fix(csharp): silently drop unrecognized SetOption flags for compatibility (#348)

## Summary

- When clients like Power BI set options not yet implemented in this
driver (e.g. `adbc.databricks.query_tags` from an older Mashup version),
the driver was throwing `AdbcException.NotImplemented` causing
unexpected failures
- `DatabricksStatement.SetOption` (Thrift path): calls
`base.SetOption(key, value)` and catches
`AdbcStatusCode.NotImplemented`, silently dropping unknown options while
preserving correct handling of any base-class options (e.g.
`PollTimeMilliseconds`, `QueryTimeoutSeconds`)
- `StatementExecutionStatement.SetOption` (SEA path): same pattern —
calls `base.SetOption(key, value)` and catches `NotImplemented` to
silently drop unknown options
- Both paths emit an `Activity` event
(`statement.set_option.unrecognized`) with the dropped key for
observability

## Test plan

- [x] Added
`StatementSetOptionTests.SetOption_UnrecognizedKey_DoesNotThrow` (SEA
path, `StatementExecutionStatement`)
- [x] Added
`DatabricksStatementTests.SetOption_UnrecognizedKey_DoesNotThrow`
(Thrift path, `DatabricksStatement`)
- [x] All 633 unit tests pass
- [x] Build succeeds for all target frameworks (`netstandard2.0`,
`net472`, `net8.0`)

Closes PECO-2952

This pull request was AI-assisted by Isaac.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: eric-wang-1990

csharp/src/DatabricksStatement.cs

@@ -382,7 +382,17 @@ public override void SetOption(string key, string value)
                     }
                     break;
                 default:
-                    base.SetOption(key, value);
+                    try
+                    {
+                        base.SetOption(key, value);
+                    }
+                    catch (AdbcException ex) when (ex.Status == AdbcStatusCode.NotImplemented)
+                    {
+                        // Silently drop unrecognized options for compatibility with clients
+                        // that may set options not yet supported by this driver.
+                        Activity.Current?.AddEvent(new ActivityEvent("statement.set_option.unrecognized",
+                            tags: new ActivityTagsCollection { { "key", key } }));
+                    }
                     break;
             }
         }

csharp/src/StatementExecution/StatementExecutionStatement.cs

@@ -199,7 +199,17 @@ public override void SetOption(string key, string value)
                     break;
 
                 default:
-                    base.SetOption(key, value);
+                    try
+                    {
+                        base.SetOption(key, value);
+                    }
+                    catch (AdbcException ex) when (ex.Status == AdbcStatusCode.NotImplemented)
+                    {
+                        // Silently drop unrecognized options for compatibility with clients
+                        // that may set options not yet supported by this driver.
+                        Activity.Current?.AddEvent(new ActivityEvent("statement.set_option.unrecognized",
+                            tags: new ActivityTagsCollection { { "key", key } }));
+                    }
                     break;
             }
         }

csharp/test/Unit/DatabricksStatementUnitTests.cs

@@ -126,5 +126,15 @@ public void CreateStatement_ConfOverlayInitiallyNull()
             var confOverlay = GetConfOverlay(statement);
             Assert.Null(confOverlay);
         }
+
+        /// <summary>
+        /// Tests that unrecognized options are silently dropped instead of throwing (PECO-2952).
+        /// </summary>
+        [Fact]
+        public void SetOption_UnrecognizedKey_DoesNotThrow()
+        {
+            using var statement = CreateStatement();
+            statement.SetOption("adbc.databricks.unknown_future_option", "some_value");
+        }
     }
 }

csharp/test/Unit/FeatureFlagCacheTests.cs

@@ -418,7 +418,7 @@ public async Task FeatureFlagContext_ConcurrentFlagAccess_ThreadSafe()
         public async Task FeatureFlagContext_BackgroundRefreshError_SetsActivityStatusToError()
         {
             // Arrange
-            var backgroundActivities = new List<(string Name, ActivityStatusCode Status, List<ActivityEvent> Events)>();
+            var backgroundActivities = new System.Collections.Concurrent.ConcurrentBag<(string Name, ActivityStatusCode Status, List<ActivityEvent> Events)>();
 
             var listener = new ActivityListener
             {

csharp/test/Unit/StatementExecution/StatementSetOptionTests.cs

@@ -0,0 +1,82 @@
+/*
+* Copyright (c) 2025 ADBC Drivers Contributors
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Http;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using AdbcDrivers.Databricks.StatementExecution;
+using AdbcDrivers.HiveServer2;
+using AdbcDrivers.HiveServer2.Spark;
+using Microsoft.IO;
+using Moq;
+using Moq.Protected;
+using Xunit;
+
+namespace AdbcDrivers.Databricks.Tests.Unit.StatementExecution
+{
+    /// <summary>
+    /// Unit tests verifying that unrecognized options are silently dropped by
+    /// StatementExecutionStatement.SetOption instead of throwing exceptions (PECO-2952).
+    /// </summary>
+    public class StatementSetOptionTests
+    {
+        [Fact]
+        public void SetOption_UnrecognizedKey_DoesNotThrow()
+        {
+            var properties = new Dictionary<string, string>
+            {
+                { SparkParameters.HostName, "test.databricks.com" },
+                { DatabricksParameters.WarehouseId, "wh-1" },
+                { SparkParameters.AccessToken, "token" },
+            };
+
+            var handlerMock = new Mock<HttpMessageHandler>();
+            handlerMock.Protected()
+                .Setup<Task<HttpResponseMessage>>("SendAsync",
+                    ItExpr.IsAny<HttpRequestMessage>(),
+                    ItExpr.IsAny<CancellationToken>())
+                .ReturnsAsync(new HttpResponseMessage(HttpStatusCode.OK)
+                {
+                    Content = new StringContent(
+                        JsonSerializer.Serialize(new { session_id = "s1" }))
+                });
+
+            using var httpClient = new HttpClient(handlerMock.Object);
+            using var connection = new StatementExecutionConnection(properties, httpClient);
+            using var statement = new StatementExecutionStatement(
+                client: Mock.Of<IStatementExecutionClient>(),
+                sessionId: "session-1",
+                warehouseId: "wh-1",
+                catalog: null,
+                schema: null,
+                resultDisposition: "INLINE_OR_EXTERNAL_LINKS",
+                resultFormat: "ARROW_STREAM",
+                resultCompression: null,
+                waitTimeoutSeconds: 0,
+                pollingIntervalMs: 50,
+                properties: properties,
+                recyclableMemoryStreamManager: new RecyclableMemoryStreamManager(),
+                lz4BufferPool: System.Buffers.ArrayPool<byte>.Shared,
+                httpClient: httpClient,
+                connection: connection);
+
+            statement.SetOption("adbc.databricks.unknown_future_option", "some_value");
+        }
+    }
+}