- What are Migrations? 4:41
- Enabling Migrations 6:06
- Code First Migrations Review 5 questions
- The Configuration Class 2:09
- Adding Our First Migration 4:05
- The Migration Fluent API 6:04
- Updating the Database 4:13
- Populating Our Database with Seed Data 7:31
- Using the Configuration Class to Add Seed Data 1 objective
- Excluding Test Data in Production 5:54
- Using a Preprocessor Directive to Exclude Test Data 1 objective
- Section Review 10 questions
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Adding Our First Migration
4:05Now that we've enabled migrations in our project, let's add our first or initial migration.
Now that we've enabled migrations in
our project, let's add our first or
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initial migration.
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If it's not already open, go ahead and
open the NuGet package manager console.
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From the top menu its Tools > NuGet
Package Manager > Package Manager Console.
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To add a migration, type add migration
followed by the name we want to use for
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the migration.
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Add-Migration space Initial.
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I like to name my first migration
initial but this isn't a requirement.
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You can use whatever
name you'd like to use.
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Press enter to run the command.
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Once the command is completed,
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we can see that EF added a file to
the migrations folder named initial.
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Prefixed with a time stamp
value representing the date and
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time when we created the migration.
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The time stamp is in coordinated
universal time or UTC.
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UTC is the primary time standard by which
the world regulates clocks and times.
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See the teacher's notes for
more information.
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Prefix in the migrations
file name with a time stamp
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ensures that our migration files
will display in chronological order.
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That makes it easy to identify
the order that they were created in.
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When the command completed, it displayed
a message in the package manager console
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highlighted here in yellow.
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The designer code for
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this migration file includes a snapshot
of your current code first model.
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This snapshot is used to calculate
the changes to your model
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when you scaffold the next migration.
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Designer code is code that is
generated by Visual Studio or
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other tools running inside a Visual Studio
like code first migrations
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to help support functionality
within those tools.
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Designer code files ends with
the suffix dot designer.
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Visual Studio recognizes
this naming convention and
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will nest these files underneath
the associated code file.
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The snapshot of our current model
isn't located within the code file but
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rather in associated resource file.
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Resource files contain application
data stored as name value pairs.
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If we double click the file, Visual Studio
will display the resource data in a grid.
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The Target value is a snapshot
of the entity data model
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that was used to create the migration.
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The decider code file and
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the associated resource file, is a code
first migrations implementation detail.
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And not something that you
typically find useful to review.
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Now, let's take a look
at the migration itself.
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Notice that the class
name is just Initial,
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without the time stamp prefix that's
included in the code filename.
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This is one of the rare times where the
standard convention of the code filename
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matching the class name is not followed.
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The partial keyword indicates that
the Initial class is a partial class.
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Partial classes, allow you to split
the definition for a class across one or
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more files.
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The other part of our Initial class is
located within the designer code file.
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Our class inherits from the code first
migrations DbMigration base class and
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overrides the up and down methods.
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The Up method contains code
to update the database to
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be in sync with the model that was
used to generate this migration.
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You can think of this method as being
responsible for upgrading the database.
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The Down method contains code to
remove the updates that were applied
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in the Up method.
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So that the database will be in sync
with the previous version of the model.
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You can think of this method as being
responsible for downgrading the database.
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