Use TryAdd in AddXxx methods to only add services if not already present.

src/EntityFramework.AzureTableStorage/Extensions/EntityServicesBuilderExtensions.cs

@@ -20,7 +20,7 @@ public static EntityServicesBuilder AddAzureTableStorage([NotNull] this EntitySe
         {
             Check.NotNull(builder, "builder");
 
-            builder.ServiceCollection
+            builder.ServiceCollection.TryAdd(new ServiceCollection()
                 .AddSingleton<AtsQueryFactory>()
                 .AddSingleton<TableEntityAdapterFactory>()
                 .AddSingleton<AtsValueReaderFactory>()
@@ -31,7 +31,7 @@ public static EntityServicesBuilder AddAzureTableStorage([NotNull] this EntitySe
                 .AddScoped<AtsDatabase>()
                 .AddScoped<AtsDataStore>()
                 .AddScoped<AtsConnection>()
-                .AddScoped<AtsDataStoreCreator>();
+                .AddScoped<AtsDataStoreCreator>());
 
             return builder;
         }

src/EntityFramework.InMemory/Extensions/InMemoryEntityServicesBuilderExtensions.cs

@@ -18,7 +18,7 @@ public static EntityServicesBuilder AddInMemoryStore([NotNull] this EntityServic
         {
             Check.NotNull(builder, "builder");
 
-            builder.ServiceCollection
+            builder.ServiceCollection.TryAdd(new ServiceCollection()
                 .AddSingleton<InMemoryValueGeneratorCache>()
                 .AddSingleton<InMemoryValueGeneratorSelector>()
                 .AddSingleton<SimpleValueGeneratorFactory<InMemoryValueGenerator>>()
@@ -28,7 +28,7 @@ public static EntityServicesBuilder AddInMemoryStore([NotNull] this EntityServic
                 .AddScoped<InMemoryDatabaseFacade>()
                 .AddScoped<InMemoryDataStore>()
                 .AddScoped<InMemoryConnection>()
-                .AddScoped<InMemoryDataStoreCreator>();
+                .AddScoped<InMemoryDataStoreCreator>());
 
             return builder;
         }

src/EntityFramework.Migrations/MigrationsEntityServicesBuilderExtensions.cs

@@ -17,9 +17,10 @@ public static EntityServicesBuilder AddMigrations([NotNull] this EntityServicesB
 
             builder
                 .AddRelational().ServiceCollection
-                .AddScoped<MigrationAssembly>()
-                .AddScoped<HistoryRepository>()
-                .AddScoped(MigrationsDataStoreServices.MigratorFactory);
+                .TryAdd(new ServiceCollection()
+                    .AddScoped<MigrationAssembly>()
+                    .AddScoped<HistoryRepository>()
+                    .AddScoped(MigrationsDataStoreServices.MigratorFactory));
 
             return builder;
         }

src/EntityFramework.Redis/Extensions/RedisEntityServicesBuilderExtensions.cs

@@ -15,7 +15,7 @@ public static EntityServicesBuilder AddRedis([NotNull] this EntityServicesBuilde
         {
             Check.NotNull(builder, "builder");
 
-            builder.ServiceCollection
+            builder.ServiceCollection.TryAdd(new ServiceCollection()
                 .AddSingleton<RedisValueGeneratorSelector>()
                 .AddSingleton<RedisValueGeneratorCache>()
                 .AddSingleton<RedisValueGeneratorFactory>()
@@ -25,7 +25,7 @@ public static EntityServicesBuilder AddRedis([NotNull] this EntityServicesBuilde
                 .AddScoped<RedisDataStoreServices>()
                 .AddScoped<RedisConnection>()
                 .AddScoped<RedisDataStoreCreator>()
-                .AddScoped<RedisDatabase>();
+                .AddScoped<RedisDatabase>());
 
             return builder;
         }

src/EntityFramework.Redis/RedisDataStore.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
@@ -21,6 +22,15 @@ public class RedisDataStore : DataStore
     {
         private readonly DbContextService<RedisDatabase> _database;
 
+        /// <summary>
+        ///     This constructor is intended only for use when creating test doubles that will override members
+        ///     with mocked or faked behavior. Use of this constructor for other purposes may result in unexpected
+        ///     behavior including but not limited to throwing <see cref="NullReferenceException" />.
+        /// </summary>
+        protected RedisDataStore()
+        {
+        }
+
         public RedisDataStore(
              [NotNull] StateManager stateManager,
              [NotNull] DbContextService<IModel> model,

src/EntityFramework.Relational/RelationalEntityServicesBuilderExtensions.cs

@@ -18,12 +18,12 @@ public static EntityServicesBuilder AddRelational([NotNull] this EntityServicesB
         {
             Check.NotNull(builder, "builder");
 
-            builder.ServiceCollection
+            builder.ServiceCollection.TryAdd(new ServiceCollection()
                 .AddSingleton<RelationalObjectArrayValueReaderFactory>()
                 .AddSingleton<RelationalTypedValueReaderFactory>()
                 .AddSingleton<ParameterNameGeneratorFactory>()
                 .AddSingleton<ModificationCommandComparer>()
-                .AddSingleton<GraphFactory, BidirectionalAdjacencyListGraphFactory>();
+                .AddSingleton<GraphFactory, BidirectionalAdjacencyListGraphFactory>());
 
             return builder;
         }

src/EntityFramework.SQLite/Extensions/SQLiteEntityServicesBuilderExtensions.cs

@@ -7,9 +7,9 @@
 using Microsoft.Data.Entity.Migrations.Infrastructure;
 using Microsoft.Data.Entity.Relational;
 using Microsoft.Data.Entity.Sqlite;
-using Microsoft.Data.Entity.Sqlite.Utilities;
 using Microsoft.Data.Entity.Sqlite.Metadata;
 using Microsoft.Data.Entity.Sqlite.Migrations;
+using Microsoft.Data.Entity.Sqlite.Utilities;
 using Microsoft.Data.Entity.Storage;
 
 // ReSharper disable once CheckNamespace
@@ -24,30 +24,31 @@ public static EntityServicesBuilder AddSqlite([NotNull] this EntityServicesBuild
 
             builder
                 .AddMigrations().ServiceCollection
-                .AddSingleton<SqliteValueGeneratorCache>()
-                .AddSingleton<SqliteValueGeneratorSelector>()
-                .AddSingleton<SqliteSqlGenerator>()
-                .AddSingleton<SqlStatementExecutor>()
-                .AddSingleton<SqliteTypeMapper>()
-                .AddSingleton<SqliteModificationCommandBatchFactory>()
-                .AddSingleton<SqliteCommandBatchPreparer>()
-                .AddSingleton<SqliteMetadataExtensionProvider>()
-                .AddSingleton<SqliteMigrationOperationFactory>()
-                .AddScoped<SqliteBatchExecutor>()
-                .AddScoped<DataStoreSource, SqliteDataStoreSource>()
-                .AddScoped<SqliteDataStoreServices>()
-                .AddScoped<SqliteDataStore>()
-                .AddScoped<SqliteConnection>()
-                .AddScoped<SqliteMigrationOperationSqlGeneratorFactory>()
-                .AddScoped<SqliteDataStoreCreator>()
-                .AddScoped<SqliteMigrator>()
-                .AddScoped<SqliteDatabase>()
-                // TODO: Move to an AddMigrations extension method?
-                // Issue #556                
-                .AddScoped<SqliteMigrationOperationProcessor>()
-                .AddScoped<SqliteModelDiffer>()
-                .AddScoped<MigrationAssembly>()
-                .AddScoped<HistoryRepository>();
+                .TryAdd(new ServiceCollection()
+                    .AddSingleton<SqliteValueGeneratorCache>()
+                    .AddSingleton<SqliteValueGeneratorSelector>()
+                    .AddSingleton<SqliteSqlGenerator>()
+                    .AddSingleton<SqlStatementExecutor>()
+                    .AddSingleton<SqliteTypeMapper>()
+                    .AddSingleton<SqliteModificationCommandBatchFactory>()
+                    .AddSingleton<SqliteCommandBatchPreparer>()
+                    .AddSingleton<SqliteMetadataExtensionProvider>()
+                    .AddSingleton<SqliteMigrationOperationFactory>()
+                    .AddScoped<SqliteBatchExecutor>()
+                    .AddScoped<DataStoreSource, SqliteDataStoreSource>()
+                    .AddScoped<SqliteDataStoreServices>()
+                    .AddScoped<SqliteDataStore>()
+                    .AddScoped<SqliteConnection>()
+                    .AddScoped<SqliteMigrationOperationSqlGeneratorFactory>()
+                    .AddScoped<SqliteDataStoreCreator>()
+                    .AddScoped<SqliteMigrator>()
+                    .AddScoped<SqliteDatabase>()
+                    // TODO: Move to an AddMigrations extension method?
+                    // Issue #556
+                    .AddScoped<SqliteMigrationOperationProcessor>()
+                    .AddScoped<SqliteModelDiffer>()
+                    .AddScoped<MigrationAssembly>()
+                    .AddScoped<HistoryRepository>());
 
             return builder;
         }

src/EntityFramework.SQLite/SQLiteDataStore.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using JetBrains.Annotations;
 using Microsoft.Data.Entity.ChangeTracking;
 using Microsoft.Data.Entity.Infrastructure;
@@ -11,13 +12,21 @@
 using Microsoft.Data.Entity.Relational.Query.Methods;
 using Microsoft.Data.Entity.Sqlite.Query;
 using Microsoft.Data.Entity.Sqlite.Utilities;
-using Microsoft.Data.Entity.Utilities;
 using Microsoft.Framework.Logging;
 
 namespace Microsoft.Data.Entity.Sqlite
 {
     public class SqliteDataStore : RelationalDataStore
     {
+        /// <summary>
+        ///     This constructor is intended only for use when creating test doubles that will override members
+        ///     with mocked or faked behavior. Use of this constructor for other purposes may result in unexpected
+        ///     behavior including but not limited to throwing <see cref="NullReferenceException" />.
+        /// </summary>
+        protected SqliteDataStore()
+        {
+        }
+
         public SqliteDataStore(
             [NotNull] StateManager stateManager,
             [NotNull] DbContextService<IModel> model,

src/EntityFramework.SqlServer/Extensions/SqlServerEntityServicesBuilderExtensions.cs

@@ -4,7 +4,7 @@
 using JetBrains.Annotations;
 using Microsoft.Data.Entity;
 using Microsoft.Data.Entity.Identity;
-using Microsoft.Data.Entity.Migrations.Infrastructure;
+using Microsoft.Data.Entity.Migrations;
 using Microsoft.Data.Entity.Relational;
 using Microsoft.Data.Entity.SqlServer;
 using Microsoft.Data.Entity.SqlServer.Metadata;
@@ -22,31 +22,30 @@ public static EntityServicesBuilder AddSqlServer([NotNull] this EntityServicesBu
         {
             Check.NotNull(builder, "builder");
 
-            builder.AddRelational().ServiceCollection
-                .AddSingleton<SqlServerValueGeneratorCache>()
-                .AddSingleton<SqlServerValueGeneratorSelector>()
-                .AddSingleton<SimpleValueGeneratorFactory<SequentialGuidValueGenerator>>()
-                .AddSingleton<SqlServerSequenceValueGeneratorFactory>()
-                .AddSingleton<SqlServerSqlGenerator>()
-                .AddSingleton<SqlStatementExecutor>()
-                .AddSingleton<SqlServerTypeMapper>()
-                .AddSingleton<SqlServerModificationCommandBatchFactory>()
-                .AddSingleton<SqlServerCommandBatchPreparer>()
-                .AddSingleton<SqlServerMetadataExtensionProvider>()
-                .AddSingleton<SqlServerMigrationOperationFactory>()
-                .AddScoped<SqlServerBatchExecutor>()
-                .AddScoped<DataStoreSource, SqlServerDataStoreSource>()
-                .AddScoped<SqlServerDataStoreServices>()
-                .AddScoped<SqlServerDataStore>()
-                .AddScoped<SqlServerConnection>()                
-                .AddScoped<SqlServerMigrationOperationProcessor>()
-                .AddScoped<SqlServerModelDiffer>()
-                .AddScoped<SqlServerDatabase>()
-                .AddScoped<SqlServerMigrationOperationSqlGeneratorFactory>()
-                .AddScoped<SqlServerDataStoreCreator>()
-                .AddScoped<MigrationAssembly>()
-                .AddScoped<HistoryRepository>()
-                .AddScoped<SqlServerMigrator>();
+            builder.AddMigrations().ServiceCollection
+                .TryAdd(new ServiceCollection()
+                    .AddSingleton<SqlServerValueGeneratorCache>()
+                    .AddSingleton<SqlServerValueGeneratorSelector>()
+                    .AddSingleton<SimpleValueGeneratorFactory<SequentialGuidValueGenerator>>()
+                    .AddSingleton<SqlServerSequenceValueGeneratorFactory>()
+                    .AddSingleton<SqlServerSqlGenerator>()
+                    .AddSingleton<SqlStatementExecutor>()
+                    .AddSingleton<SqlServerTypeMapper>()
+                    .AddSingleton<SqlServerModificationCommandBatchFactory>()
+                    .AddSingleton<SqlServerCommandBatchPreparer>()
+                    .AddSingleton<SqlServerMetadataExtensionProvider>()
+                    .AddSingleton<SqlServerMigrationOperationFactory>()
+                    .AddScoped<SqlServerBatchExecutor>()
+                    .AddScoped<DataStoreSource, SqlServerDataStoreSource>()
+                    .AddScoped<SqlServerDataStoreServices>()
+                    .AddScoped<SqlServerDataStore>()
+                    .AddScoped<SqlServerConnection>()
+                    .AddScoped<SqlServerMigrationOperationProcessor>()
+                    .AddScoped<SqlServerModelDiffer>()
+                    .AddScoped<SqlServerDatabase>()
+                    .AddScoped<SqlServerMigrationOperationSqlGeneratorFactory>()
+                    .AddScoped<SqlServerDataStoreCreator>()
+                    .AddScoped<SqlServerMigrator>());
 
             return builder;
         }

src/EntityFramework.SqlServer/SqlServerDataStore.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using JetBrains.Annotations;
 using Microsoft.Data.Entity.ChangeTracking;
 using Microsoft.Data.Entity.Infrastructure;
@@ -18,6 +19,15 @@ namespace Microsoft.Data.Entity.SqlServer
 {
     public class SqlServerDataStore : RelationalDataStore
     {
+        /// <summary>
+        ///     This constructor is intended only for use when creating test doubles that will override members
+        ///     with mocked or faked behavior. Use of this constructor for other purposes may result in unexpected
+        ///     behavior including but not limited to throwing <see cref="NullReferenceException" />.
+        /// </summary>
+        protected SqlServerDataStore()
+        {
+        }
+
         public SqlServerDataStore(
             [NotNull] StateManager stateManager,
             [NotNull] DbContextService<IModel> model,

src/EntityFramework/Extensions/EntityServiceCollectionExtensions.cs

@@ -2,8 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
 using JetBrains.Annotations;
 using Microsoft.Data.Entity;
 using Microsoft.Data.Entity.ChangeTracking;
@@ -31,7 +29,7 @@ public static EntityServicesBuilder AddEntityFramework(
         {
             Check.NotNull(serviceCollection, "serviceCollection");
 
-            serviceCollection
+            serviceCollection.TryAdd(new ServiceCollection()
                 .AddSingleton<IModelSource, DefaultModelSource>()
                 .AddSingleton<ModelBuilderFactory>()
                 .AddSingleton<SimpleValueGeneratorFactory<TemporaryValueGenerator>>()
@@ -77,45 +75,14 @@ public static EntityServicesBuilder AddEntityFramework(
                 .AddScoped(DataStoreServices.ConnectionFactory)
                 .AddScoped(DataStoreServices.DatabaseFactory)
                 .AddScoped(DataStoreServices.ValueGeneratorCacheFactory)
-                .AddScoped(DataStoreServices.DataStoreCreatorFactory);
-
-            EnsureLowLevelServices(serviceCollection);
+                .AddScoped(DataStoreServices.DataStoreCreatorFactory)
+                .AddSingleton<ILoggerFactory, LoggerFactory>()
+                .AddTypeActivator()
+                .AddOptions());
 
             return new EntityServicesBuilder(serviceCollection, configuration);
         }
 
-        private static void EnsureLowLevelServices(IServiceCollection serviceCollection)
-        {
-            var requiredServices = new List<Tuple<Type, Action<IServiceCollection>>>
-                {
-                    Tuple.Create<Type, Action<IServiceCollection>>(typeof(ILoggerFactory), c => c.AddSingleton<ILoggerFactory, LoggerFactory>()),
-                    Tuple.Create<Type, Action<IServiceCollection>>(typeof(ITypeActivator), c => c.AddTypeActivator()),
-                    Tuple.Create<Type, Action<IServiceCollection>>(typeof(IOptions<>), c => c.AddOptions()),
-                };
-
-            foreach (var descriptor in serviceCollection)
-            {
-                foreach (var serviceTuple in requiredServices)
-                {
-                    if (serviceTuple.Item1 == descriptor.ServiceType)
-                    {
-                        requiredServices.Remove(serviceTuple);
-                        break;
-                    }
-                }
-
-                if (!requiredServices.Any())
-                {
-                    break;
-                }
-            }
-
-            foreach (var serviceTuple in requiredServices)
-            {
-                serviceTuple.Item2(serviceCollection);
-            }
-        }
-
         public static EntityServicesBuilder AddDbContext<TContext>(
             [NotNull] this EntityServicesBuilder builder,
             [CanBeNull] Action<DbContextOptions> optionsAction = null)

test/EntityFramework.InMemory.Tests/InMemoryEntityServicesBuilderExtensionsTest.cs

@@ -6,6 +6,7 @@
 using Microsoft.Data.Entity.Storage;
 using Microsoft.Data.Entity.Tests;
 using Microsoft.Framework.DependencyInjection;
+using Microsoft.Framework.DependencyInjection.Fallback;
 using Xunit;
 
 namespace Microsoft.Data.Entity.InMemory.Tests
@@ -33,5 +34,22 @@ public void Services_wire_up_correctly()
                 Assert.NotNull(scopedProvider.GetRequiredService<DataStoreSource>());
             }
         }
+
+        [Fact]
+        public void AddInMemoryStore_does_not_replace_services_already_registered()
+        {
+            var services = new ServiceCollection()
+                .AddSingleton<InMemoryDataStore, FakeInMemoryDataStore>();
+
+            services.AddEntityFramework().AddInMemoryStore();
+
+            var serviceProvider = services.BuildServiceProvider();
+
+            Assert.IsType<FakeInMemoryDataStore>(serviceProvider.GetRequiredService<InMemoryDataStore>());
+        }
+
+        private class FakeInMemoryDataStore : InMemoryDataStore
+        {
+        }
     }
 }