I get the following error after installing SQL Server 2014 on a PC that already has SQL Server 2012. What I've noticed is the said DLL's move up from version 11 to 12 automatically when opening the project:
Error:
Error 1 Assembly 'Microsoft.SqlServer.Management.IntegrationServices, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' uses 'Microsoft.SqlServer.Management.Sdk.Sfc, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' which has a higher version than referenced assembly 'Microsoft.SqlServer.Management.Sdk.Sfc, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' c:\Windows\assembly\GAC_MSIL\Microsoft.SqlServer.Management.IntegrationServices\12.0.0.0__89845dcd8080cc91\Microsoft.SqlServer.Management.IntegrationServices.dll
Best Answer
In your Solution Explorer, right click on references and Add Reference... On left panel: Assemblies > Extensions and search your assembly (v11.0.0.0), un-check the referenced assembly then check the new assembly (v12.0.0.0), click OK and clean the project solution, then rebuild.
I had this issue before and this fixed it. Hope this helps you!