Entity Framework Core 7

Links

• What's New in EF Core 7.0
• Entity Framework Plus
• linq2db

Entity Framework Core Tools

.NET Core CLI

# test if Entity Framework Core Tools has been installed dotnet ef # be sure to run the previous command in the folder of the project where EF has been added # dotnet ef must be installed as a global or local tool dotnet tool install --global dotnet-ef # installed in ~/.dotnet/tools # Add ~/.dotnet/tools to PATH # update dotnet tool update dotnet-ef --global # --version 7.0.14

Package Manager Console in Visual Studio

Visual Studio View → Other Windows → Package Manager Console Default Project = the one containing the entity configurations Startup Project = the one containing the sql server configuration

# test if Entity Framework Core Tools has been installed Get-Help about_EntityFrameworkCore # install Install-Package Microsoft.EntityFrameworkCore.Tools # update Update-Package Microsoft.EntityFrameworkCore.Tools

Add Entity Framework Core package

# sql server dotnet add package Microsoft.EntityFrameworkCore.SqlServer # mysql dotnet add package Pomelo.EntityFrameworkCore.MySql

Microsoft.EntityFrameworkCore.Design allows to scaffold and has to be installed on the executed project.

Data Providers

Provider	Package NuGet	Connection String
SQL Server	Microsoft.EntityFrameworkCore.SqlServer	Server=(localdb)\\MSSQLLocalDB;Database=MyDb;Integrated Security=True;MultipleActiveResultSets=True; Server=localhost;Database=MyDb;User=sa;Password=pwd;
MySQL / MariaDB	Pomelo.EntityFrameworkCore.MySql	server=localhost;database=MyDb;user=root;password=pwd
PostgreSQL	Npgsql.EntityFrameworkCore.PostgreSQL	Host=localhost;Database=MyDb;Username=root;Password=pwd
InMemory	Microsoft.EntityFrameworkCore.InMemory	databaseName: "test_database"
Sqlite	Microsoft.EntityFrameworkCore.Sqlite	Data Source=/tmp/file.db

Connection string

• The connection string could be stored in the secret store in dev environnement
• It could also be stored in appsettings.Development.json in dev environnement

appsettings.json

{ "ConnectionStrings": { "MariaDb": "server=localhost;database=test;user=test;password=***" } }

Dependency injection (ASP.Net Core)

By default the DbContext is registered as a scoped service: a new DbContext is created on a new thread for each API request.

MariaDb / MySql

Program.cs

var connectionString = builder.Configuration.GetConnectionString("MariaDb"); // get the connection string from the appsettings.json or the secret store var serverVersion = new MariaDbServerVersion(new Version(10, 11, 4)); builder.Services.AddDbContext<MyAppContext>( dbContextOptions => dbContextOptions .UseMySql(connectionString, serverVersion));

• MySQL .NET Connection String Options

SSL Authentication Error

On Windows, if named pipe authentication is used you may have this issue.
Disable SSL in the connection string to workaround it: sslmode=none

SQL Server

SqlConnectionStringBuilder

Program.cs

var connectionStringWithoutPassword = builder.Configuration.GetConnectionString("SqlServer"); var connectionStringBuilder = new SqlConnectionStringBuilder(connectionStringWithoutPassword); // Package: System.Data.SqlClient connectionStringBuilder.Password = builder.Configuration["SqlServerPassword"]; var connectionString = connectionStringBuilder.ConnectionString;

DbContext OnConfiguring

DataAccess/MyAppContext.cs

public class MyAppContext : DbContext { protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { optionsBuilder.UseSqlServer("server=localhost;database=test;user=test;password=***"); // hard-coded connection string optionsBuilder.UseMySql("name=ConnectionStrings:MariaDb", ServerVersion.Parse("10.11.4-mariadb")); // get it from the appsettings.json or the secret storage optionsBuilder.UseSqlServer(ConfigurationManager.ConnectionStrings["SqlServerConnectionString"].ConnectionString); // WPF

Log underlying SQL query

Program.cs

builder.Services.AddDbContext<AppContext>( options => options .LogTo(Console.WriteLine, LogLevel.Information) // simple logging .UseLoggerFactory(LoggerFactory.Create(loggingBuilder => loggingBuilder .AddConfiguration(builder.Configuration.GetSection("Logging")) // log the configuration .AddConsole() // log into the console if there is one .AddDebug())) // log into VS output Window and Linux journal .EnableSensitiveDataLogging( // include the values of data in exception messages builder.Configuration.GetValue<bool>("DbContextLogOptions:EnableSensitiveDataLogging", false)) .EnableDetailedErrors( // wrap each call to read a value in a try-catch block builder.Configuration.GetValue<bool>("DbContextLogOptions:EnableDetailedErrors", false)) .UseMySql(connectionString, serverVersion) );

appsettings.json

"DbContextLogOptions": { "EnableSensitiveDataLogging": true, "EnableDetailedErrors": true },

Database first: scaffold database to model entities

# generate entity classes and context class dotnet ef dbcontext scaffold "Server=localhost;Database=MyDb;User=sa;Password=***;" # an harcoded connection string "Name=ConnectionStrings:SqlServer" # get the connection string from the appsettings.json or the secret storage Microsoft.EntityFrameworkCore.SqlServer # the database provider --output-dir DataAccess/Entities # output folder for entities --context-dir DataAccess # output folder for DbContext --context "MyDbContext" # default context name: DbNameContext --force # overwrite all the class files --table table1 --table table2 # scaffold only table1 and table2

Visual Studio

• Ensure Entity Framework Core Tools have been installed
• View → Other Windows → Package Manager Console
• Default Project = the one containing the entity configurations ?
• Startup Project = the one containing the sql server configuration ?

Scaffold-DbContext 'Data Source=MY-PC;Initial Catalog=MyDb' Microsoft.EntityFrameworkCore.SqlServer -OutputDir Entities

Error	Titre colonne 2
The certificate chain was issued by an authority that is not trusted	Add Encrypt=False to the connection string
Login failed for user	Add Integrated Security=True to the connection string

Repository Pattern

• 1 Repository per resource: ItemRepository
• 1 DbContext for the whole application

Repositories/ItemRepository.cs

public class ItemRepository : IItemRepository { private readonly MyAppContext context; public ItemRepository(MyAppContext context) { this.context = context; } public async Task<IReadOnlyCollection<Item>> GetAllItemsAsync(CancellationToken cancellationToken) { var items = await context.Items .Include(x => x.NavigationProperty) .AsNoTracking() .ToListAsync(cancellationToken); return items; } public async Task<Item?> GetItemByIdAsync(int id, CancellationToken cancellationToken) { var item = await context.Items .AsNoTracking() .SingleOrDefaultAsync(x => x.Id == id, cancellationToken); return item; } public async Task<IReadOnlyCollection<Item>> GetItemsByNameAsync(string name, CancellationToken cancellationToken) { var items = await context.Items .Where(x => EF.Functions.Like(x.Name, $"%{name}%")) .AsNoTracking() .ToListAsync(cancellationToken); return items; } public async Task<Item> CreateItemAsync(Item item, CancellationToken cancellationToken) { await context.AddAsync(item, cancellationToken); await context.SaveChangesAsync(cancellationToken); return item; // it now contains its id } public async Task<bool> UpdateItemAsync(int id, Item item, CancellationToken cancellationToken) { ArgumentNullException.ThrowIfNull(item); var itemToUpdate = await context.Items.SingleOrDefaultAsync(x => x.Id == id, cancellationToken); if (itemToUpdate is null) { return false; // send not found from controller then } itemToUpdate.Name = item.Name; await context.SaveChangesAsync(); return true; } public async Task<bool> DeleteItemAsync(int id, CancellationToken cancellationToken) { var nbAffectedRows = await context.Items.Where(x => x.Id == id).ExecuteDeleteAsync(cancellationToken); return nbAffectedRows == 1; }

Generic repository

RepositoryBase.cs

public abstract class RepositoryBase<TEntity, TCreateUpdateQuery> where TEntity : class, new() { private readonly AppContext context; private DbSet<TEntity> dbEntities { get; } protected RepositoryBase(BourseContext context) { this.context = context ?? throw new ArgumentNullException(nameof(context)); dbEntities = this.context.Set<TEntity>(); } protected async Task<IReadOnlyCollection<TResult>> GetAsync<TResult>( Expression<Func<TEntity, TResult>> selector, Func<IQueryable<TEntity>, IIncludableQueryable<TEntity, object>>? include = null, Expression<Func<TEntity, bool>>? predicate = null, Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>>? orderBy = null, Func<IQueryable<TEntity>, IQueryable<TEntity>>? skipTake = null, bool disableTracking = true, CancellationToken cancellationToken = default) where TResult : class { IQueryable<TEntity> query = dbEntities; if (include is not null) { query = include(query); } if (predicate is not null) { query = query.Where(predicate); } if (orderBy is not null) { query = orderBy(query); } if (skipTake is not null) { query = skipTake(query); } if (disableTracking) { query = query.AsNoTracking(); } return await query.Select(selector).ToListAsync(cancellationToken); } public async Task<TEntity> CreateAsync( TEntity entity, CancellationToken cancellationToken) { ArgumentNullException.ThrowIfNull(entity); await context.AddAsync(entity, cancellationToken); await context.SaveChangesAsync(cancellationToken); return entity; } public async Task<bool> UpdateAsync( Expression<Func<TEntity, bool>> filterByIdExpression, TCreateUpdateQuery query, CancellationToken cancellationToken) { ArgumentNullException.ThrowIfNull(query); var entityToUpdate = await dbEntities .FirstOrDefaultAsync(filterByIdExpression, cancellationToken); if (entityToUpdate is null) { return false; } UpdateEntityFromCreateUpdateQuery(query, entityToUpdate); await context.SaveChangesAsync(cancellationToken); return true; } public async Task<bool> DeleteAsync( Expression<Func<TEntity, bool>> filterByIdExpression, CancellationToken cancellationToken) { var nbAffectedRows = await dbEntities .Where(filterByIdExpression) .ExecuteDeleteAsync(cancellationToken); return nbAffectedRows > 0; } }

Avoid using AsNoTracking and Include

AsNoTracking is used to improve performances when you don't need the entities to be tracked for changes. But a better way to improve performances is to use projection so you don't return the whole entity but only the needed fields. This way you don't need AsNoTracking because there is no more entities to track.
Include is used to retrieve other entities linked by a foreign key / navigation property. If you use a projection with a navigation property, you don't have to use Include.

Query generation

string contains vs like

context.Items.Where(x => x.Name.Contains("item1"));

SELECT [i].[Id], [i].[Name] FROM [Items] AS [i] WHERE (@__query_Name_0 LIKE N'') OR (CHARINDEX(@__query_Name_0, [i].[Name]) > 0)

context.Items.Where(x => EF.Functions.Like(x.Name, "%item1%"));

SELECT [i].[Id], [i].[Name] FROM [Items] AS [i] WHERE [i].[Name] LIKE @__Format_1

any

context.Items.Any(x => x.Id == 1);

SELECT EXISTS ( SELECT 1 FROM `item` AS `i` WHERE `i`.`id` = @__id_0)

left join

• Perform left outer joins

// with navigation property context.Users.Select(u => new { u.Name, u.Group?.Name }); // method syntax context.Users .GroupJoin( context.Groups, user => user.GroupId, group => group.Id, (user, grouping) => new { user, grouping } ) .SelectMany(z => z.grouping.DefaultIfEmpty(), (z, grp) => new { userName = z.user.Name, groupName = grp.Name }) .Select(x => new { x.userName, x.groupName }); // query syntax from user in context.Users join group in context.Groups on user.GroupId equals group.Id into grouping from grp in grouping.DefaultIfEmpty() select new { userName = user.Name, groupName = grp.Name };

SELECT u.Name AS userName, g.Name AS groupName FROM User AS u LEFT JOIN Group AS g ON u.GroupId = g.Id

Pagination

public async Task<IReadOnlyCollection<Item>> GetItemsAsync(ItemQuery query, CancellationToken cancellationToken) { var items = await this.context.Items .Skip((query.PageIndex - 1) * query.PageSize) .Take(query.PageSize) .AsNoTracking() .ToListAsync(cancellationToken); return items; }

What's New in EF Core 7.0

Bulk delete

await context.Tags.Where(t => t.Text.Contains(".NET")).ExecuteDeleteAsync();

DELETE FROM [t] FROM [Tags] AS [t] WHERE [t].[Text] LIKE N'%.NET%'

Bulk update

await context.Posts .Where(p => p.PublishedOn.Year < 2022) .ExecuteUpdateAsync(s => s .SetProperty(b => b.Title, b => b.Title + " (" + b.PublishedOn.Year + ")") .SetProperty(b => b.Content, b => b.Content + " ( This content was published in " + b.PublishedOn.Year + ")"));

UPDATE [p] SET [p].[Content] = (([p].[Content] + N' ( This content was published in ') + COALESCE(CAST(DATEPART(year, [p].[PublishedOn]) AS nvarchar(max)), N'')) + N')', [p].[Title] = (([p].[Title] + N' (') + COALESCE(CAST(DATEPART(year, [p].[PublishedOn]) AS nvarchar(max)), N'')) + N')' FROM [Posts] AS [p] WHERE DATEPART(year, [p].[PublishedOn]) < 2022