Merge pull request #21341 from abpframework/ef9linq

ABP Community Article: `EF Core 9 LINQ & SQL translation`

docs/en/Community-Articles/2024-11-14-EF-Core-9-Linq-SQL-Translation/POST.md

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+# EF Core 9 LINQ & SQL translation
+
+EF Core improves the translation of LINQ queries to SQL with every release. EF Core 9 is no exception. This article will show you some of the improvements in EF Core 9.
+
+EF Core 9 includes a lot of improvements in LINQ to SQL translation. we don't cover all of them in this article. You can find more information in the [official release notes](https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-9.0/whatsnew#linq-and-sql-translation).
+
+## Support for complex types
+
+### GroupBy
+
+EF Core now supports grouping by complex type instance. For example:
+
+```csharp
+var groupedAddress = await context.Customers
+    .GroupBy(c => new { c.Address })
+    .Select(g => new { g.Key, Count = g.Count() })
+    .ToListAsync();
+```
+
+Address is a complex type as a value object here.
+
+### ExecuteUpdate
+
+EF Core now supports updating a complex type. For example:
+
+```csharp
+var newAddress = new Address("New Street", "New City", "New Country");
+
+await context.Customers
+    .Where(e => e.Region == "Turkey")
+    .ExecuteUpdateAsync(s => s.SetProperty(b => b.Address, newAddress));
+```
+
+EF Core updates each column of the complex type.
+
+## Prune unneeded elements from SQL
+
+Ef Core now translates LINQ queries to SQL more efficiently. It will remove unneeded elements from the SQL query and bring better performance.
+
+### Table pruning
+
+When you use table-per-hierarchy (TPH) inheritance, previously EF Core generated SQL queries that included JIONs to tables that were not needed.
+
+For example:
+
+```csharp
+public class Order
+{
+    public int Id { get; set; }
+    ...
+
+    public Customer Customer { get; set; }
+}
+
+public class DiscountedOrder : Order
+{
+    public double Discount { get; set; }
+}
+
+public class Customer
+{
+    public int Id { get; set; }
+    ...
+
+    public List<Order> Orders { get; set; }
+}
+
+public class AppContext : DbContext
+{
+    ...
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.Entity<Order>().UseTptMappingStrategy();
+    }
+}
+```
+
+Consider the following query to get all customers with at least one order:
+
+```csharp
+var customers = await context.Customers.Where(o => o.Orders.Any()).ToListAsync();
+```
+
+Previously, EF Core generated the following SQL query:
+
+```sql
+SELECT [c].[Id], [c].[Name]
+FROM [Customers] AS [c]
+WHERE EXISTS (
+    SELECT 1
+    FROM [Orders] AS [o]
+    LEFT JOIN [DiscountedOrders] AS [d] ON [o].[Id] = [d].[Id]
+    WHERE [c].[Id] = [o].[CustomerId])
+```
+
+It included a JOIN to the `DiscountedOrders` table, which was not needed. In EF Core 9, the generated SQL query is:
+
+```sql
+SELECT [c].[Id], [c].[Name]
+FROM [Customers] AS [c]
+WHERE EXISTS (
+    SELECT 1
+    FROM [Orders] AS [o]
+    WHERE [c].[Id] = [o].[CustomerId])
+```
+
+## EF Core in ABP
+
+ABP Framework is built on top of the latest technologies. It will support EF Core 9 as soon as it is released. You can use the latest features of EF Core in your ABP applications.
+
+For example, you can use the `ExecuteUpdateAsync` method in your ABP application:
+
+```csharp
+public class Book : FullAuditedAggregateRoot<Guid>
+{
+    public string Name { get; set; }
+
+    public float Price { get; set; }
+
+    public string Author { get; set; }
+}
+
+public class AppContext : AbpDbContext<AppContext>
+{
+    public DbSet<Book> Books { get; set; }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        base.OnModelCreating(builder);
+
+        builder.Entity<Book>(b =>
+        {
+            b.ToTable("Books");
+            b.ConfigureByConvention();
+            b.Property(x => x.Name).IsRequired().HasMaxLength(128);
+            b.Property(x => x.Author).IsRequired().HasMaxLength(64);
+        });
+    }
+}
+
+public class BookRepository : EfCoreRepository<AppContext, Book, Guid>, IBookRepository
+{
+    public BookRepository(IDbContextProvider<AppContext> dbContextProvider)
+        : base(dbContextProvider)
+    {
+    }
+    
+    public async Task UpdatePriceByAuthorAsync(string author, float price)
+    {
+        await (await GetDbSetAsync())
+            .Where(b => b.Author == author)
+            .ExecuteUpdateAsync(b => b.SetProperty(x => x.Price, price));
+    }
+}
+```
+
+* `FullAuditedAggregateRoot` is an aggregate root base class with auditing properties provided by ABP Framework.
+* `IRepository` is a generic repository interface provided by ABP Framework that provides CRUD operations and you can use EF Core's API in your entity repository implementation.
+
+## References
+
+* [LINQ and SQL translation](https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-9.0/whatsnew#linq-and-sql-translation)
+* [ABP Entity Framework Core Integration](https://abp.io/docs/latest/framework/data/entity-framework-core)
+* [ABP Entities](https://abp.io/docs/latest/framework/architecture/domain-driven-design/entities)