NH-3807 - Guard System.Transactions, that is distributed transactions.

Author: ngbrown

src/NHibernate/AdoNet/ConnectionManager.cs

@@ -75,7 +75,11 @@ public bool IsInActiveTransaction
 			{
 				if (transaction != null && transaction.IsActive)
 					return true;
+#if FEATURE_SYSTEM_TRANSACTIONS
 				return Factory.TransactionFactory.IsInDistributedActiveTransaction(session);
+#else
+				return false;
+#endif
 			}
 		}
 

src/NHibernate/Cfg/SettingsFactory.cs

@@ -394,7 +394,13 @@ private static System.Type CreateLinqQueryProviderType(IDictionary<string, strin
 		private static ITransactionFactory CreateTransactionFactory(IDictionary<string, string> properties)
 		{
 			string className = PropertiesHelper.GetString(
-				Environment.TransactionStrategy, properties, typeof(AdoNetWithDistributedTransactionFactory).FullName);
+				Environment.TransactionStrategy, properties
+#if FEATURE_SYSTEM_TRANSACTIONS
+				, typeof(AdoNetWithDistributedTransactionFactory).FullName
+#else
+				, typeof(AdoNetTransactionFactory).FullName // No distributed transactions for .NET Core
+#endif
+				);
 			log.Info("Transaction factory: " + className);
 
 			try

src/NHibernate/Transaction/AdoNetWithDistributedTransactionFactory.cs

@@ -1,3 +1,5 @@
+#if FEATURE_SYSTEM_TRANSACTIONS
+
 using System;
 using System.Collections;
 using System.Transactions;
@@ -181,4 +183,6 @@ public void Dispose()
 			}
 		}
 	}
-}
+}
+
+#endif