Lazily allocate MySqlParameterCollection.

This improves the performance of creating MySqlCommand objects with no parameters.

Author: bgrainger

src/MySqlConnector/Core/CachedProcedure.cs

@@ -63,7 +63,7 @@ private CachedProcedure(string schema, string component, ReadOnlyCollection<Cach
 		internal MySqlParameterCollection AlignParamsWithDb(MySqlParameterCollection parameterCollection)
 		{
 			var alignedParams = new MySqlParameterCollection();
-			var returnParam = parameterCollection.FirstOrDefault(x => x.Direction == ParameterDirection.ReturnValue);
+			var returnParam = parameterCollection?.FirstOrDefault(x => x.Direction == ParameterDirection.ReturnValue);
 
 			foreach (var cachedParam in Parameters)
 			{
@@ -74,7 +74,7 @@ internal MySqlParameterCollection AlignParamsWithDb(MySqlParameterCollection par
 				}
 				else
 				{
-					var index = parameterCollection.NormalizedIndexOf(cachedParam.Name);
+					var index = parameterCollection?.NormalizedIndexOf(cachedParam.Name) ?? -1;
 					alignParam = index >= 0 ? parameterCollection[index] : throw new ArgumentException($"Parameter '{cachedParam.Name}' not found in the collection.");
 				}
 

src/MySqlConnector/Core/PreparedStatementCommandExecutor.cs

@@ -67,11 +67,11 @@ private PayloadData CreateQueryPayload(PreparedStatement preparedStatement, MySq
 				for (var i = 0; i < preparedStatement.Statement.ParameterNames.Count; i++)
 				{
 					var parameterName = preparedStatement.Statement.ParameterNames[i];
-					var parameterIndex = parameterName != null ? parameterCollection.NormalizedIndexOf(parameterName) : preparedStatement.Statement.ParameterIndexes[i];
+					var parameterIndex = parameterName != null ? (parameterCollection?.NormalizedIndexOf(parameterName) ?? -1) : preparedStatement.Statement.ParameterIndexes[i];
 					if (parameterIndex == -1 && parameterName != null)
 						throw new MySqlException("Parameter '{0}' must be defined.".FormatInvariant(parameterName));
-					else if (parameterIndex < 0 || parameterIndex >= parameterCollection.Count)
-						throw new MySqlException("Parameter index {0} is invalid when only {1} parameter{2} defined.".FormatInvariant(parameterIndex, parameterCollection.Count, parameterCollection.Count == 1 ? " is" : "s are"));
+					else if (parameterIndex < 0 || parameterIndex >= (parameterCollection?.Count ?? 0))
+						throw new MySqlException("Parameter index {0} is invalid when only {1} parameter{2} defined.".FormatInvariant(parameterIndex, parameterCollection?.Count ?? 0, parameterCollection?.Count == 1 ? " is" : "s are"));
 					parameters[i] = parameterCollection[parameterIndex];
 				}
 

src/MySqlConnector/Core/StatementPreparer.cs

@@ -45,16 +45,16 @@ public ArraySegment<byte> ParseAndBindParameters()
 
 		private int GetParameterIndex(string name)
 		{
-			var index = m_parameters.NormalizedIndexOf(name);
+			var index = m_parameters?.NormalizedIndexOf(name) ?? -1;
 			if (index == -1 && (m_options & StatementPreparerOptions.AllowUserVariables) == 0)
 				throw new MySqlException("Parameter '{0}' must be defined. To use this as a variable, set 'Allow User Variables=true' in the connection string.".FormatInvariant(name));
 			return index;
 		}
 
 		private MySqlParameter GetInputParameter(int index)
 		{
-			if (index >= m_parameters.Count)
-				throw new MySqlException("Parameter index {0} is invalid when only {1} parameter{2} defined.".FormatInvariant(index, m_parameters.Count, m_parameters.Count == 1 ? " is" : "s are"));
+			if (index >= (m_parameters?.Count ?? 0))
+				throw new MySqlException("Parameter index {0} is invalid when only {1} parameter{2} defined.".FormatInvariant(index, m_parameters?.Count ?? 0, m_parameters?.Count == 1 ? " is" : "s are"));
 			var parameter = m_parameters[index];
 			if (parameter.Direction != ParameterDirection.Input && (m_options & StatementPreparerOptions.AllowOutputParameters) == 0)
 				throw new MySqlException("Only ParameterDirection.Input is supported when CommandType is Text (parameter name: {0})".FormatInvariant(parameter.ParameterName));

src/MySqlConnector/MySql.Data.MySqlClient/MySqlCommand.cs

@@ -41,7 +41,6 @@ public MySqlCommand(string commandText, MySqlConnection connection, MySqlTransac
 			CommandText = commandText;
 			Connection = connection;
 			Transaction = transaction;
-			m_parameterCollection = new MySqlParameterCollection();
 			CommandType = CommandType.Text;
 		}
 
@@ -50,6 +49,8 @@ public MySqlCommand(string commandText, MySqlConnection connection, MySqlTransac
 			get
 			{
 				VerifyNotDisposed();
+				if (m_parameterCollection == null)
+					m_parameterCollection = new MySqlParameterCollection();
 				return m_parameterCollection;
 			}
 		}
@@ -116,7 +117,7 @@ private bool NeedsPrepare(out Exception exception)
 
 		private async Task DoPrepareAsync(IOBehavior ioBehavior, CancellationToken cancellationToken)
 		{
-			var statementPreparer = new StatementPreparer(CommandText, Parameters, CreateStatementPreparerOptions());
+			var statementPreparer = new StatementPreparer(CommandText, m_parameterCollection, CreateStatementPreparerOptions());
 			var parsedStatements = statementPreparer.SplitStatements();
 
 			if (parsedStatements.Statements.Count > 1)
@@ -231,7 +232,7 @@ protected override DbConnection DbConnection
 			set => Connection = (MySqlConnection) value;
 		}
 
-		protected override DbParameterCollection DbParameterCollection => m_parameterCollection;
+		protected override DbParameterCollection DbParameterCollection => Parameters;
 
 		protected override DbTransaction DbTransaction
 		{
@@ -326,6 +327,7 @@ protected override void Dispose(bool disposing)
 			{
 				base.Dispose(disposing);
 			}
+			m_isDisposed = true;
 		}
 
 		/// <summary>
@@ -403,14 +405,14 @@ internal StatementPreparerOptions CreateStatementPreparerOptions()
 
 		private void VerifyNotDisposed()
 		{
-			if (m_parameterCollection == null)
+			if (m_isDisposed)
 				throw new ObjectDisposedException(GetType().Name);
 		}
 
 		private bool IsValid(out Exception exception)
 		{
 			exception = null;
-			if (m_parameterCollection == null)
+			if (m_isDisposed)
 				exception = new ObjectDisposedException(GetType().Name);
 			else if (Connection == null)
 				exception = new InvalidOperationException("Connection property must be non-null.");
@@ -429,6 +431,7 @@ private bool IsValid(out Exception exception)
 
 		static int s_commandId = 1;
 
+		bool m_isDisposed;
 		MySqlConnection m_connection;
 		string m_commandText;
 		MySqlParameterCollection m_parameterCollection;