IGNITE-28106 .NET: Fix tx rollback to ignore connection errors

modules/platforms/dotnet/Apache.Ignite.Tests/Transactions/TransactionsTests.cs

@@ -415,6 +415,19 @@ await Client.Transactions.RunInTransactionAsync<int>(async tx =>
             Assert.IsFalse(hasVal);
         }
 
+        [Test]
+        public async Task TestRollBackOnClosedConnectionDoesNotThrow()
+        {
+            using var client = await IgniteClient.StartAsync(GetConfig());
+            await using var tx = await client.Transactions.BeginAsync();
+            await TestUtils.ForceLazyTxStart(tx, client);
+
+            // ReSharper disable once DisposeOnUsingVariable
+            client.Dispose();
+
+            Assert.DoesNotThrowAsync(() => tx.RollbackAsync());
+        }
+
         private class CustomTx : ITransaction
         {
             public bool IsReadOnly => false;

modules/platforms/dotnet/Apache.Ignite/Internal/Transactions/LazyTransaction.cs

@@ -108,7 +108,12 @@ public async Task CommitAsync()
     /// <inheritdoc/>
     public async Task RollbackAsync()
     {
-        if (TrySetState(StateRolledBack))
+        if (!TrySetState(StateRolledBack))
+        {
+            return;
+        }
+
+        try
         {
             var tx = await DoOpAsync(_tx, ClientOp.TxRollback).ConfigureAwait(false);
 
@@ -117,6 +122,10 @@ public async Task RollbackAsync()
                 _logger.LogTxRollbackTrace(tx.Id);
             }
         }
+        catch (IgniteClientConnectionException)
+        {
+            // Connection exception: tx rolled back on server. Ignore.
+        }
     }
 
     /// <inheritdoc/>