Could not load file or assembly "Microsoft.DataTransformationServices.Design,Version=12.0.0.0,Culture=neutral,PublicKeyToken=89845dcd8080cc91" or one of its dependencies.

Error

When I open SSIS project in VS 2012, the following error occurred:

 

The root cause:

I install SqlServer 2014 firstly, then I intall sql server 2012, in this condition, it will lead sql server 2012 overwrote the required version of Microsoft.DataTransformationServices.Design.DLL.

The solution:

 Use the Gacutil.exe (Global Assembly Cache Tool) to install Microsoft.DataTransformationServices.Design.DLL again for both sql server 2012 and sql server 2014.

1.Find the "Developer Command Prompt for VS 2012", then run it as administrator, in put following command, then it will show you have import the assembly successfully.

gacutil /i "C:Program Files (x86)Microsoft SQL Server110ToolsBinnManagementStudioMicrosoft.DataTransformationServices.Design.DLL"

2.Find the "Developer Command Prompt for VS 2013", then run it as administrator, in put following command, then it will show you have import the assembly successfully.

gacutil /i "C:Program Files (x86)Microsoft SQL Server120ToolsBinnManagementStudioMicrosoft.DataTransformationServices.Design.DLL"

Reference:

You can refer following url for more infomation of Global Assembly cache tool:

https://msdn.microsoft.com/en-us/library/ex0ss12c(v=vs.110).aspx

You can reference following two url for more detail info:

https://blogs.msdn.microsoft.com/junfeng/2004/03/25/the-located-assemblys-manifest-definition-with-name-xxx-dll-does-not-match-the-assembly-reference/

http://www.solvusoft.com/en/files/missing-not-found-error/dll/windows/microsoft/msdn-disc-2729/microsoft-datatransformationservices-design-dll/