WebApi and WebApp share a class library. How can I ensure the same build of the class library is used when either the WebApp or the WebApi is deployed?

Hello,

Originally, I had just a WebApp and it consisted of three projects/layers: WebApp -references Services -references Data Access.
Now, I have a WebApi and it uses the same Services library that the WebApp project uses: WebApi -references Services -references Data Access.
Everything is in the same solution and repository.

We now want to deploy the WebApp and WebApi simultaneously because they use the same Services library. (We wouldn't ever want two different versions of Services being used by different apps).

The main question I have is: Should we use separate Build Configurations or just add more Build Steps in the Configurations we already have?

Adding more Build Steps would look something like:

Configuration: Build
-Step 1: Build WebApp
-Step 2: Build WebApi

Configuration: Deploy
-Step 1: Deploy WebApp
-Step 2: Deploy WebApi

Adding new Configurations would look something like:

Configuration: Build_WebApp
-Step 1: Build WebApp

Configuration: Build_WebApi
-Step 1: Build WebApi

Configuration: Deploy
-Step 1: Deploy WebApp
-Step 2: Deploy WebApi

(Or possibly even two separate Deploy configurations?)

With adding new Configurations, I'm not sure how I could ensure the same build of the Services library is used.
Also, the references are direct project references...not sure if that makes a difference.