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In this video, we'll be completing
the first part of the setup process,

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adding the class library project.

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I've already downloaded
the ComicBookLibraryManager console app

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project files and opened the solution
in Visual Studio Community 2017.

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If you're following along,
see the teacher's notes for

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a link to download the files, or for
more information about Visual Studio.

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Before we make any changes,

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let's run the app to ensure that
everything works as expected.

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The first time that you run the app, EF
will check the default SQL Server LocalDB

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instance to see if the
ComicBookLibraryManager database exists.

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And if it doesn't exist,
EF will create and see the database.

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If you run into any database related
issues, see the teacher's notes for

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resources that will help you verify
that SQL Server LocalDB is installed and

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configured correctly for use with EF.

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Now that we've verified that
the console app is working correctly,

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let's add the class library project.

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In this Solution Explorer window, notice
that the ComicBookLibraryManager project

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is located underneath the Visual Studio
Solution named, ComicBookLibraryManager.

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A solution can contain one or
more projects, to add a new project

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right click on the solution and
select Add>New project.

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If you select the Visual C# category
on the left, you'll see that there's

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more than one project type that
contains the name Class Library.

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For our solution,

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we want the project type that is
named Class library (.NET Framework).

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For more information about
the .NET standard and

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the .NET standard Class Library
project type, see the teacher's notes.

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Name the project ComicBookShared.

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Verify that the selected .NET
Framework version is set

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to .NET Framework 4.6.1,
then click the OK button.

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The project template adds a file in
the root of the project name Class1.cs.

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Go ahead and delete that file.

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If we open the packages.config file in
the root of the console app project,

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we can see that the project
already has a reference to

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the EntityFramework NuGet package.

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Since we're moving our EF related
classes to the Class Library project,

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it also needs to have reference to
the EntityFramework NuGet package.

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To do that, right-click on the class
library project in Solution Explorer, and

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select Manage NuGet Packages.

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Select the Browse tab,
if it's not already selected, and

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install the EntityFramework package

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Go ahead and close all of the open tabs
once the package is finished installing.

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Now we're ready to move the EF related
classes to the Class Library project.

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The Data folder contains the Context,
DatabaseInitializer and

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Repository classes, while the Models
folder contains all of our indie classes.

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Visual Studio makes copying folders
between projects easy to do.

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Simply drag and drop the Data and

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Models folders from the console app
project to the Class Library project.

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Notice that I'm dragging the folders
onto the name of the project,

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in order to copy the folders
into the root of the project.

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We no longer need the Data and

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Models folder in the console app project,
so go ahead and delete them.

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If we open the Context.cs file,
we'll notice that the name space still

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reflects the file's original
project: ComicBookLibraryManager.

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Typically the first part of the name space
matches the name of the project that

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the files are contained within.

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This isn't a hard requirement,
we could leave the name space as it is.

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But I like to keep my code clean, and
it's simple enough to do, so let's fix it.

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Select the text
ComicBookLibraryManager and

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press Ctrl+H to open
the Quick Replace dialog.

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Set the replacement term
to ComicBookShared and

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the scope of the replacement
to the Current Project.

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Then press Alt+R to replace
references one at a time or

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Alt+A to replace them all at once,
which is what I'll do.

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Press Ctrl+Shift+S to
save all the open files.

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Now, let's update the console app project,

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first we need to add a reference
to the Class Library project.

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Right-click on References and
select Add Reference.

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On the left, make sure that projects is
selected, then select the ComicBookShared

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project and click OK.

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In the Program.cs file,

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we can see here in the scroll bar
there are numerous compilation errors.

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That's what these red areas represent, we
can right-click on the scroll bar, select

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Scroll Bar Options and set the vertical
scroll bar behavior to use map mode.

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Now we can just hover over one of the red
areas to see a pop-up preview of the code

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in that part of the file Artist, Role has
squiggles, ComicBook has red squiggles.

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Hm, looks like the compiler
is having trouble locating

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all of the types that we moved
to the Class Library project.

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Let's take a look at our using statements.

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Need to update a couple of using
statements here at the top of the file.

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Using ComicBookLibraryManager.Data, and
using ComicBookLibraryManager.Models.

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Both Data and Models are now located
in the ComicBookShared project.

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And now all of the areas that were
being shown in the scroll bar are gone.

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Let's run the app and
verify that everything is still working.

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If you need to,
right-click on the console app project and

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select Set as StartUp Project.

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So that Visual Studio will build and

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start that project instead of
the Class Library project.

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Visual Studio will bold the name
of the startup project, so

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that it's easy to identify
in the Solution Explorer.

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And, we got an error,
System.NotSupportedException.

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Model compatibility cannot be
checked because the database does

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not contain model metadata.

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Model compatibility can
only be checked for

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databases created using Code First or
Code First Migrations.

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This is an odd error,
at the beginning of this video,

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we were able to run the console app,
so what happened?

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Let's ensure that our
database actually exists.

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Open the SQL Server Object Explorer
window, and

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drill down to the list of databases.

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Here's our database.

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And a list of it's tables.

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Why would EF think that our database
wasn't created using the Code First

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workflow?

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Let's ask ourselves what
does EF do the first

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time that a DB set property is
accessed on the database context?

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If you're following along,
go ahead and pause the video, and

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see if you can troubleshoot
this error on your own.

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When you're ready to learn the solution,
unpause the video.

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How did you do,
were you able to resolve the error?

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The first time that a DB
set property is accessed

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on the database context EF will compare
the in memory representation of our model

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with the model queried from
the MigrationHistory table.

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An application can have more
than one database context.

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So in order for EF to retrieve
the model for the correct context,

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they'll filter the table rows
by the context key column value,

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which is the name of our context
class type, including its name space.

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We can see that our
context key column value

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is ComicBookLibraryManager .Data.Context.

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But we moved the context
class into the Class Library.

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And changed the classes root name
space to the ComicBookShared.

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Because of this change, EF wasn't able to
find the model data for our context class.

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Let's update the context key
column value to the correct value.

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ComicBookShared.Data.Context, close
the tab and run the app again.

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And now the app runs as expected.