Updated following design meeting feedback

src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs

@@ -179,7 +179,7 @@ public void Dispose()
                 }
 
                 public void Reset()
-                    => throw new NotSupportedException();
+                    => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
             }
 
             private sealed class AsyncEnumerator : IAsyncEnumerator<T>

src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs

@@ -290,7 +290,7 @@ public ValueTask DisposeAsync()
                 }
 
                 public void Reset()
-                    => throw new NotSupportedException();
+                    => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
 
                 private bool ShapeResult()
                 {

src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Linq.Expressions;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Query;
 using Microsoft.EntityFrameworkCore.Utilities;
 using Newtonsoft.Json.Linq;
@@ -110,7 +111,7 @@ protected override Expression VisitShapedQuery(ShapedQueryExpression shapedQuery
                             QueryCompilationContext.QueryTrackingBehavior == QueryTrackingBehavior.NoTrackingWithIdentityResolution));
 
                 default:
-                    throw new NotSupportedException();
+                    throw new NotSupportedException(CoreStrings.UnhandledExpressionNode(shapedQueryExpression.QueryExpression));
             }
         }
     }

src/EFCore.Cosmos/Storage/Internal/CosmosClientWrapper.cs

@@ -763,7 +763,7 @@ public void Dispose()
                 }
 
                 public void Reset()
-                    => throw new NotSupportedException();
+                    => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
             }
         }
 

src/EFCore.InMemory/Query/Internal/InMemoryShapedQueryCompilingExpressionVisitor.QueryingEnumerable.cs

@@ -160,7 +160,7 @@ public ValueTask DisposeAsync()
                 }
 
                 public void Reset()
-                    => throw new NotSupportedException();
+                    => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
             }
         }
     }

src/EFCore.Relational/Migrations/Migration.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Migrations.Operations;
 
@@ -118,9 +119,7 @@ protected virtual void BuildTargetModel([NotNull] ModelBuilder modelBuilder)
         /// </summary>
         /// <param name="migrationBuilder"> The <see cref="MigrationBuilder" /> that will build the operations. </param>
         protected virtual void Down([NotNull] MigrationBuilder migrationBuilder)
-        {
-            throw new NotImplementedException();
-        }
+            => throw new NotSupportedException(RelationalStrings.MigrationDownMissing);
 
         private List<MigrationOperation> BuildOperations(Action<MigrationBuilder> buildAction)
         {

src/EFCore.Relational/Properties/RelationalStrings.resx

@@ -608,6 +608,9 @@
   <data name="MethodOnNonTPHRootNotSupported" xml:space="preserve">
     <value>Using '{methodName}' on DbSet of '{entityType}' is not supported since '{entityType}' is part of hierarchy and does not contain a discriminator property.</value>
   </data>
+  <data name="MigrationDownMissing" xml:space="preserve">
+    <value>The 'Down' method for this migration has not been implemented. Both the 'Up' abd 'Down' methods must be implemented to support reverting migrations.</value>
+  </data>
   <data name="MigrationNotFound" xml:space="preserve">
     <value>The migration '{migrationName}' was not found.</value>
   </data>

src/EFCore.Relational/Query/EntityProjectionExpression.cs

@@ -41,7 +41,7 @@ private readonly IDictionary<INavigation, EntityShaperExpression> _ownedNavigati
         [Obsolete("Use the constructor which takes populated column expressions map.", error: true)]
         public EntityProjectionExpression([NotNull] IEntityType entityType, [NotNull] TableExpressionBase innerTable, bool nullable)
         {
-            throw new NotSupportedException();
+            throw new NotSupportedException("Obsolete: Use the constructor which takes populated column expressions map.");
         }
 
         /// <summary>

src/EFCore.Relational/Query/Internal/FromSqlQueryingEnumerable.cs

@@ -235,7 +235,7 @@ public void Dispose()
             }
 
             public void Reset()
-                => throw new NotSupportedException();
+                => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
         }
 
         private sealed class AsyncEnumerator : IAsyncEnumerator<T>

src/EFCore.Relational/Query/Internal/SingleQueryingEnumerable.cs

@@ -229,7 +229,7 @@ public void Dispose()
             }
 
             public void Reset()
-                => throw new NotSupportedException();
+                => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
         }
 
         private sealed class AsyncEnumerator : IAsyncEnumerator<T>

src/EFCore.Relational/Query/Internal/SplitQueryingEnumerable.cs

@@ -235,7 +235,7 @@ public void Dispose()
             }
 
             public void Reset()
-                => throw new NotSupportedException();
+                => throw new NotSupportedException(CoreStrings.EnumerableResetNotSupported);
         }
 
         private sealed class AsyncEnumerator : IAsyncEnumerator<T>

src/EFCore.Relational/Storage/IRelationalCommand.cs

@@ -108,7 +108,6 @@ Task<RelationalDataReader> ExecuteReaderAsync(
         DbCommand CreateDbCommand(
             RelationalCommandParameterObject parameterObject,
             Guid commandId,
-            DbCommandMethod commandMethod)
-            => throw new NotSupportedException();
+            DbCommandMethod commandMethod);
     }
 }

src/EFCore.Relational/Storage/IRelationalConnection.cs

@@ -30,11 +30,7 @@ public interface IRelationalConnection : IRelationalTransactionManager, IDisposa
         /// <summary>
         ///     Gets or sets the connection string for the database.
         /// </summary>
-        string ConnectionString
-        {
-            get => throw new NotSupportedException();
-            [param: CanBeNull] set => throw new NotSupportedException();
-        }
+        string ConnectionString { get; [param: CanBeNull] set; }
 
         /// <summary>
         ///     <para>
@@ -47,11 +43,7 @@ string ConnectionString
         ///         Note that the connection must be disposed by application code since it was not created by Entity Framework.
         ///     </para>
         /// </summary>
-        DbConnection DbConnection
-        {
-            get => throw new NotSupportedException();
-            [param: CanBeNull] set => throw new NotSupportedException();
-        }
+        DbConnection DbConnection { get; [param: CanBeNull] set; }
 
         /// <summary>
         ///     The <see cref="DbContext" /> currently in use, or null if not known.

src/EFCore.SqlServer/Properties/SqlServerStrings.resx

@@ -262,6 +262,9 @@
   <data name="NonKeyValueGeneration" xml:space="preserve">
     <value>The property '{property}' on entity type '{entityType}' is configured to use 'SequenceHiLo' value generator, which is only intended for keys. If this was intentional, configure an alternate key on the property, otherwise call 'ValueGeneratedNever' or configure store generation for this property.</value>
   </data>
+  <data name="NoSavepointRelease" xml:space="preserve">
+    <value>SQL Server does not support releasing a savepoint.</value>
+  </data>
   <data name="SequenceBadType" xml:space="preserve">
     <value>SQL Server sequences cannot be used to generate values for the property '{property}' on entity type '{entityType}' because the property type is '{propertyType}'. Sequences can only be used with integer properties.</value>
   </data>

src/EFCore.SqlServer/Storage/Internal/SqlServerSqlGenerationHelper.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Text;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.SqlServer.Internal;
 using Microsoft.EntityFrameworkCore.Storage;
 using Microsoft.EntityFrameworkCore.Utilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -124,6 +125,6 @@ public override string GenerateRollbackToSavepointStatement(string name)
         /// <param name="name"> The name of the savepoint to be released. </param>
         /// <returns> An SQL string to release the savepoint. </returns>
         public override string GenerateReleaseSavepointStatement(string name)
-            => throw new NotSupportedException("SQL Server does not support releasing a savepoint");
+            => throw new NotSupportedException(SqlServerStrings.NoSavepointRelease);
     }
 }

src/EFCore/Properties/CoreStrings.resx

@@ -423,6 +423,9 @@
   <data name="EntityTypesNotInRelationship" xml:space="preserve">
     <value>The provided entity types '{invalidDependentType}' and '{invalidPrincipalType}' are invalid. Specify '{dependentType}' and '{principalType}', or entity types in the same hierarchy.</value>
   </data>
+  <data name="EnumerableResetNotSupported" xml:space="preserve">
+    <value>This enumerator cannot be reset.</value>
+  </data>
   <data name="ErrorInvalidQueryable" xml:space="preserve">
     <value>Cannot use multiple context instances within a single query execution. Ensure the query uses a single context instance.</value>
   </data>
@@ -1288,6 +1291,9 @@
   <data name="RuntimeParameterMissingParameter" xml:space="preserve">
     <value>While registering a runtime parameter, the lambda expression must have only one parameter which must be same as 'QueryCompilationContext.QueryContextParameter' expression.</value>
   </data>
+  <data name="SavepointsNotSupported" xml:space="preserve">
+    <value>Savepoints are not supported by the database provider in use.</value>
+  </data>
   <data name="SeedDatumDefaultValue" xml:space="preserve">
     <value>The seed entity for entity type '{entityType}' cannot be added because a default value was provided for the required property '{property}'. Please provide a value different from '{defaultValue}'.</value>
   </data>

src/EFCore/Storage/IDbContextTransaction.cs

@@ -5,6 +5,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 
 namespace Microsoft.EntityFrameworkCore.Storage
@@ -58,7 +59,7 @@ public interface IDbContextTransaction : IDisposable, IAsyncDisposable
         /// </summary>
         /// <param name="name"> The name of the savepoint to be created. </param>
         void CreateSavepoint([NotNull] string name)
-            => throw new NotSupportedException();
+            => throw new NotSupportedException(CoreStrings.SavepointsNotSupported);
 
         /// <summary>
         ///     Creates a savepoint in the transaction. This allows all commands that are executed after the savepoint
@@ -70,14 +71,14 @@ void CreateSavepoint([NotNull] string name)
         /// <returns> A <see cref="Task" /> representing the asynchronous operation. </returns>
         /// <exception cref="OperationCanceledException"> If the <see cref="CancellationToken"/> is canceled. </exception>
         Task CreateSavepointAsync([NotNull] string name, CancellationToken cancellationToken = default)
-            => throw new NotSupportedException();
+            => throw new NotSupportedException(CoreStrings.SavepointsNotSupported);
 
         /// <summary>
         ///     Rolls back all commands that were executed after the specified savepoint was established.
         /// </summary>
         /// <param name="name"> The name of the savepoint to roll back to. </param>
         void RollbackToSavepoint([NotNull] string name)
-            => throw new NotSupportedException();
+            => throw new NotSupportedException(CoreStrings.SavepointsNotSupported);
 
         /// <summary>
         ///     Rolls back all commands that were executed after the specified savepoint was established.
@@ -87,7 +88,7 @@ void RollbackToSavepoint([NotNull] string name)
         /// <returns> A <see cref="Task" /> representing the asynchronous operation. </returns>
         /// <exception cref="OperationCanceledException"> If the <see cref="CancellationToken"/> is canceled. </exception>
         Task RollbackToSavepointAsync([NotNull] string name, CancellationToken cancellationToken = default)
-            => throw new NotSupportedException();
+            => throw new NotSupportedException(CoreStrings.SavepointsNotSupported);
 
         /// <summary>
         ///     <para>

test/EFCore.Relational.Tests/RelationalEventIdTest.cs

@@ -172,11 +172,9 @@ public string FindMigrationId(string nameOrId)
 
         private class FakeRelationalConnection : IRelationalConnection
         {
-            public string ConnectionString
-                => throw new NotImplementedException();
+            public string ConnectionString { get; set; }
 
-            public DbConnection DbConnection
-                => new FakeDbConnection();
+            public DbConnection DbConnection { get; set; } = new FakeDbConnection();
 
             public DbContext Context
                 => null;

test/EFCore.SqlServer.FunctionalTests/TestUtilities/TestRelationalCommandBuilderFactory.cs

@@ -1,9 +1,12 @@
 // Copyright (c) .NET Foundation. 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.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Storage;
 
@@ -203,6 +206,9 @@ public async Task<RelationalDataReader> ExecuteReaderAsync(
                 return result;
             }
 
+            public DbCommand CreateDbCommand(RelationalCommandParameterObject parameterObject, Guid commandId, DbCommandMethod commandMethod)
+                => throw new NotImplementedException();
+
             private int? PreExecution(IRelationalConnection connection)
             {
                 int? errorNumber = null;

test/EFCore.SqlServer.Tests/SqlServerDatabaseCreatorTest.cs

@@ -3,9 +3,11 @@
 
 using System;
 using System.Collections.Generic;
+using System.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Data.SqlClient;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal;
 using Microsoft.EntityFrameworkCore.Storage;
@@ -265,38 +267,31 @@ public IReadOnlyDictionary<string, object> ParameterValues
                 => throw new NotImplementedException();
 
             public int ExecuteNonQuery(RelationalCommandParameterObject parameterObject)
-            {
-                return 0;
-            }
+                => 0;
 
             public Task<int> ExecuteNonQueryAsync(
                 RelationalCommandParameterObject parameterObject,
                 CancellationToken cancellationToken = default)
                 => Task.FromResult(0);
 
             public RelationalDataReader ExecuteReader(RelationalCommandParameterObject parameterObject)
-            {
-                throw new NotImplementedException();
-            }
+                => throw new NotImplementedException();
 
             public Task<RelationalDataReader> ExecuteReaderAsync(
                 RelationalCommandParameterObject parameterObject,
                 CancellationToken cancellationToken = default)
-            {
-                throw new NotImplementedException();
-            }
+                => throw new NotImplementedException();
+
+            public DbCommand CreateDbCommand(RelationalCommandParameterObject parameterObject, Guid commandId, DbCommandMethod commandMethod)
+                => throw new NotImplementedException();
 
             public object ExecuteScalar(RelationalCommandParameterObject parameterObject)
-            {
-                throw new NotImplementedException();
-            }
+                => throw new NotImplementedException();
 
             public Task<object> ExecuteScalarAsync(
                 RelationalCommandParameterObject parameterObject,
                 CancellationToken cancellationToken = default)
-            {
-                throw new NotImplementedException();
-            }
+                => throw new NotImplementedException();
         }
     }
 }