feat(csharp): make the driver AOT/trim-safe under net10.0

csharp/Directory.Packages.props

@@ -16,6 +16,7 @@
 <Project>
   <PropertyGroup>
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+    <CentralPackageTransitivePinningEnabled>true</CentralPackageTransitivePinningEnabled>
   </PropertyGroup>
   <ItemGroup>
     <!-- Compression -->
@@ -33,6 +34,7 @@
     <PackageVersion Include="BenchmarkDotNet" Version="0.14.0" />
     <!-- System -->
     <PackageVersion Include="System.Collections.Immutable" Version="8.0.0" />
+    <PackageVersion Include="System.Memory" Version="4.6.3" />
     <PackageVersion Include="System.Reflection.Metadata" Version="8.0.0" />
     <PackageVersion Include="System.Net.Http" Version="4.3.4" />
     <!-- Resilience -->
@@ -44,5 +46,7 @@
     <!-- Protobuf (for telemetry schema testing) -->
     <PackageVersion Include="Google.Protobuf" Version="3.25.1" />
     <PackageVersion Include="Grpc.Tools" Version="2.60.0" />
+    <!-- Telemetry -->
+    <PackageVersion Include="OpenTelemetry.Api" Version="1.15.3" />
   </ItemGroup>
 </Project>

csharp/src/AdbcDrivers.Databricks.csproj

@@ -1,9 +1,21 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks Condition="'$(IsWindows)'=='true'">netstandard2.0;net472;net8.0</TargetFrameworks>
-		<TargetFrameworks Condition="'$(TargetFrameworks)'==''">netstandard2.0;net8.0</TargetFrameworks>
+    <TargetFrameworks Condition="'$(IsWindows)'=='true'">netstandard2.0;net472;net8.0;net10.0</TargetFrameworks>
+		<TargetFrameworks Condition="'$(TargetFrameworks)'==''">netstandard2.0;net8.0;net10.0</TargetFrameworks>
     <PackageReadmeFile>readme.md</PackageReadmeFile>
   </PropertyGroup>
+
+  <!--
+    Verify the driver is AOT/trim-safe under net10.0 without yet producing a
+    native build. IsAotCompatible turns on the trim, single-file, and AOT
+    Roslyn analyzers (and marks the assembly IsTrimmable) so a normal build
+    surfaces IL2xxx/IL3xxx warnings; with TreatWarningsAsErrors they fail the
+    build. The actual NativeAOT publish will live in a separate project.
+  -->
+  <PropertyGroup Condition="'$(TargetFramework)'=='net10.0'">
+    <IsAotCompatible>true</IsAotCompatible>
+    <EnableNETAnalyzers>true</EnableNETAnalyzers>
+  </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="K4os.Compression.LZ4" />
     <PackageReference Include="K4os.Compression.LZ4.Streams" />

csharp/src/ComplexTypeSerializingStream.cs

@@ -16,16 +16,17 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Text;
 using System.Text.Encodings.Web;
 using System.Text.Json;
-using System.Text.Json.Nodes;
 using System.Threading;
 using System.Threading.Tasks;
+using AdbcDrivers.Databricks.StatementExecution;
 using Apache.Arrow;
 using Apache.Arrow.Adbc.Extensions;
 using Apache.Arrow.Ipc;
 using Apache.Arrow.Types;
-using AdbcDrivers.Databricks.StatementExecution;
 
 namespace AdbcDrivers.Databricks
 {
@@ -75,7 +76,7 @@ internal sealed class ComplexTypeSerializingStream : IArrowArrayStream
         // a double quote becomes \" (not ") and non-ASCII / < > & are emitted verbatim
         // rather than \uXXXX-escaped. The output is still valid JSON; "unsafe" only refers to
         // embedding directly in HTML, which is the consuming application's concern, not ours.
-        private static readonly JsonSerializerOptions JsonOptions = new JsonSerializerOptions
+        private static readonly JsonWriterOptions WriterOptions = new JsonWriterOptions
         {
             Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
         };
@@ -139,12 +140,27 @@ private RecordBatch ConvertComplexColumns(RecordBatch batch)
         private static StringArray SerializeToStringArray(IArrowArray array)
         {
             StringArray.Builder builder = new StringArray.Builder();
+
+            // Write each value with a manual Utf8JsonWriter rather than JsonSerializer.Serialize.
+            // The value graph (ToObject) is a closed set of Arrow scalar types, lists, and
+            // dictionaries, so we can emit it without reflection — keeping this trim- and
+            // NativeAOT-safe. A single stream/writer pair is reused across rows to avoid
+            // per-row allocations.
+            using MemoryStream stream = new MemoryStream();
+            using Utf8JsonWriter writer = new Utf8JsonWriter(stream, WriterOptions);
             for (int i = 0; i < array.Length; i++)
             {
                 if (array.IsNull(i))
+                {
                     builder.AppendNull();
-                else
-                    builder.Append(JsonSerializer.Serialize(ToObject(array, i), JsonOptions));
+                    continue;
+                }
+
+                stream.SetLength(0);
+                writer.Reset(stream);
+                SerializeStructuredValue(writer, array, i);
+                writer.Flush();
+                builder.Append(Encoding.UTF8.GetString(stream.GetBuffer(), 0, (int)stream.Length));
             }
             return builder.Build();
         }
@@ -175,53 +191,123 @@ private static HashSet<int> DetectComplexColumns(Schema schema)
 
         // --- JSON serialization helpers ---
 
-        private static object? ToObject(IArrowArray array, int index)
+        private static void SerializeStructuredValue(Utf8JsonWriter writer, IArrowArray array, int index)
         {
             if (array.IsNull(index))
-                return null;
+            {
+                writer.WriteNullValue();
+                return;
+            }
 
-            // Handle complex types with recursive traversal, and types needing specific
-            // string formatting. All other primitives delegate to ValueAt().
-            return array switch
+            switch (array.Data.DataType.TypeId)
             {
-                ListArray la => ToListOrMap(la, index),
-                StructArray sa => ToDict(sa, index),
+                case ArrowTypeId.List:
+                case ArrowTypeId.Map: SerializeListOrMap(writer, (ListArray)array, index); break;
+                case ArrowTypeId.Struct: SerializeDict(writer, (StructArray)array, index); break;
                 // DECIMAL: emit as a bare JSON number (not a quoted string) so the output matches
                 // the JDBC driver and is valid JSON. The decimal's string form is written raw so
                 // values beyond C# decimal's ~28-digit range (DECIMAL(38, …)) keep full precision.
-                Decimal128Array dec => RawNumber(dec.GetString(index)),
-                Decimal256Array dec => RawNumber(dec.GetString(index)),
-                Date32Array d32 => d32.GetDateTime(index)?.ToString("yyyy-MM-dd"),
+                case ArrowTypeId.Decimal32: writer.WriteRawValue(((Decimal32Array)array).GetString(index)); break;
+                case ArrowTypeId.Decimal64: writer.WriteRawValue(((Decimal64Array)array).GetString(index)); break;
+                case ArrowTypeId.Decimal128: writer.WriteRawValue(((Decimal128Array)array).GetString(index)); break;
+                case ArrowTypeId.Decimal256: writer.WriteRawValue(((Decimal256Array)array).GetString(index)); break;
+                case ArrowTypeId.Date32: writer.WriteStringValue(((Date32Array)array).GetDateTime(index)!.Value.ToString("yyyy-MM-dd")); break;
+                case ArrowTypeId.Date64: writer.WriteStringValue(((Date64Array)array).GetDateTime(index)!.Value.ToString("yyyy-MM-dd")); break;
                 // INTERVAL: native YearMonth/Duration arrays serialize to {} via System.Text.Json
                 // (no public properties). Render the same "Y-M" / "D HH:MM:SS.nnnnnnnnn" strings
                 // IntervalSerializingStream produces for top-level interval columns.
-                YearMonthIntervalArray ym => IntervalSerializingStream.FormatYearMonth(ym.GetValue(index)!.Value.Months),
-                DurationArray dur => IntervalSerializingStream.FormatDuration(dur.GetValue(index)!.Value, ((DurationType)dur.Data.DataType).Unit),
-                _ => array.ValueAt(index, StructResultType.Object)      // int, long, double, float, bool, string, timestamp, etc.
-            };
-        }
+                case ArrowTypeId.Interval:
+                    switch (((IntervalType)array.Data.DataType).Unit)
+                    {
+                        case IntervalUnit.DayTime:
+                            var dayTime = ((DayTimeIntervalArray)array).GetValue(index)!.Value;
+                            var timeSpan = TimeSpan.FromDays(dayTime.Days) + TimeSpan.FromMilliseconds(dayTime.Milliseconds);
+                            writer.WriteStringValue(timeSpan.ToString());
+                            break;
+                        case IntervalUnit.MonthDayNanosecond:
+                            var monthDayNano = ((MonthDayNanosecondIntervalArray)array).GetValue(index)!.Value;
+                            timeSpan = TimeSpan.FromDays(monthDayNano.Days) + TimeSpan.FromTicks(monthDayNano.Nanoseconds / 100);
+                            writer.WriteStringValue(IntervalSerializingStream.FormatYearMonth(monthDayNano.Months) + " " + timeSpan.ToString());
+                            break;
+                        case IntervalUnit.YearMonth:
+                            writer.WriteStringValue(IntervalSerializingStream.FormatYearMonth(
+                                ((YearMonthIntervalArray)array).GetValue(index)!.Value.Months));
+                            break;
+                        default: writer.WriteNullValue(); break;
+                    }
+                    break;
+                case ArrowTypeId.Duration:
+                    DurationArray dur = (DurationArray)array;
+                    writer.WriteStringValue(IntervalSerializingStream.FormatDuration(dur.GetValue(index)!.Value, ((DurationType)dur.Data.DataType).Unit));
+                    break;
 
-        /// <summary>
-        /// Wraps a numeric string as a raw JSON number node so <see cref="JsonSerializer"/> emits it
-        /// unquoted (e.g. <c>1</c>, not <c>"1"</c>) with full precision.
-        /// </summary>
-        private static JsonNode? RawNumber(string? numericText) =>
-            numericText == null ? null : JsonNode.Parse(numericText);
+                case ArrowTypeId.Boolean: writer.WriteBooleanValue(((BooleanArray)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Double: writer.WriteNumberValue(((DoubleArray)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Float: writer.WriteNumberValue(((FloatArray)array).GetValue(index)!.Value); break;
+#if NET5_0_OR_GREATER
+                case ArrowTypeId.HalfFloat:
+                    var halfValue = ((HalfFloatArray)array).GetValue(index)!.Value;
+                    writer.WriteNumberValue((double)halfValue); break;
+#endif
+                case ArrowTypeId.Int8: writer.WriteNumberValue(((Int8Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Int16: writer.WriteNumberValue(((Int16Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Int32: writer.WriteNumberValue(((Int32Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Int64: writer.WriteNumberValue(((Int64Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.String: writer.WriteStringValue(((StringArray)array).GetString(index)); break;
+                case ArrowTypeId.LargeString: writer.WriteStringValue(((LargeStringArray)array).GetString(index)); break;
+#if NET6_0_OR_GREATER
+                case ArrowTypeId.Time32: writer.WriteStringValue(((Time32Array)array).GetTime(index)!.Value.ToString("HH:mm:ss.ffffff")); break;
+                case ArrowTypeId.Time64: writer.WriteStringValue(((Time64Array)array).GetTime(index)!.Value.ToString("HH:mm:ss.ffffff")); break;
+#else
+                case ArrowTypeId.Time32:
+                    Time32Array time32Array = (Time32Array)array;
+                    int time32 = time32Array.GetValue(index)!.Value;
+                    switch (((Time32Type)time32Array.Data.DataType).Unit)
+                    {
+                        case TimeUnit.Second: writer.WriteStringValue(TimeSpan.FromSeconds(time32).ToString()); break;
+                        case TimeUnit.Millisecond: writer.WriteStringValue(TimeSpan.FromMilliseconds(time32).ToString()); break;
+                        default: writer.WriteNullValue(); break;
+                    };
+                    break;
+                case ArrowTypeId.Time64:
+                    Time64Array time64Array = (Time64Array)array;
+                    long time64 = time64Array.GetValue(index)!.Value;
+                    switch (((Time64Type)time64Array.Data.DataType).Unit)
+                    {
+                        case TimeUnit.Microsecond: writer.WriteStringValue(TimeSpan.FromTicks(time64 * 10).ToString()); break;
+                        case TimeUnit.Nanosecond: writer.WriteStringValue(TimeSpan.FromTicks(time64 / 100).ToString()); break;
+                        default: writer.WriteNullValue(); break;
+                    };
+                    break;
+#endif
+                case ArrowTypeId.Timestamp: writer.WriteStringValue(((TimestampArray)array).GetTimestamp(index)!.Value); break;
+                case ArrowTypeId.UInt8: writer.WriteNumberValue(((UInt8Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.UInt16: writer.WriteNumberValue(((UInt16Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.UInt32: writer.WriteNumberValue(((UInt32Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.UInt64: writer.WriteNumberValue(((UInt64Array)array).GetValue(index)!.Value); break;
+                case ArrowTypeId.Binary: writer.WriteBase64StringValue(((BinaryArray)array).GetBytes(index)); break;
+                default: writer.WriteNullValue(); break;
+            }
+        }
 
-        private static object ToListOrMap(ListArray listArray, int index)
+        private static void SerializeListOrMap(Utf8JsonWriter writer, ListArray listArray, int index)
         {
             IArrowArray values = listArray.Values;
             int start = (int)listArray.ValueOffsets[index];
             int end = (int)listArray.ValueOffsets[index + 1];
 
             // Arrow MAP is stored as List<Struct<key, value>>
             if (values is StructArray structValues && IsMapStruct(structValues))
-                return ToMapDict(structValues, start, end);
+            {
+                SerializeMapDict(writer, structValues, start, end);
+                return;
+            }
 
+            writer.WriteStartArray();
             List<object?> list = new List<object?>();
             for (int i = start; i < end; i++)
-                list.Add(ToObject(values, i));
-            return list;
+                SerializeStructuredValue(writer, values, i);
+            writer.WriteEndArray();
         }
 
         private static bool IsMapStruct(StructArray structArray)
@@ -232,28 +318,31 @@ private static bool IsMapStruct(StructArray structArray)
                    type.Fields[1].Name == "value";
         }
 
-        private static SortedDictionary<string, object?> ToMapDict(StructArray entries, int start, int end)
+        private static void SerializeMapDict(Utf8JsonWriter writer, StructArray entries, int start, int end)
         {
             IArrowArray keyArray = entries.Fields[0];
             IArrowArray valueArray = entries.Fields[1];
-            // Use SortedDictionary for deterministic key ordering in the JSON output
-            SortedDictionary<string, object?> result = new SortedDictionary<string, object?>();
+            writer.WriteStartObject();
             for (int i = start; i < end; i++)
             {
                 // Convert any key type to its string representation; treat null keys as "null"
-                string key = ToObject(keyArray, i)?.ToString() ?? "null";
-                result[key] = ToObject(valueArray, i);
+                string key = keyArray.ValueAt(i)?.ToString() ?? "null";
+                writer.WritePropertyName(key);
+                SerializeStructuredValue(writer, valueArray, i);
             }
-            return result;
+            writer.WriteEndObject();
         }
 
-        private static Dictionary<string, object?> ToDict(StructArray structArray, int index)
+        private static void SerializeDict(Utf8JsonWriter writer, StructArray structArray, int index)
         {
             StructType type = (StructType)structArray.Data.DataType;
-            Dictionary<string, object?> dict = new Dictionary<string, object?>();
+            writer.WriteStartObject();
             for (int i = 0; i < type.Fields.Count; i++)
-                dict[type.Fields[i].Name] = ToObject(structArray.Fields[i], index);
-            return dict;
+            {
+                writer.WritePropertyName(type.Fields[i].Name);
+                SerializeStructuredValue(writer, structArray.Fields[i], index);
+            }
+            writer.WriteEndObject();
         }
     }
 }

csharp/src/DatabricksConfigJsonContext.cs

@@ -0,0 +1,38 @@
+/*
+* Copyright (c) 2026 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.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AdbcDrivers.Databricks
+{
+    /// <summary>
+    /// System.Text.Json source-generated metadata for the free-form configuration file, which is
+    /// read as a flat <see cref="Dictionary{TKey,TValue}"/> of string-to-string. Using the
+    /// generated context keeps the deserialization trim- and NativeAOT-safe. The options mirror
+    /// the prior runtime options: case-insensitive property names, comments skipped, and trailing
+    /// commas allowed.
+    /// </summary>
+    [JsonSourceGenerationOptions(
+        PropertyNameCaseInsensitive = true,
+        ReadCommentHandling = JsonCommentHandling.Skip,
+        AllowTrailingCommas = true)]
+    [JsonSerializable(typeof(Dictionary<string, string>))]
+    internal partial class DatabricksConfigJsonContext : JsonSerializerContext
+    {
+    }
+}

csharp/src/DatabricksConfiguration.cs

@@ -81,15 +81,11 @@ public static DatabricksConfiguration FromFile(string filePath)
             try
             {
                 string json = File.ReadAllText(filePath);
-                var options = new JsonSerializerOptions
-                {
-                    PropertyNameCaseInsensitive = true,
-                    ReadCommentHandling = JsonCommentHandling.Skip,
-                    AllowTrailingCommas = true
-                };
 
-                // Deserialize as flat dictionary (free-form JSON)
-                var properties = JsonSerializer.Deserialize<Dictionary<string, string>>(json, options);
+                // Deserialize as flat dictionary (free-form JSON). The source-generated context
+                // (case-insensitive, comments skipped, trailing commas allowed) keeps this
+                // trim- and NativeAOT-safe.
+                var properties = JsonSerializer.Deserialize(json, DatabricksConfigJsonContext.Default.DictionaryStringString);
                 if (properties == null)
                 {
                     throw new InvalidOperationException($"Failed to deserialize configuration from {filePath}");

csharp/src/DatabricksStatement.cs

@@ -1104,7 +1104,7 @@ protected override async Task<QueryResult> GetColumnsExtendedAsync(CancellationT
                 {
                     throw new FormatException($"Invalid json result of {query}: result is null or empty");
                 }
-                var result = JsonSerializer.Deserialize<DescTableExtendedResult>(resultJson!);
+                var result = JsonSerializer.Deserialize(resultJson!, DescTableJsonContext.Default.DescTableExtendedResult);
                 if (result == null)
                 {
                     throw new FormatException($"Invalid json result of {query}.Result={resultJson}");