Describe using migrations to Change the DB
this is where the code is the authoritative source of truth
.NET objects can be stored in a variety of DBs
including - postgresql, sql, azure cosmos
What is the entity model?
For the entity model, entity classes describing our entity model are built and may be stored in the models folder
The entities have primary key defined by [key] attribute
What is the required attribute in an entity model?
It can be null in the model but will not be stored/saved as a null
What is a navigation property?
A property defined in a C# entity class that holds a reference to related entities
Allows developers to traverse and manage relationships (like one-to-many or many-to-many) in an object-oriented manner.
What is a shadow property?
A shadow property in EF Core is a data field that exists in the database table and the EF Core model, but not in your C# entity class.
*Not present in the .NET class code.
How are shadow properties managed?
They are managed via the ChangeTracker API and are useful for auditing (e.g., LastUpdated) or foreign keys. They are configured in OnModelCreating using the Fluent API.
What is a DBContext object?
A DB Context object derives from dbcontext
the dbcontext object represents a DB session
What is EF Core migration?
EF Core migration creates a DB based on entities you have created in C#
Create by installing and adding in the terminal
What are the steps for EF Core migration?
Migration is created in VS, then you can run commands to update the database
EF migration history is created automatically to show what tables have been updated in the DB
What are the EF Core steps?
1 build entity classes
2. create a DBContext objects for the entities
3. Add fluent API or linq queries to the DB Context object
4. delete from DB when needed
Where do you create the add and save methods?
In the DBContext type object you created for your entity
Describe how to query tables in EF Core
Write queries to tables with fluent API or Linq
these use extension methods and lambda methods
What is the difference between extension methods and lambda methods?
Extension methods allow you to add methods to existing types (like IEnumerable<T>) without modifying the original type's source code.</T>
Lambda expressions are a concise syntax for defining an anonymous function (a function without a name) inline.
How do you scaffold code from existing DB?
Scaffolding uses EF core to work with an existing DB and reverse engineers it into entities in C#
Scaffolding treats the DB, not the code as the source of truth
What is the scaffold DB Context command?
by specifying the connection string and specifying the output directories for db context and models you can use scaffold command on the command line
Explain more about the scaffold command.
the -datadAnotation flag adds attributes to models when created / scaffolded from db
How do you keep business logic separate from scaffolded entities?
use partial classes or extension methods to keep business logic separate from the scaffolded entities
this helps ensure business logic doesn’t get overwritten when you re-scaffold the entities
What are some steps to use EF Core and .NET core to streamline dev?
1 in program.cs add razor pages and DB Context
2 .NET secrets manager store connection string for security
3 generate razor pages with CRUD in VS
select model and context class in VS UI
creates default CRUD pages automatically (*.cshtml)
includes ui input constraints/validation that matches constraints in the model
what is the start working directory element in the *.csproj file?
It tells .net core where to start
How do you specify a DB provider in EF Core?
Change build options depending on which DB provider you use
How does EF Core keep track of changes?
The migrations folder contains changes made to entities and db
What are the primary keys in EF Core?
EF Core auto generates primary key from an int 32 in the entity
Uniquely identifies an entity
How do you optimize performance in EF Core?
disable changetracking for read only queries by
adding .AsNoTracking() method to the query
.assplitquery() split querys into multiple for better perf
What is eager loading and lazy loading?
eager loading -
lazy loading
cartesian explosion bad for performance
