Order collection navigations loaded by a Select projection

readme.md

@@ -16,6 +16,7 @@ https://nuget.org/packages/EfOrderBy/
 
 - **Automatic ordering**: Queries without explicit `OrderBy` automatically use configured default ordering
 - **Include() support**: Nested collections in `.Include()` expressions are automatically ordered
+- **Projection support**: Collection navigations loaded by a `.Select()` projection are automatically ordered
 - **Deterministic paging**: Ordering is applied before `Skip`/`Take`/`First`, so pages and single results are stable
 - **Inheritance support**: Ordering configured on a base entity type is automatically inherited by derived types (TPH)
 - **Fluent configuration**: Configure default ordering using the familiar EF Core fluent API
@@ -132,6 +133,34 @@ var departments = await context.Departments
 <!-- endSnippet -->
 
 
+## Projection Support
+
+A collection navigation read inside a `Select` projection is loaded by a subquery of its own, and is ordered the same way as one in an `Include`:
+
+<!-- snippet: ProjectionSupport -->
+<a id='snippet-ProjectionSupport'></a>
+```cs
+// Departments ordered by DisplayOrder
+// Employees ordered by HireDate, then Salary descending
+var departments = await context.Departments
+    .Select(_ => new
+    {
+        _.Name,
+        Employees = _.Employees
+            .Where(employee => employee.Salary > 0)
+            .Select(employee => employee.Name)
+            .ToList()
+    })
+    .ToListAsync();
+```
+<sup><a href='/src/Tests/Snippets.cs#L155-L170' title='Snippet source file'>snippet source</a> | <a href='#snippet-ProjectionSupport' title='Start of snippet'>anchor</a></sup>
+<!-- endSnippet -->
+
+The ordering goes after any `Where` filters and before the operators that project the entity away or choose which rows come back: `Select`, `Skip`, `Take`, `First`, `FirstOrDefault`, `Last`, `LastOrDefault`, `ElementAt`, `ElementAtOrDefault`, `ToList`, `ToArray` and `AsEnumerable`. A navigation bound into the result as it is, such as `new { _.Name, _.Employees }`, is ordered too.
+
+A collection whose order cannot reach the result is left alone: one that is only aggregated, with `Count`, `Any`, `Sum` and the like, or one composed with an operator EF Core drops ordering beneath, such as `Distinct`. Explicit ordering inside the projection is kept, and is checked by [redundant ordering detection](#detect-redundant-ordering) the same way as ordering inside an `Include`.
+
+
 ## Inheritance Support
 
 When using TPH (Table Per Hierarchy) inheritance, ordering configured on a base entity type is automatically inherited by derived types. This eliminates the need to duplicate `.OrderBy()` on every derived type.
@@ -182,7 +211,7 @@ public class InheritanceDbContext : DbContext
     public DbSet<DerivedEntityB> DerivedEntitiesB => Set<DerivedEntityB>();
 }
 ```
-<sup><a href='/src/Tests/Snippets.cs#L228-L273' title='Snippet source file'>snippet source</a> | <a href='#snippet-InheritanceOrdering' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Tests/Snippets.cs#L250-L295' title='Snippet source file'>snippet source</a> | <a href='#snippet-InheritanceOrdering' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 Behavior:
@@ -205,7 +234,7 @@ builder.Entity<Product>()
     .ThenBy(_ => _.Name)
     .ThenByDescending(_ => _.Price);
 ```
-<sup><a href='/src/Tests/Snippets.cs#L153-L160' title='Snippet source file'>snippet source</a> | <a href='#snippet-MultiColumnOrdering' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Tests/Snippets.cs#L175-L182' title='Snippet source file'>snippet source</a> | <a href='#snippet-MultiColumnOrdering' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 
@@ -548,7 +577,7 @@ public class AppDbContext : DbContext
     public DbSet<Employee> Employees => Set<Employee>();
 }
 ```
-<sup><a href='/src/Tests/Snippets.cs#L164-L207' title='Snippet source file'>snippet source</a> | <a href='#snippet-CompleteExample' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Tests/Snippets.cs#L186-L229' title='Snippet source file'>snippet source</a> | <a href='#snippet-CompleteExample' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 

src/Directory.Build.props

@@ -5,7 +5,7 @@
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
-    <Version>1.3.0</Version>
+    <Version>1.4.0</Version>
     <AssemblyVersion>1.0.0</AssemblyVersion>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>

src/EfOrderBy/GlobalUsings.cs

@@ -1,4 +1,5 @@
 global using System.Collections.Concurrent;
+global using System.Diagnostics.CodeAnalysis;
 global using System.Linq.Expressions;
 global using EfOrderBy;
 global using Microsoft.EntityFrameworkCore;

src/EfOrderBy/Interceptor.cs

@@ -24,18 +24,24 @@ public Expression QueryCompilationStarting(Expression query, QueryExpressionEven
         var detectRedundantOrdering = extension?.ThrowOnRedundantOrderBy ??
                                       OrderBySettings.ThrowOnRedundantOrderBy;
 
-        // Analyze the query for ordering and includes in a single pass
-        var (hasOrdering, hasInclude) = QueryAnalyzer.Analyze(query);
+        // Analyze the query for ordering, includes and projections in a single pass
+        var (hasOrdering, hasInclude, hasSelect) = QueryAnalyzer.Analyze(query);
 
         var queryWithOrderedIncludes = query;
 
         // Ordering nested collections rewrites the whole tree, so only do it when there is an
-        // Include to rewrite. Neither flag above can change as a result, since the rewrite only
-        // touches the inside of Include lambdas.
+        // Include or a projection to rewrite. None of the flags above can change as a result, since
+        // the rewrites only touch the inside of Include and Select lambdas.
         if (hasInclude)
         {
             var visitor = new IncludeOrderingApplicator(model, detectRedundantOrdering);
-            queryWithOrderedIncludes = visitor.Visit(query);
+            queryWithOrderedIncludes = visitor.Visit(queryWithOrderedIncludes);
+        }
+
+        if (hasSelect)
+        {
+            var visitor = new ProjectionOrderingApplicator(model, detectRedundantOrdering);
+            queryWithOrderedIncludes = visitor.Visit(queryWithOrderedIncludes);
         }
 
         if (hasOrdering)