Ignore reenlistment of same transaction. Fixes #619

Author: bgrainger

src/MySqlConnector/Core/ImplicitTransactionBase.cs

@@ -9,6 +9,8 @@ internal abstract class ImplicitTransactionBase : IEnlistmentNotification
 	{
 		public MySqlConnection Connection { get; }
 
+		public Transaction Transaction { get; private set; }
+
 		public void Start(Transaction transaction)
 		{
 			Transaction = transaction;
@@ -42,8 +44,6 @@ void IEnlistmentNotification.Rollback(Enlistment enlistment)
 
 		protected ImplicitTransactionBase(MySqlConnection connection) => Connection = connection;
 
-		protected Transaction Transaction { get; private set; }
-
 		protected abstract void OnStart();
 		protected abstract void OnPrepare(PreparingEnlistment enlistment);
 		protected abstract void OnCommit(Enlistment enlistment);

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

@@ -85,6 +85,10 @@ private async Task<MySqlTransaction> BeginDbTransactionAsync(IsolationLevel isol
 #if !NETSTANDARD1_3
 		public override void EnlistTransaction(System.Transactions.Transaction transaction)
 		{
+			// ignore reenlistment of same connection in same transaction
+			if (m_implicitTransaction?.Transaction.Equals(transaction) ?? false)
+				return;
+
 			if (m_implicitTransaction != null)
 				throw new MySqlException("Already enlisted in a Transaction.");
 			if (CurrentTransaction != null)

tests/SideBySide/TransactionScopeTests.cs

@@ -26,6 +26,19 @@ public TransactionScopeTests(DatabaseFixture database)
 #endif
 		};
 
+		[Theory]
+		[MemberData(nameof(ConnectionStrings))]
+		public void EnlistSameTransaction(string connectionString)
+		{
+			using (new TransactionScope())
+			using (var connection = new MySqlConnection(AppConfig.ConnectionString + ";" + connectionString))
+			{
+				connection.Open();
+				connection.EnlistTransaction(System.Transactions.Transaction.Current);
+				connection.EnlistTransaction(System.Transactions.Transaction.Current);
+			}
+		}
+
 		[Theory]
 		[MemberData(nameof(ConnectionStrings))]
 		public void EnlistTwoTransactions(string connectionString)