Entity Framework Core Tools

# 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 --global dotnet-ef

Add Entity Framework Core package

# sql server
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Design

# mysql
dotnet add package Pomelo.EntityFrameworkCore.MySql
dotnet add package Microsoft.EntityFrameworkCore.Design

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

Configuration file and secrets

appsettings.json

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

Dependency injection (ASP.Net Core)

MariaDb / MySql

Program.cs

var connectionString = builder.Configuration.GetConnectionString("MariaDb");
var serverVersion = new MariaDbServerVersion(new Version(10, 11, 4));

builder.Services.AddDbContext<MyAppContext>(
    dbContextOptions => dbContextOptions
        .UseMySql(connectionString, serverVersion)
        // TODO The following three options help with debugging, but should be changed or removed for production.
        .LogTo(Console.WriteLine, LogLevel.Information)
        .EnableSensitiveDataLogging()
        .EnableDetailedErrors());

SQL Server

Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    // SQL Server
    var builder = new SqlConnectionStringBuilder(Configuration.GetConnectionString("SqlServer")); // read the appsettings.json
    builder.Password = Configuration["DbPassword"]; // use the Secret Manager in dev, and an environment variable in prod
    services.AddDbContext<MyAppContext>(options =>
        options.UseSqlServer(builder.ConnectionString)
    );

    // MySql
    services.AddDbContext<MyAppContext>(options =>
        options.UseMySql(
            Configuration.GetConnectionString("MySql"),
            mySqlOptions => mySqlOptions.ServerVersion(
                new ServerVersion(new Version(10, 5, 8),
                ServerType.MariaDb)));
            // mySqlOptions => mySqlOptions.ServerVersion("10.5.8-mariadb");
    );

    // In Memory
    services.AddDbContext<MyAppContext>(options =>
        options.UseInMemoryDatabase("WebApplicationCoreMemoryDb");
    );

DataAccess/MyAppContext.cs

public class MyAppContext : DbContext
{
    // permet de passer des options à la construction du DbContext
    public MyAppContext(DbContextOptions<MyAppContext> options) : base(options)
    { }

MyController.cs

public class MyController
{
    private readonly MyAppContext context;

    public MyController(MyAppContext context)
    {
        this.context = context;
    }

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")); // connection string in the appsettings.json
        optionsBuilder.UseSqlServer(ConfigurationManager.ConnectionStrings["SqlServerConnectionString"].ConnectionString); // WPF

Constructor parameter

var builder = new ConfigurationBuilder()
    .AddUserSecrets<MyAppContextFactory>();
var configuration = builder.Build();

var connectionStringBuilder = new SqlConnectionStringBuilder("server=localhost;database=test;user=test;");
connectionStringBuilder.Password = configuration["DbPassword"];

var connectionString = connectionStringBuilder.ConnectionString;
var connectionString = "server=localhost;database=test;user=test;password=****";

var contextOptions = new DbContextOptionsBuilder<MyAppContext>()
    .UseMySql(
        connectionString,
        mySqlOptions => mySqlOptions.ServerVersion("10.5.8-mariadb"))
    .Options;

using var context = new MyAppContext(contextOptions);

DataAccess/MyAppContext.cs

public class MyAppContext : DbContext
{
    public MyAppContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    { }

Design time DbContext factory

Explain how to create a Context which doesn't have a parameterless ctor.
Separate the EF code needed for generating database tables at design-time from EF code used by your application at runtime.

DataAccess/MyAppContextFactory

public class MyAppContextFactory : IDesignTimeDbContextFactory<MyAppContext>
{
    private string connectionString;

    public MyAppContextFactory()
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json")
            .AddUserSecrets<MyAppContextFactory>();  // read stored secrets
        var configuration = builder.Build();

        connectionString = configuration.GetConnectionString("SqlServer");
    }

    public MyAppContext CreateDbContext(string[] args)
    {
        var builder = new DbContextOptionsBuilder<MyAppContext>();
        builder.UseSqlServer(connectionString);
        var dbContext = new MyAppContext(builder.Options);
        return dbContext;
    }
}

DataAccess/MyAppContext.cs

public class MyAppContext : DbContext
{
    // permet de passer des options à la construction du DbContext
    public MyAppContext(DbContextOptions<MyAppContext> options) : base(options)
    { }

var dbContextFactory = new MyAppContextFactory();
using var dbContext = dbContextFactory.CreateDbContext(args);