How to add reference to an assembly if different ver. exists

Prathap first thing you can add 2 or more same assembly with different version.

 

Now your question is how to choose a specific version in your application?

 

So just once go through below process:

 

Right click on "Reference" folder in your application  "Solution Explorer".

 

Now choose "Add Reference".

 

So now "Reference Manager" window will come. 

 

 From here you can choose the required assembly version as per your requirement (Here you will see the references group by like Framework, Extensions).

 

 

 

 

 

If this is helpful for you then please accept my Answer.