- Welcome to Entity Framework Basics 2:37
- What is Entity Framework? 4:19
- Entity Framework Review 5 questions
- Workflows: Database First 6:19
- Workflows: Model First 5:50
- Adding Our First Entity Using the Code First Workflow 6:02
- Adding an Entity 2 objectives
- Adding Our Context 3:03
- Adding a Context 2 objectives
- Using the Context 5:03
- Section Review 10 questions
Preview
Video Player
00:00
00:00
Adding Our Context
3:03Let's add a context class to our project, so we can persist and retrieve data from our database.
Before we can persist and
0:00
retrieve data from our database, we need
to add a context class to our project.
0:01
The context class is our
gateway to the database.
0:06
All communication from our application to
the database flows through the context.
0:09
The context defines
the available Entity sets and
0:14
manages the relationships
between those entities.
0:17
It's used to retrieve entities
from the database, persist new and
0:21
changed entities to the database, and
even to remove entities from the database.
0:25
When retrieving entities from the
database, the context is responsible for
0:30
materializing the data from the database
into Entity Object Instances.
0:34
The context also caches those entity
object instances for its lifetime, however
0:39
short or long that might be so that it
can track changes to those entities.
0:44
As we learn about EF and
develop our projects,
0:50
we'll interact with the context again and
again.
0:52
Let's see how to add a context
class to our project.
0:56
Right-click on the project and
select Add > Class.
0:59
Name the class Context and click Add.
1:05
Just like we did with the entity class, go
ahead and add the public access modifier.
1:11
Then inherit from the EF DbContext class.
1:17
Visual Studio will complain
that it can't find the type.
1:23
So go ahead and
add the missing using statement for
1:26
the System.Data.Entity namespace.
1:29
The DbContext class is a higher level
abstraction of EF's object context class.
1:34
before the DbContext
class was added to EF,
1:40
object context was used to load and
persist entities.
1:44
While object context isn't deprecated,
1:48
it's almost never used directly now
that we have the DbContext class.
1:51
Given that, we'll focus on learning
how to use the DbContext class.
1:56
Our context class needs to contain
a collection of Db set properties.
2:00
One property for each indie that
we need to write queries for.
2:05
Let's add a Db set property for
the ComicBook entity.
2:09
Public DbSet of type ComicBook.
2:14
Add the missing namespace, or
ComicBookGalleryModel.Models, and
2:20
use the plural version of our entity class
name for the property name, ComicBooks.
2:27
While not necessary, using the plural
version of the entity class name
2:34
is a common convention for
DB set property names.
2:37
Often, you'll add a DB set property for
2:41
each entity class that
you have in your model.
2:43
But sometimes you won't need to add
a DB set property for an entity.
2:46
We'll see an example of
that later in this course.
2:50
For now, this is all of the code that
our context class needs to contain.
2:53
Next, we'll update our
console app to persist and
2:57
retrieve data using our context.
3:00