Plugin with data access tutorial, missing reference?

Hi everyone.

I'm trying to follow this tutorial https://docs.nopcommerce.com/display/en/Plugin+with+data+access for creating a plugin with data access.

I managed to build my first class okay but i've ran into an error on the Entity Framework mapping class.

I've copied the content from the tutorial, but it complained about missing references, so I added Nop.Data.Mapping and Nop.Plugin.Other.ProductViewTracker.Domain as it suggested.

But now I get the error Add reference to 'EntityFramework...' as seen below.



How do I go about adding a reference to this? When I click add reference a box appears as below



If anyone could point me in the right direction that would be great.

Hello,

Please add manually reference of entity framework.dll by ri8 click on reference and click on add reference.

You should copy path(entity framework.dll) of existing default nopcommerce plugin.