Ability to have projectable methods that accept a DbContext

tests/EntityFrameworkCore.Projectables.FunctionalTests/ComplexModelTests.ProjectOverMethodTakingDbContext.verified.txt

@@ -0,0 +1,10 @@
+SELECT [t0].[Id], [t0].[RecordDate], [t0].[UserId]
+FROM [User] AS [u]
+LEFT JOIN (
+    SELECT [t].[Id], [t].[RecordDate], [t].[UserId]
+    FROM (
+        SELECT [o].[Id], [o].[RecordDate], [o].[UserId], ROW_NUMBER() OVER(PARTITION BY [o].[UserId] ORDER BY [o].[RecordDate] DESC) AS [row]
+        FROM [Order] AS [o]
+    ) AS [t]
+    WHERE [t].[row] <= 1
+) AS [t0] ON [u].[Id] = [t0].[UserId]

tests/EntityFrameworkCore.Projectables.FunctionalTests/ComplexModelTests.cs

@@ -38,12 +38,18 @@ namespace EntityFrameworkCore.Projectables.FunctionalTests
             public IEnumerable<EntityFrameworkCore.Projectables.FunctionalTests.ComplexModelTests.Order> Last2Orders =>
                 Orders.OrderByDescending(x => x.RecordDate).Take(2);
 
+            [Projectable]
+            public EntityFrameworkCore.Projectables.FunctionalTests.ComplexModelTests.Order GetLastOrderFromExternalDbContext(DbContext dbContext)
+                => dbContext.Set<EntityFrameworkCore.Projectables.FunctionalTests.ComplexModelTests.Order>().Where(x => x.UserId == Id).OrderByDescending(x => x.RecordDate).FirstOrDefault();
+
         }
 
         public class Order
         {
             public int Id { get; set; }
 
+            public int UserId { get; set; }
+
             public DateTime RecordDate { get; set; }
         } 
 
@@ -69,5 +75,16 @@ namespace EntityFrameworkCore.Projectables.FunctionalTests
 
             return Verifier.Verify(query.ToQueryString());
         }
+
+        [Fact]
+        public Task ProjectOverMethodTakingDbContext()
+        {
+            using var dbContext = new SampleDbContext<User>();
+
+            var query = dbContext.Set<User>()
+                .Select(x => x.GetLastOrderFromExternalDbContext(dbContext));
+
+            return Verifier.Verify(query.ToQueryString());
+        }
     }
 }

tests/EntityFrameworkCore.Projectables.FunctionalTests/ExtensionsMethods/EntityExtensions.cs

@@ -1,4 +1,7 @@
-namespace EntityFrameworkCore.Projectables.FunctionalTests.ExtensionMethods
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+
+namespace EntityFrameworkCore.Projectables.FunctionalTests.ExtensionMethods
 {
     public static class EntityExtensions
     {
@@ -7,5 +10,9 @@
 
         [Projectable]
         public static int Foo(this Entity entity) => entity.Id + 1;
+
+        [Projectable]
+        public static Entity? LeadingEntity(this Entity entity, DbContext dbContext)
+            => dbContext.Set<Entity>().Where(y => y.Id > entity.Id).FirstOrDefault();
     }
 }

tests/EntityFrameworkCore.Projectables.FunctionalTests/ExtensionsMethods/ExtensionMethodTests.ExtensionMethodAcceptingDbContext.verified.txt

@@ -0,0 +1,7 @@
+SELECT [t].[Id]
+FROM [Entity] AS [e]
+OUTER APPLY (
+    SELECT TOP(1) [e0].[Id]
+    FROM [Entity] AS [e0]
+    WHERE [e0].[Id] > [e].[Id]
+) AS [t]

tests/EntityFrameworkCore.Projectables.FunctionalTests/ExtensionsMethods/ExtensionMethodTests.cs

@@ -5,6 +5,7 @@ using System.Text;
 using System.Threading.Tasks;
 using EntityFrameworkCore.Projectables.FunctionalTests.Helpers;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Scaffolding.Metadata;
 using ScenarioTests;
 using VerifyXunit;
 using Xunit;
@@ -36,5 +37,19 @@ namespace EntityFrameworkCore.Projectables.FunctionalTests.ExtensionMethods
 
             return Verifier.Verify(query.ToQueryString());
         }
+
+        [Fact]
+        public Task ExtensionMethodAcceptingDbContext()
+        {
+            using var dbContext = new SampleDbContext<Entity>();
+
+            var sampleQuery = dbContext.Set<Entity>()
+                .Select(x => dbContext.Set<Entity>().Where(y => y.Id > x.Id).FirstOrDefault());
+
+            var query = dbContext.Set<Entity>()
+                .Select(x => x.LeadingEntity(dbContext));
+
+            return Verifier.Verify(query.ToQueryString());
+        }
     }
 }