Oleg Kyrylchuk
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LINQ Enhancements in Entity Framework Core 6

LINQ Enhancements in Entity Framework Core 6

Oleg Kyrylchuk's photo
Oleg Kyrylchuk
·Jan 9, 2022·

10 min read

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Table of contents

In this post, I focus on LINQ query enhancements in Entity Framework Core 6.

Better Support for GroupBy Queries

EF Core 6.0 has better support for GroupBy queries.

  • Translates GroupBy followed by FirstOrDefault over a group
  • Expands navigations after the GroupBy
  • Supports selecting the top N results from a group
using var context = new ExampleContext();
var query = context.People
    .GroupBy(p => p.FirstName)
    .Select(g => g.OrderBy(e => e.FirstName)
                  .ThenBy(e => e.LastName)
                  .FirstOrDefault())
    .ToQueryString();
Console.WriteLine(query);

class Person
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public int LastName { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Person> People { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6GroupBy");
}

Translated SQL:

SELECT[t0].[Id], [t0].[FirstName], [t0].[LastName]
FROM (
SELECT[p].[FirstName]
   FROM [People] AS [p]
   GROUP BY [p].[FirstName]
) AS[t]
LEFT JOIN(
   SELECT[t1].[Id], [t1].[FirstName], [t1].[LastName]
   FROM (
       SELECT[p0].[Id], [p0].[FirstName], [p0].[LastName],
       ROW_NUMBER() OVER(PARTITION BY [p0].[FirstName]
       ORDER BY [p0].[FirstName], [p0].[LastName]) AS[row]
       FROM[People] AS[p0]
   ) AS[t1]
   WHERE[t1].[row] <= 1
) AS[t0] ON[t].[FirstName] = [t0].[FirstName]

String.Concat Translation with 3 and 4 Arguments

Previously EF Core translated string.Concat only with two arguments. EF Core 6.0 translates string.Concat with 3 and 4 arguments.

using var context = new ExampleContext();
string fullName = "SamuelLanghorneClemens";
var query = context.Blogs
    .Where(b => string.Concat(b.FirstName, b.MiddleName, b.LastName) == fullName)
    .ToQueryString();
Console.WriteLine(query);

class Blog
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string LastName { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6StringConcat");
}

Translated SQL:

DECLARE @__fullName_0 nvarchar(4000) = N'SamuelLanghorneClemens';

SELECT[b].[Id], [b].[FirstName], [b].[LastName], [b].[MiddleName]
FROM[Blogs] AS[b]
WHERE(COALESCE([b].[FirstName], N'') + (COALESCE([b].[MiddleName], N'') +COALESCE([b].[LastName], N ''))) = @__fullName_0

EF.Functions.FreeText Supports Binary Columns

Previously, you couldn't use EF.Functions.FreeText method on binary columns despite the SQL FreeText function supporting them. EF Core 6.0 fixes that.

using var context = new ExampleContext();
var query = context.Posts
    .Where(p => EF.Functions.FreeText(EF.Property<string>(p, "Content"), "Searching text"))
    .ToQueryString();
Console.WriteLine(query);

class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public byte[] Content { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Post> Posts { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Post>()
            .Property(x => x.Content)
            .HasColumnType("varbinary(max)");
    }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6FlexibleTextSearch");
}

Translated SQL:

SELECT[p].[Id], [p].[Content], [p].[Title]
FROM[Posts] AS[p]
WHERE FREETEXT([p].[Content], N'Searching text')

Translate ToString on SQLite

Starting with EF Core 5.0, ToString translation for SQL Server has been added. EF Core 6.0 also translates ToString for SQLite database provider. It can be helpful for text searches on non-string columns.

using var context = new ExampleContext();
var query = context.People
    .Where(u => EF.Functions.Like(u.PhoneNumber.ToString(), "%368%"))
    .ToQueryString();
Console.WriteLine(query);

class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public long PhoneNumber { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Person> People { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlite("Data Source=:memory:");
}

Translated SQL:

SELECT "p"."Id", "p"."Name", "p"."PhoneNumber"
FROM "People" AS "p"
WHERE CAST("p"."PhoneNumber" AS TEXT) LIKE '%368%'

EF.Functions.Random

EF Core 6.0 introduces a new EF.Functions.Random method. It maps SQL function RAND(). Translations have been implemented for SQL Server, SQLite, and Cosmos.

using var context = new ExampleContext();
var query = context.Posts
    .Where(p => p.Rating == (int)(EF.Functions.Random() * 5.0) + 1)
    .ToQueryString();
Console.WriteLine(query);

class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public int Rating { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Post> Posts { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6Random");
}

Translated SQL:

SELECT[p].[Id], [p].[Rating], [p].[Title]
FROM[Posts] AS[p]
WHERE[p].[Rating] = (CAST((RAND() * 5.0E0) AS int) + 1)

Improved SQL Server Translation for IsNullOrWhitespace

Previously, EF Core translated string.IsNullOrWhiteSpace into a trimming of value before checking if it's empty. EF Core 6.0 doesn't do trimming anymore.

using var context = new ExampleContext();
var query = context.Entities
                    .Where(e => string.IsNullOrWhiteSpace(e.Property))
                    .ToQueryString();
Console.WriteLine(query);

class Entity
{
    public int Id { get; set; }
    public string Property { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Entity> Entities { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6IsNullOrWhiteSpace");
}

Previously translated SQL:

SELECT [e].[Id], [e].[Property]
FROM [Entities] AS[e]
WHERE [e].[Property] IS NULL OR (LTRIM(RTRIM([e].[Property])) = N'')

Translated SQL now:

SELECT [e].[Id], [e].[Property]
FROM [Entities] AS[e]
WHERE [e].[Property] IS NULL OR ([e].[Property] = N'')

Defining Query for In-memory Provider

In EF Core 6.0, you can define a query against the in-memory database for a given type with a new method ToInMemoryQuery. This is most useful for creating the equivalent of views on the memory databases.

using var context = new ExampleContext();
var blogEn = new Blog
{
    Title = "All about .NET",
    Language = "English",
    Posts = new List<Post>
        {
            new Post { Title = "Post one", Content = "Some content" },
            new Post { Title = "Post two", Content = "Some content" }
        }
};
var blogPl = new Blog
{
    Title = "Wszystko o .NET",
    Language = "Polish",
    Posts = new List<Post>
        {
            new Post { Title = "Pierwszy post", Content = "Treść" }
        }
};
context.Blogs.Add(blogEn);
context.Blogs.Add(blogPl);
await context.SaveChangesAsync();

var postsByLanguages = context.PostsByLanguages.ToList();
postsByLanguages
    .ForEach(p => Console.WriteLine($"{p.PostCount} posts in {p.Language}"));
// Output:
// 2 posts in English
// 1 posts in Polish

class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }
}
class Blog
{
    public int Id { get; set; }
    public string Title { get; set; }
    public string Language { get; set; }
    public ICollection<Post> Posts { get; set; }
}
class PostsByLanguage
{
    public string Language { get; set; }
    public int PostCount { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Post> Posts { get; set; }
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<PostsByLanguage> PostsByLanguages { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder
                .Entity<PostsByLanguage>()
                .HasNoKey()
                .ToInMemoryQuery(
                    () => Blogs
                        .GroupBy(c => c.Language)
                        .Select(
                            g =>
                                new PostsByLanguage
                                {
                                    Language = g.Key,
                                    PostCount = g.Sum(b => b.Posts.Count)
                                }));
    }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseInMemoryDatabase("ToInMemoryQuery");
}

Substring Translation with a Single Parameter

Previously EF Core translated only string.Substring overload with two parameters. EF Core 6.0 translates string.Substring with a single parameter.

using var context = new ExampleContext();
context.People.Add(new Person { Name = "John" });
context.People.Add(new Person { Name = "Bred" });
context.People.Add(new Person { Name = "Ron" });
await context.SaveChangesAsync();

var result = await context.People
    .Select(a => new { Name = a.Name.Substring(1) })
    .ToListAsync();
result.ForEach(p => Console.WriteLine(p.Name));
// Output:
// ohn
// red
// on

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.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6Substring");
}

Translated SQL:

SELECT SUBSTRING([p].[Name], 1 + 1, LEN([p].[Name])) AS [Name]
FROM [People] AS [p]

Split-queries for Non-navigation Collections

EF Core supports splitting a single LINQ query into multiple SQL queries. EF Core 6.0 can split a LINQ query where non-navigation collections are contained in the query projection.

using var context = new ExampleContext();
var blog = new Blog { Name = ".NET Blog"};
blog.Posts.Add(new Post { Title = "First .NET post" });
blog.Posts.Add(new Post { Title = "Second Java post" });
blog.Posts.Add(new Post { Title = "Third .NET post" });
context.Blogs.Add(blog);
await context.SaveChangesAsync();

var blogsWithDotnetPosts = await context.Blogs
    .Select(b => new
    {
        b,
        Posts = b.Posts.Where(p => p.Title.Contains(".NET")),
    })
    .AsSplitQuery()
    .ToListAsync();

class Blog
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Post> Posts { get; set; } = new List<Post>();
}
class Post
{
    public int Id { get; set; }
    public string Title { get; set; }
    public Blog Blog { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options
        .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6SplitQueries");
}

Single SQL query:

SELECT [b].[Id], [b].[Name], [t].[BlogId], [t].[Title]
FROM [Blogs] AS [b]
LEFT JOIN (
     SELECT [p].[Id], [p].[BlogId], [p].[Title]
     FROM [Posts] AS [p]
     WHERE [p].[Title] LIKE N'%.NET%'
) AS [t] ON [b].[Id] = [t].[BlogId]
ORDER BY [b].[Id]

Multiple SQL queries:

SELECT [b].[Id], [b].[Name]
FROM [Blogs] AS [b]
ORDER BY [b].[Id]

SELECT [t].[Id], [t].[BlogId], [t].[Title], [b].[Id]
FROM [Blogs] AS [b]
INNER JOIN (
     SELECT [p].[Id], [p].[BlogId], [p].[Title]
     FROM [Posts] AS [p]
     WHERE [p].[Title] LIKE N'%.NET%'
) AS [t] ON [b].[Id] = [t].[BlogId]
ORDER BY [b].[Id]

Remove Last ORDER BY Clause

When joining related entities, EF Core adds ORDER BY clauses to ensure all related entities for a given entity are grouped together. However, the last clause is not necessary and can have an impact on performance. EF Core 6.0 removes it.

using var context = new ExampleContext();
var query = context.Blogs
    .Include(b => b.Posts.Where(p => p.Rating > 3))
    .ToQueryString();
Console.WriteLine(query);

class Blog
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Post> Posts { get; set; }
}
class Post 
{
    public int Id { get; set; }
    public string Title { get; set; }
    public int Rating { get; set; }
    public Blog Blog { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6RemoveLastOrderByClause");
}

Translated SQL by EF Core 5.0:

SELECT [b].[Id], [b].[Name], [t].[Id], [t].[BlogId], [t].[Rating], [t].[Title]
FROM [Blogs] AS [b]
LEFT JOIN (
    SELECT [p].[Id], [p].[BlogId], [p].[Rating], [p].[Title]
    FROM [Posts] AS [p]
    WHERE [p].[Rating] > 3
) AS [t] ON [b].[Id] = [t].[BlogId]
ORDER BY [b].[Id], [t].[Id]

Translated SQL by EF Core 6.0:

SELECT [b].[Id], [b].[Name], [t].[Id], [t].[BlogId], [t].[Rating], [t].[Title]
FROM [Blogs] AS [b]
LEFT JOIN (
    SELECT [p].[Id], [p].[BlogId], [p].[Rating], [p].[Title]
    FROM [Posts] AS [p]
    WHERE [p].[Rating] > 3
) AS [t] ON [b].[Id] = [t].[BlogId]
ORDER BY [b].[Id]

Tag Queries with the File Name and Line Number

Starting with EF Core 2.2, you could add a tag to your query for better debug purposes. EF Core 6.0 went further, and now you can tag queries with the filename and line number of the LINQ code.

using var context = new ExampleContext();
var query = context.Blogs
    .TagWithCallSite()
    .OrderBy(b => b.CreationDate)
    .Take(10)
    .ToQueryString();
Console.WriteLine(query);

class Blog
{
    public int Id { get; set; }
    public string Name { get; set; }
    public DateTime CreationDate { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6TagWithCallSite");
}

Translated SQL:

DECLARE @__p_0 int = 10;

--File: D:\EFCore6\TagWithCallSite\TagWithCallSite\Program.cs:6

SELECT TOP(@__p_0) [b].[Id], [b].[CreationDate], [b].[Name]
FROM[Blogs] AS[b]
ORDER BY[b].[CreationDate]

Changes to Owned Optional Dependent Handling

EF Core 6.0 introduces some changes for owned optional dependent handling. When a model has owned optional dependent, EF Core will warn you when you save it with all missing properties.

using var context = new ExampleContext();
var person = new Person
{
    FirstName = "Oleg",
    LastName = "Kyrylchuk",
    Address = new Address()
};
context.People.Add(person);
await context.SaveChangesAsync();

class Person
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Address Address { get; set; }
}
class Address
{
    public string City { get; set; }
    public string Street { get; set; }
    public string PostalCode { get; set; }
}
class ExampleContext : DbContext
{
    public DbSet<Person> People { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder
            .Entity<Person>()
            .OwnsOne(p => p.Address);
    }
    protected override void OnConfiguring(DbContextOptionsBuilder options)
        => options
        .EnableSensitiveDataLogging()
        .LogTo(Console.WriteLine)
        .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6OwnedDependentHandling");
}

Warning in logs: warning log.png

When you have nested owned optional dependents, EF Core will not allow creating the model at all.

using var context = new ExampleContext();
var person = new Person
{
   FirstName = "Oleg",
   LastName = "Kyrylchuk",
   ContactInfo = new ContactInfo()
};
context.People.Add(person);
await context.SaveChangesAsync();

class Person
{
   public int Id { get; set; }
   public string FirstName { get; set; }
   public string LastName { get; set; }
   public ContactInfo ContactInfo { get; set; }
}
class ContactInfo
{
   public string Phone { get; set; }
   public Address Address { get; set; }
}
class Address
{
   public string City { get; set; }
   public string Street { get; set; }
   public string PostalCode { get; set; }
}
class ExampleContext : DbContext
{
   public DbSet<Person> People { get; set; }
   protected override void OnModelCreating(ModelBuilder modelBuilder)
   {
       modelBuilder
           .Entity<Person>()
           .OwnsOne(p => p.ContactInfo)
           .OwnsOne(p => p.Address);
   }
   protected override void OnConfiguring(DbContextOptionsBuilder options)
       => options.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFCore6OwnedDependentHandling");
}

An exception is thrown when the model is created: error log.png

The changes force you to avoid such cases. You can fix them by:

  • making dependent required,
  • making at least one required property in the dependent,
  • creating own tables for optional dependents, instead of sharing them with the principal.

Wrapping Up

All code samples you can find on my GitHub.

 
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