Merge | SqlCommand Scalar Methods (#3619)

* Create partial file for Scalar execution

* Merge ExecuteScalar

* Merge CompleteExecuteScalar

* Merge ExecuteScalarAsync

* Merge InternalExecuteScalarAsync => ExecuteScalarAsyncInternal

* Merge ExecuteScalarBatchAsync

* Migrate ExecuteScalarUntilEndAsync

* Addressing @edwardneal's comments:
* Restore comment re: async untyped value getter
* Flip order of correlation event and trace event
* Introduce netfx style of result, success, return

* Adding <content> tags to the partials

Author: benrr101

src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj

@@ -582,6 +582,9 @@
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommand.cs">
       <Link>Microsoft\Data\SqlClient\SqlCommand.cs</Link>
     </Compile>
+    <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommand.Scalar.cs">
+      <Link>Microsoft\Data\SqlClient\SqlCommand.Scalar.cs</Link>
+    </Compile>
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommandSet.cs">
       <Link>Microsoft\Data\SqlClient\SqlCommandSet.cs</Link>
     </Compile>

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlCommand.netcore.cs

@@ -539,74 +539,6 @@ private SqlDataReader RunExecuteReaderWithRetry(
                 () => RunExecuteReader(cmdBehavior, runBehavior, returnStream, method));
         }
 
-        /// <include file='../../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlCommand.xml' path='docs/members[@name="SqlCommand"]/ExecuteScalar/*'/>
-        public override object ExecuteScalar()
-        {
-            // Reset _pendingCancel upon entry into any Execute - used to synchronize state
-            // between entry into Execute* API and the thread obtaining the stateObject.
-            _pendingCancel = false;
-
-            using (DiagnosticScope diagnosticScope = s_diagnosticListener.CreateCommandScope(this, _transaction))
-            using (TryEventScope.Create("SqlCommand.ExecuteScalar | API | ObjectId {0}", ObjectID))
-            {
-                SqlStatistics statistics = null;
-                bool success = false;
-                int? sqlExceptionNumber = null;
-                SqlClientEventSource.Log.TryCorrelationTraceEvent("SqlCommand.ExecuteScalar | API | Correlation | Object Id {0}, Activity Id {1}, Client Connection Id {2}, Command Text '{3}'", ObjectID, ActivityCorrelator.Current, Connection?.ClientConnectionId, CommandText);
-
-                try
-                {
-                    statistics = SqlStatistics.StartTimer(Statistics);
-                    WriteBeginExecuteEvent();
-                    SqlDataReader ds = IsProviderRetriable
-                        ? RunExecuteReaderWithRetry(0, RunBehavior.ReturnImmediately, returnStream: true)
-                        : RunExecuteReader(0, RunBehavior.ReturnImmediately, returnStream: true);
-                    success = true;
-                    return CompleteExecuteScalar(ds, _batchRPCMode);
-                }
-                catch (Exception ex)
-                {
-                    diagnosticScope.SetException(ex);
-                    if (ex is SqlException sqlException)
-                    {
-                        sqlExceptionNumber = sqlException.Number;
-                    }
-                    throw;
-                }
-                finally
-                {
-                    SqlStatistics.StopTimer(statistics);
-                    WriteEndExecuteEvent(success, sqlExceptionNumber, synchronous: true);
-                }
-            }
-        }
-
-        private object CompleteExecuteScalar(SqlDataReader ds, bool returnLastResult)
-        {
-            object retResult = null;
-
-            try
-            {
-                do
-                {
-                    if (ds.Read())
-                    {
-                        if (ds.FieldCount > 0)
-                        {
-                            retResult = ds.GetValue(0);
-                        }
-                    }
-                } while (returnLastResult && ds.NextResult());
-            }
-            finally
-            {
-                // clean off the wire
-                ds.Close();
-            }
-
-            return retResult;
-        }
-
         private Task InternalExecuteNonQueryWithRetry(
             bool sendToPipe,
             int timeout,
@@ -2291,186 +2223,6 @@ private void SetCachedCommandExecuteXmlReaderContext(ExecuteXmlReaderAsyncCallCo
             }
         }
 
-        /// <include file='../../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlCommand.xml' path='docs/members[@name="SqlCommand"]/ExecuteScalarAsync[@name="CancellationToken"]/*'/>
-        public override Task<object> ExecuteScalarAsync(CancellationToken cancellationToken) =>
-            // Do not use retry logic here as internal call to ExecuteReaderAsync handles retry logic.
-            InternalExecuteScalarAsync(cancellationToken);
-
-        private Task<object> InternalExecuteScalarAsync(CancellationToken cancellationToken)
-        {
-            SqlClientEventSource.Log.TryCorrelationTraceEvent("SqlCommand.InternalExecuteScalarAsync | API | Correlation | Object Id {0}, Activity Id {1}, Client Connection Id {2}, Command Text '{3}'", ObjectID, ActivityCorrelator.Current, Connection?.ClientConnectionId, CommandText);
-            SqlClientEventSource.Log.TryTraceEvent("SqlCommand.InternalExecuteScalarAsync | API> {0}, Client Connection Id {1}, Command Text = '{2}'", ObjectID, Connection?.ClientConnectionId, CommandText);
-            _parentOperationStarted = true;
-            Guid operationId = s_diagnosticListener.WriteCommandBefore(this, _transaction);
-
-            return ExecuteReaderAsync(cancellationToken).ContinueWith((executeTask) =>
-            {
-                TaskCompletionSource<object> source = new TaskCompletionSource<object>();
-                if (executeTask.IsCanceled)
-                {
-                    source.SetCanceled();
-                }
-                else if (executeTask.IsFaulted)
-                {
-                    s_diagnosticListener.WriteCommandError(operationId, this, _transaction, executeTask.Exception.InnerException);
-                    source.SetException(executeTask.Exception.InnerException);
-                }
-                else
-                {
-                    SqlDataReader reader = executeTask.Result;
-                    reader.ReadAsync(cancellationToken)
-                        .ContinueWith((Task<bool> readTask) =>
-                        {
-                            try
-                            {
-                                if (readTask.IsCanceled)
-                                {
-                                    reader.Dispose();
-                                    source.SetCanceled();
-                                }
-                                else if (readTask.IsFaulted)
-                                {
-                                    reader.Dispose();
-                                    s_diagnosticListener.WriteCommandError(operationId, this, _transaction, readTask.Exception.InnerException);
-                                    source.SetException(readTask.Exception.InnerException);
-                                }
-                                else
-                                {
-                                    Exception exception = null;
-                                    object result = null;
-                                    try
-                                    {
-                                        bool more = readTask.Result;
-                                        if (more && reader.FieldCount > 0)
-                                        {
-                                            try
-                                            {
-                                                result = reader.GetValue(0);
-                                            }
-                                            catch (Exception e)
-                                            {
-                                                exception = e;
-                                            }
-                                        }
-                                    }
-                                    finally
-                                    {
-                                        reader.Dispose();
-                                    }
-                                    if (exception != null)
-                                    {
-                                        s_diagnosticListener.WriteCommandError(operationId, this, _transaction, exception);
-                                        source.SetException(exception);
-                                    }
-                                    else
-                                    {
-                                        s_diagnosticListener.WriteCommandAfter(operationId, this, _transaction);
-                                        source.SetResult(result);
-                                    }
-                                }
-                            }
-                            catch (Exception e)
-                            {
-                                // exception thrown by Dispose...
-                                source.SetException(e);
-                            }
-                        },
-                        TaskScheduler.Default
-                    );
-                }
-                _parentOperationStarted = false;
-                return source.Task;
-            }, TaskScheduler.Default).Unwrap();
-        }
-
-        internal Task<object> ExecuteScalarBatchAsync(CancellationToken cancellationToken)
-        {
-            _parentOperationStarted = true;
-            Guid operationId = s_diagnosticListener.WriteCommandBefore(this, _transaction);
-
-            return ExecuteReaderAsync(cancellationToken).ContinueWith((executeTask) =>
-            {
-                TaskCompletionSource<object> source = new TaskCompletionSource<object>();
-                if (executeTask.IsCanceled)
-                {
-                    source.SetCanceled();
-                }
-                else if (executeTask.IsFaulted)
-                {
-                    s_diagnosticListener.WriteCommandError(operationId, this, _transaction, executeTask.Exception.InnerException);
-                    source.SetException(executeTask.Exception.InnerException);
-                }
-                else
-                {
-                    SqlDataReader reader = executeTask.Result;
-                    ExecuteScalarUntilEndAsync(reader, cancellationToken).ContinueWith(
-                        (readTask) =>
-                        {
-                            try
-                            {
-                                if (readTask.IsCanceled)
-                                {
-                                    reader.Dispose();
-                                    source.SetCanceled();
-                                }
-                                else if (readTask.IsFaulted)
-                                {
-                                    reader.Dispose();
-                                    s_diagnosticListener.WriteCommandError(operationId, this, _transaction, readTask.Exception.InnerException);
-                                    source.SetException(readTask.Exception.InnerException);
-                                }
-                                else
-                                {
-                                    Exception exception = null;
-                                    object result = null;
-                                    try
-                                    {
-                                        result = readTask.Result;
-                                    }
-                                    finally
-                                    {
-                                        reader.Dispose();
-                                    }
-                                    if (exception != null)
-                                    {
-                                        s_diagnosticListener.WriteCommandError(operationId, this, _transaction, exception);
-                                        source.SetException(exception);
-                                    }
-                                    else
-                                    {
-                                        s_diagnosticListener.WriteCommandAfter(operationId, this, _transaction);
-                                        source.SetResult(result);
-                                    }
-                                }
-                            }
-                            catch (Exception e)
-                            {
-                                // exception thrown by Dispose...
-                                source.SetException(e);
-                            }
-                        },
-                        TaskScheduler.Default
-                    );
-                }
-                _parentOperationStarted = false;
-                return source.Task;
-            }, TaskScheduler.Default).Unwrap();
-        }
-
-        private async Task<object> ExecuteScalarUntilEndAsync(SqlDataReader reader, CancellationToken cancellationToken)
-        {
-            object retval = null;
-            do
-            {
-                if (await reader.ReadAsync(cancellationToken).ConfigureAwait(false) && reader.FieldCount > 0)
-                {
-                    retval = reader.GetValue(0); // no async untyped value getter, this will work ok as long as the value is in the current packet
-                }
-            }
-            while (_batchRPCMode && !cancellationToken.IsCancellationRequested && await reader.NextResultAsync(cancellationToken).ConfigureAwait(false));
-            return retval;
-        }
-
         /// <include file='../../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlCommand.xml' path='docs/members[@name="SqlCommand"]/ExecuteXmlReaderAsync[@name="default"]/*'/>
         public Task<XmlReader> ExecuteXmlReaderAsync() => 
             ExecuteXmlReaderAsync(CancellationToken.None);

src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj

@@ -750,6 +750,9 @@
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommand.cs">
       <Link>Microsoft\Data\SqlClient\SqlCommand.cs</Link>
     </Compile>
+    <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommand.Scalar.cs">
+      <Link>Microsoft\Data\SqlClient\SqlCommand.Scalar.cs</Link>
+    </Compile>
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\SqlCommandBuilder.cs">
       <Link>Microsoft\Data\SqlClient\SqlCommandBuilder.cs</Link>
     </Compile>