Files (x86)\Microsoft SQL Server\110\SDK\Assemblies\

and compiled the solution selecting .Net framework 4.5 from the properties window. Solution compiled successfully. 

I deployed the dll but getting below error :

Attempt by method ETLLibrary.ETLExtractor.ExecuteSSISPackage(Boolean, System.String, System.String, System.String, System.String, System.String) to access method ETLLibrary.ETLPackage.Create() failed.

ETLLibrary is the name of project. ETLExtractor is a class with the project. ExecuteSSISPackage is a method with the class. 

Please help me as I am not a .Net resource and I am not sure if I am missing anything else to migrate my code from .Net 2.0 framework to .Net 4.5 framework..