In this article, you will see EF Core's improvements to SQLite, In-memory providers, and the EF.Functions.Contains method.
This is the fourth article in a summary of the new features of EF Core 6:
1 SQLite supports DateOnly and TimeOnly
在 EF Core 6.0 中，SQLite 提供者支持新的 DateOnly 和 TimeOnly 类型。它将它们存储为 TEXT。
using var context = new ExampleContext();
var query1 = context.People
.Where(p => p.Birthday < new DateOnly(2000, 1, 1))
.ToQueryString();
Console.WriteLine(query1);
// SELECT "p"."Id", "p"."Birthday", "p"."Name"
// FROM "People" AS "p"
// WHERE "p"."Birthday" < '2000-01-01'
var query2 = context.Notifications
.Where(n => n.AllowedFrom >= new TimeOnly(8, 0) && n.AllowedTo <= new TimeOnly(16, 0))
.ToQueryString();
Console.WriteLine(query2);
// SELECT "n"."Id", "n"."AllowedFrom", "n"."AllowedTo"
// FROM "Notifications" AS "n"
// WHERE("n"."AllowedFrom" >= '08:00:00') AND("n"."AllowedTo" <= '16:00:00')
class Person
{
public int Id { get; set; }
public string Name { get; set; }
public DateOnly Birthday { get; set; }
}
class Notification
{
public int Id { get; set; }
public TimeOnly AllowedFrom { get; set; }
public TimeOnly AllowedTo { get; set; }
}
class ExampleContext : DbContext
{
public DbSet<Person> People { get; set; }
public DbSet<Notification> Notifications { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlite(@"Data Source=Db\DateOnlyTimeOnly.db");
}
2 SQLite connections are pooled
The SQLite database is a file. Therefore, in most cases, creating a connection is quick. However, opening a connection to an encrypted database can be very slow. As a result, in EF Core 6, SQLite connections are now pooled, just like other database providers.
class Person
{
public int Id { get; set; }
public string Name { get; set; }
}
class ExampleContext : DbContext
{
public DbSet<Person> People { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlite("Data Source=EncryptedDb.db;Mode=ReadWriteCreate;Password=password");
}
3 Commands in SQLite timed out
在 EF Core 6 的 SQLite 中，支持添加 Command Timeout 命令到连接字符串中，你可以用它来指定 SQLite 的默认超时时间。
class Person
{
public int Id { get; set; }
public string Name { get; set; }
}
class ExampleContext : DbContext
{
public DbSet<Person> People { get; set; }
// 60 seconds as the default timeout for commands created by connection
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlite("Data Source=Test.db;Command Timeout=60");
}
4 Savepoints in SQLite
In EF Core 6.0, SQLite supports Savepoints. You can save, roll back, and release savepoints.
var dbPath = Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, "..\\..\\..\\Savepoints.db"));
using var connection = new SqliteConnection($"Data Source={dbPath}");
connection.Open();
using var transaction = connection.BeginTransaction();
// The insert is committed to the database
using (var command = connection.CreateCommand())
{
command.CommandText = @"INSERT INTO People (Name) VALUES ('Oleg')";
command.ExecuteNonQuery();
}
transaction.Save("MySavepoint");
// The update is not commited since savepoint is rolled back before commiting the transaction
using (var command = connection.CreateCommand())
{
command.CommandText = @"UPDATE People SET Name = 'Not Oleg' WHERE Id = 1";
command.ExecuteNonQuery();
}
transaction.Rollback("MySavepoint");
transaction.Commit();
5 Required properties for in-memory database verification
In EF Core 6.0, In-memory databases verify required (In-momory) attributes. If you try to save an entity whose required attribute values are null, an exception occurs. You can disable this verification if necessary.
using var context = new ExampleContext();
var blog = new Blog();
context.Blogs.Add(blog);
await context.SaveChangesAsync();
// Unhandled exception. Microsoft.EntityFrameworkCore.DbUpdateException:
// Required properties '{'Title'}' are missing for the instance of entity
// type 'Blog' with the key value '{Id: 1}'.
class Blog
{
public int Id { get; set; }
[Required]
public string Title { get; set; }
}
class ExampleContext : DbContext
{
public DbSet<Blog> Blogs { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options
.EnableSensitiveDataLogging()
.LogTo(Console.WriteLine, new[] { InMemoryEventId.ChangesSaved })
.UseInMemoryDatabase("ValidateRequiredProps");
// To disable the validation
// .UseInMemoryDatabase("ValidateRequiredProps", b => b.EnableNullChecks(false));
}
6 EF. Functions. Contains method
在 EF Core 6.0 中，你可以使用 EF.Functions.Contains 方法来处理使用值转换器映射的列（也可以处理二进制列）。
using var context = new ExampleContext();
var query = context.People
.Where(e => EF.Functions.Contains(e.FullName, "Oleg"))
.ToQueryString();
Console.WriteLine(query);
// SELECT[p].[Id], [p].[FullName]
// FROM[People] AS[p]
// WHERE CONTAINS([p].[FullName], N'Oleg')
class Person
{
public int Id { get; set; }
public FullName FullName { get; set; }
}
public class FullName
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
class ExampleContext : DbContext
{
public DbSet<Person> People { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Person>()
.Property(x => x.FullName)
.HasConversion(
v => JsonSerializer.Serialize(v, (JsonSerializerOptions)null),
v => JsonSerializer.Deserialize<FullName>(v, (JsonSerializerOptions)null));
}
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6Contains");
}
7 Ending
本文所有代码示例都可以在我的 GitHub 中找到：https://github.com/okyrylchuk/dotnet6_features/tree/main/EF%20Core%206#miscellaneous-enhancements
Original: https://www.example.com
Author: Oleg Kyrylchuk
Translation: Exquisite Code Farmer