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Let's look at the options for changing the name of the generated database.
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cd dotnet-comic-book-gallery-model
git checkout tags/v2.3 -b changing-the-database-name
Code
Here's the database connection string to connect to the default SQL Server LocalDB instance and set the generated database name to "ComicBookGallery".
Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=ComicBookGallery;Integrated Security=True;MultipleActiveResultSets=True
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Before we look at the options for
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changing the database name,
let's delete our current database.
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Deleting a database is not an operation
that you'll do very often,
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especially given that deleting a database
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means that you'll forever lose access
to the data contained within it.
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Since our database is being
generated by our app, and
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it doesn't contain any data that
we need to keep, it's safe to do.
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We can delete our database
by right-clicking here,
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on the database in the SQL Server
Object Explorer, and selecting Delete.
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We'll be asked if we also
want to delete the backup and
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restore history information, and
close any existing connections.
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Be sure to check both options, that'll
ensure that the delete operation will
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succeed, even if we currently have
an open connection to the database.
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We're going to look at three options for
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changing the name of
the generated database.
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The first and easiest of these options is
to add a constructor to our context class.
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And call the base class constructor
that accepts a parameter for
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the database name or connection string.
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Public Context() then colon
followed by the base keyword,
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which allows us to call
the members in the base class.
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In this case, the base class constructor.
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We'll take a look at how to use the
connection string option in just a moment.
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For now I'll just pass in
the name of the database that
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I'd like to use, ComicBookGallery.
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Now let's run the app Press Enter
to continue execution.
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Then refresh the list of databases in
the SQL Server Object Explorer window,
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and we'll see our new
ComicBookGallery database.
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The DbContext base class
constructor that we're calling
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also accepts the database
connection string.
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This is our second option for
changing the name of the database.
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Here in Notepad, I have an example of
a SQL Server database connection string.
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The Data Source value is the name of the
database server that we want to connect
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to, which is a localdb
instance named MSSQLLocalDB.
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If we wanted to use a different
database server other than localdb, or
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a differently named instance,
we could change this value.
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The Initial Catalog value is
the name of the database.
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The Integrated Security value
indicates that we want to use
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Windows authentication.
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And the MultipleActiveResultSets value
indicates that we want to be able to run
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more than one SQL batch on an open
connection at the same time.
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Setting this value to true,
generally speaking,
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helps to improve the overall performance
of retrieving data from the database.
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For more information about
multiple active result sets, or
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MARS, see the teacher's notes.
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I'll copy and paste the connection string
to the base class constructor method call.
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Because our connection string contains a
backslash, which is used to escape special
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characters and text, we need to add
another backslash before our backslash.
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This tells the compiler that we
actually want a backslash character, or
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we can leave the single backslash and
add an at sign before the starting quote.
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This tells the compiler to treat our
text as a verbatim string literal and
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ignore any escape sequences
contained within the text.
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Let's also add the text ConnectionString
as a suffix to the initial catalog name so
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we don't have to delete
our existing database.
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Run the app again, and
press Enter to continue execution.
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Refresh the list of databases, and
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we'll see our new
ComicBookGalleryConnectionString database.
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The third and last option for
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changing the name of the database is to
add a database connection string whose
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name matches the name of our context
class to our apps configuration file.
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For console apps,
we'll use the App.config file
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in the root our project to add
the necessary configuration.
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For ASP.NET MVC apps,
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you can use the web.config file
in the root of the project.
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We'll be covering how to use Entity
Framework within MVC apps in another
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course.
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We start by adding a connectionStrings
element right underneath
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the root configuration element.
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And within that element,
we'll add an add element.
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On the add element,
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we'll add a name attribute whose value
will match the name of our context class.
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That's how EF will know to associate
this connection string with our context.
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Then we'll add a connection string
attribute for our connection string,
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which I'll cut and
paste from the context class.
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I'll also change the database
name suffix to AppConfig.
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Lastly, we'll add a providerName attribute
to indicate which data provider to use.
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Since we're using a SQL Server
localdb database,
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I'll set the value to
System.Data.SqlClient.
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Now that we have our connection string
defined in the App.config file,
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we can remove the constructor
from the context class.
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Run the app again, and
press Enter to continue execution.
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Refresh the list of databases, and
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we'll see our new
ComicBookGalleryAppConfig database.
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Of the three options that we just saw,
I like the third option, as it keeps
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the configuration of our database
location and name out of our code.
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That makes it possible to
change the location or
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name of the database without
having to rewrite our code.
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Which is especially helpful
when deployment applications
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into other environments.
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Let's remove the AppConfig suffix from the
database name in the connectionString, so
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our database name is
just ComicBookGallery.
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Then I'll do some cleanup and
delete all of the existing databases.
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Lastly, I'll run the app one more time,
and
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verify that our database
is successfully created.
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Refresh the list of databases, And
here's our ComicBookGallery database.
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