Entity Framework - Dead Ball Zone

This is a practice project to learn Entity Framework.

Using the 1998 game Dead Ball Zone for inspiration.

.NET commands:

NuGet commands

Install Entity Framework Core NuGet package:

dotnet add package Microsoft.EntityFrameworkCore --version 9.0.3

Creation commands

To list all available templates:

dotnet new -l

New class:

dotnet new class -n MyClass

adding to an existing solution:

dotnet sln add Data/Data.csproj

Entity Framework commands

Create a migration, inside of the Console project, referring to the Data project:

dotnet ef migrations add InitialMigration --startup-project ./ --project ../EntityFrameworkCore.Data

Update the database:

dotnet ef database update --startup-project ./ --project ../EntityFrameworkCore.Data

Database-first scaffolding example: (no need for escape slashes)

Scaffold-DbContext 'connection-string' Microsoft.EntityFrameworkCore.SqlServer -ContextDir ScaffoldDbContext -OutputDir ScallfoldModels

dotnet ef dbcontext scaffold "connection-string" Microsoft.EntityFrameworkCore.SqlServer --context-dir ScaffoldDbContext --output-dir ScaffoldModels --startup-project ./ --project ..\EntityFrameworkCore.Data\

Using -force parameter to force overrides when scaffolding.

Links

• Entity Framework - Database providers

Terms

A database-context is an abstraction of the database structure in code.

• It lists the models and their database table names.
• It instantiates a database connection during the runtime of the application.
• Allows configurations to be made in code.

The migrations provide a version-controlled method to maintain the state of the database.

• It is possible to track when, and by who changes were made.
• In the Up method, it is described which changes should be made.
• in the Down method, it is described which changes should be undone. This allows rollback.
• There is a history table that is kept by default to track migrations.

Installed NuGet packages

A list of installed NuGet packages in this application.

Note that the Microsoft.EntityFrameworkCore.Tools is used for Powershell commands used in the Package Manager Console for Visual Studio and that Microsoft.EntityFrameworkCore.Design is used for cross-platform command tools.

Console project

Microsoft.EntityFrameworkCore.Tools

• dotnet add package Microsoft.EntityFrameworkCore.Tools --version 9.0.3

Data project

Microsoft.EntityFrameworkCore

• dotnet add package Microsoft.EntityFrameworkCore --version 9.0.3

Microsoft.EntityFrameworkCore.Sqlite

• dotnet add package Microsoft.EntityFrameworkCore.Sqlite --version 9.0.3

Tips for efficient querying

• Use indexes.
• Use projections.
• Limit result set (skip and take)
• Use async calls.
• Use FromSQLRaw() for an optimized query if it gets complex in LINQ.
• Use no-tracking.
• Use batch operations.

Tracking

Tracking works best when the same DbContext is used for both querying and changing entities. EF Core automatically tracks the state of the queried entities and detects any changes made, until SaveChanges() is called, which is a method to save pending changes to the database. These changes are detected with the DetectChanges() function. This function can be manually called, to see what the changes are, but it is automatically called by the SaveChanges() function. SaveChanges() is transactional (for most providers).

The following states are tracked in the EntityState.State property:

• Detached: entity is not tracked.
• Added: new entity, not yet added to the database.
• Unchanged: no changes to the entity.
• Modified: changes are made to the entity.
• Deleted: the entity is in the database, but is marked for deletion.

The Find functions require tracking, instead, use the First function, with a lambda for the ID.