- 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
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Workflows: Database First
6:19The process of defining your model and connecting to a database—either existing or new—is referred to as a "workflow". Let's start with an overview of the Database First workflow.
To get started with using entity
framework, you need to do two things.
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Describe the shape of your data,
and connect to a database.
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Describing the shape of the data is
often referred to as data modeling.
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When data modeling, you define the
entities, properties on those entities,
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and the relationships between entities.
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For example, in our fitness frog web app
from an earlier course, we modeled workout
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data using classes that stored
things like the type of activity and
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how long it lasted.
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The data model in EF terminology is
known as, the entity data model,
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or EDM, or just the model.
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EF provides a visual designer
that allows you to visualize and
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in some cases edit your model.
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We'll see the designer in just a moment.
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If you have an existing database,
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you can use it as a starting
point when defining your model.
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If you don't have a database,
you can use EF to generate the database.
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The process of defining your model and
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connect it to a database either existing
or new is referred to as a workflow.
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EF supports three workflows,
Database First, when
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you want to generate your model and entity classes from an existing database.
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Model First when you don't
have an existing database and
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you want to define your model
using the visual designer and
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allow EF to generate your entity classes and database.
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And Code First which
forgoes the visual designer
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by allowing you to define your model by
writing the code for your entity classes.
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In this course will be using the most
popular of these three options,
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the code first workflow.
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But let's start with an overview of the
database first and model first workflows
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so you'll understand at a high level
how they compare to each other and
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to the code first workflow.
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Database First workflow was originally
the only workflow that EF supported.
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As some name suggests this workflow
starts with an existing database.
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After connecting to the database EF
generates the model from the database.
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Then the entity and context classes
are generated from the model.
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With the Database First workflow,
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changes that need to be made to
the model start in the database
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by making schema changes and flow to the application's entity data model.
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This means that the model from the
application side is effectively read only.
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I'm going to walk through
the steps of creating a model
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using the database first workflow.
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This will be a quick overview.
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So don't worry if you see something
that doesn't make complete sense.
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After the next video, we'll be
focusing on the Code First workflow
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which I'll explain in detail
throughout this course.
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To get started with this workflow, we add
in Ado.net into enity data model item
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to our project which will drop us
into the Enity Data Model wizard.
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To start, we're asked what the model
should contain and were presented with
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four options Entity Designer from
database, Empty EF Designer Model,
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Empty Code First model and
Code First from database.
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The last two options are for
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the code first workflow which we'll
discuss later in the section.
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The second option is for
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the model first workflow which we'll
take a look at in the next video.
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And the first option is for
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the database first workflow which is
the one that we want for this video.
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The second step allows us to
choose our data connection.
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I don't have any existing data connections
so I'll create a new connection.
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First, I need to provide the name for
my database server.
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I'm using SQL Server local DB, so
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my database server name
will start with (localDB),
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followed by a backslash,
followed by MSSQLLocalDB.
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In the next section, we'll be taking
a closer look at how to install,
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configure and use SQL Server Local DB.
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Now I'll select the database
that I want to use.
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DatabaseFirstTestDB, and click OK.
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Now that we've defined our
data connection, click Next.
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In the last step, we can select the
database objects to include in our model.
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I'll click on the box to the left of the
tables item to select all the database's
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tables.
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Click Finish to complete the wizard.
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Now we have an EDMX file in our project.
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Underneath EDMX file we have
to code generation templates
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one used to automatically
generate the code for
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the indie classes and another to
generate the code for the context class.
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We'll take a closer look at the entity and
context classes later in the section.
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Code generation templates contain code
that generates or writes other code.
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Using code generation to automate the
creation of our entity in context classes
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saves us the manual effort
creating those classes ourselves.
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When the database schema is updated
we can regenerate the EDMX file.
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We can do this by right clicking anywhere
in the empty space in the designer and
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selecting update model from database.
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This opens a dialog that will show us
a list of the database objects that we can
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add along with the objects that
need to be refreshed or deleted.
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Because the database first workflow
requires you to start with an existing
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database.
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It's a natural fit when you're updating
an existing application to use EF.
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For new applications development
developers like having the option to start
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with defining their model
from within the application.
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The model first workflow was created for
this purpose.
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Up next we'll see how we can use the model
first workflow to not only generate
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the entity and context classes from
the model but also the database.
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