5.4 KiB
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
Show migration status (Get-Migration has more details):
dotnet ef migrations list --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.
Remove last migration:
dotnet ef migrations remove --startup-project ./ --project ../EntityFrameworkCore.Data
Create migration script (This generates SQL of all the migrations). Add the --idempotent parameter to make it idempotent. This applies only the changes not already made. You can also specify migration names to only generate between specific migrations.
dotnet ef migrations script --startup-project ./ --project ../EntityFrameworkCore.Data
Rollback to specific migration, use list command to see (Pending) changes:
dotnet ef database update 20250406180432_AddMatchAndLeagueEntities --startup-project ./ --project ../EntityFrameworkCore.Data
To re-apply changes again, simply do a database update again. Beware that data will be lost.
Links
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
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.
Database
Relationships
- A League has one or more Teams (1:M)
- A Team has one Coach (1:1)
- Matches are played by many Teams (M:M)