correct internal connection transaction promotion

Author: Wraith2

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

@@ -2047,7 +2047,7 @@ internal void OnEnvChange(SqlEnvChange rec)
                     break;
 
                 case TdsEnums.ENV_PROMOTETRANSACTION:
-                    byte[] dtcToken = null;
+                    byte[] dtcToken;
                     if (rec._newBinRented)
                     {
                         dtcToken = new byte[rec._newLength];

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -2506,7 +2506,18 @@ internal void OnEnvChange(SqlEnvChange rec)
                     break;
 
                 case TdsEnums.ENV_PROMOTETRANSACTION:
-                    PromotedDTCToken = rec._newBinValue;
+                    byte[] dtcToken;
+                    if (rec._newBinRented)
+                    {
+                        dtcToken = new byte[rec._newLength];
+                        Buffer.BlockCopy(rec._newBinValue, 0, dtcToken, 0, dtcToken.Length);
+                    }
+                    else
+                    {
+                        dtcToken = rec._newBinValue;
+                        rec._newBinValue = null;
+                    }
+                    PromotedDTCToken = dtcToken;
                     break;
 
                 case TdsEnums.ENV_TRANSACTIONENDED:

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlEnvChange.cs

@@ -48,7 +48,6 @@ internal void Clear()
                 {
                     ArrayPool<byte>.Shared.Return(_newBinValue);
                 }
-
                 _newBinValue = null;
             }
             if (_oldBinValue != null)

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/TransactionTest/TransactionEnlistmentTest.cs

@@ -51,6 +51,10 @@ public static void TestManualEnlistment_Enlist_TxScopeComplete()
         [ConditionalFact(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsNotAzureServer))]
         public static void TestEnlistmentPrepare_TxScopeComplete()
         {
+            if (!System.Diagnostics.Debugger.IsAttached)
+            {
+                System.Diagnostics.Debugger.Launch();
+            }
             try
             {
                 using TransactionScope txScope = new(TransactionScopeOption.RequiresNew, new TransactionOptions()