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Now let's take a look at the Code First workflow, which allows you to define your model by directly writing the code for your entity and context classes. We'll also add the first entity to our model.
Code First from Existing Database
It's possible to use the Code First workflow with an existing database, by generating your entity and context classes from your database. Generally speaking, this is a one-time operation. Future updates to your entity classes are typically done manually.
For more information on this process, see this tutorial:
http://www.entityframeworktutorial.net/code-first/code-first-from-existing-database.aspx
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The last of the three
workflows to be added to EF,
0:00
the code first workflow takes yet
another point of view by allowing you to
0:02
define your model by directly writing the
code for your entity and context classes.
0:07
At runtime,
EF will generate our entity and
0:11
context classes and
in memory entity data model.
0:15
The code first workflow
allows you to define and
0:19
manipulate the data persistence for
your applications in a very natural way,
0:22
as you write the C# code for
the app itself.
0:27
Once you've defined your model, you can
then automatically generate the database
0:31
at run time or you can use a feature
called Code First Migrations to generate
0:35
the database and keep it in sync with your
model as it evolves and changes over time.
0:40
We'll cover Code First Migrations
in a later course.
0:45
The code first workflow is a natural
fit for a new application development.
0:49
With that being said, if you have
an existing database you can generate your
0:54
entity and context classes from your
database as a one time operation.
0:58
See in the teacher's notes for
more information.
1:03
In contrast to the database or model first
workflows, which can sometimes be tedious
1:06
to use, developers often find the code
first workflow to be fun to use.
1:11
In this course, we'll be using EF within
the context of a console application.
1:17
This will give us an easy way to test and
1:22
debug our EF code without having
to write a lot of unrelated code.
1:24
Then, in a later course,
1:29
we'll see how to integrate entity
framework with an ASP.NET NVC app.
1:31
Let's set up our project
in Visual Studio and
1:37
get started with using the code
first workflow to define our model.
1:39
>> Go ahead and
open the new project dialog and
1:44
select the Console Application
project template.
1:47
>> I'll name the project
ComicBookGalleryModel and update
1:53
the location to be a folder named src
within the repo that I created earlier.
1:58
Now we can use the NuGet package
manager to add EF to our project.
2:15
We don't even need to search for
the package.
2:22
It's the second most popular package
at the time of this recording
2:25
with 22.1 million downloads.
2:28
To install the package,
click the install button, then OK, and
2:33
accept the license In the Output window,
we can monitor the installation progress.
2:38
And it's finished now.
2:46
Let's add our entity class, but
first let's add a folder named
2:51
Models This folder will contain all
of our project's entity classes.
2:56
Right click on the folder,
and select, Add > Class.
3:06
Name the class, ComicBook and click Add.
3:12
I'll go ahead and make the class public.
3:22
There's no compelling reason at this
time to restrict access to this class.
3:26
And I'll add the following properties,
3:31
an int property named ID.
3:36
This property will contain a unique
value for each ComicBook in our system.
3:39
A string property named SeriesTitle.
3:46
Each ComicBook belongs to a series.
3:52
This property is the title of the series
that the ComicBook belongs to.
3:55
An int property named IssueNumber.
4:01
Within the series that
a comic book belongs to,
4:06
each issue has a unique number.
4:09
Issue one, issue two,
issue three, and so on.
4:11
A string property named Description.
4:17
This property is the description for
the comic book.
4:24
And a DateTime property named PublishedOn.
4:28
This property is the date that
the ComicBook was published on.
4:36
The code's first workflow uses a set
of conventions in order to know how
4:40
to interpret your entity classes and
4:45
generate the entity data
model that the EF will use.
4:47
For instance, the entity class name
will become the table name, either
4:51
the singular or plural version of the name
depending on how EF is configured.
4:56
And if the class contains a property named
Id, a primary key column with the same
5:02
name and data type will be added
to the entity's database table.
5:07
Because where using a numeric data type,
5:11
EF will also make the column
an identity column.
5:14
Identity columns are automatically
assigned values by the database
5:17
when new records are added to the table.
5:22
Primary key properties,
can also be named ID,
5:27
using upper case letters, the class name,
followed by Id, or the class name,
5:31
followed by ID, using upper case letters.
5:35
Any of these options will work fine.
5:44
Whichever one you or your team
decides to use just be consistent.
5:46
Now that we've seen how to create
an entity let's do a code challenge so
5:52
you can practice creating your own.
5:56
After that we'll add the context
class to our project.
5:58
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