While working on this demo project, I got this error below
Problem with UseInMemoryDatabase Method
Severity Code Description Project File Line Suppression State Error CS1061 'DbContextOptionsBuilder' does not contain a definition for 'UseInMemoryDatabase' and no accessible extension method 'UseInMemoryDatabase' accepting a first argument of type 'DbContextOptionsBuilder' could be found (are you missing a using directive or an assembly reference?) WebDemoProject C:\Users\J\Startup.cs 32 Active
According to EntityFramework Core, in order to be able to use the InMemory reference, you need to have Microsoft.EntityFrameworkCore.InMemory package installed to have access to UseInMemoryDatabase() extension method with DbContextOptionsBuilder. Once I read that and installed it. Voila everything works like champ.