IGNITE-16355 .NET: Support value types in the Table API (#1190)

* Remove `where T : class` constraint from all APIs.
* Use `Option<T>` as a return type for APIs which can return "no value" results, such as `Get`, `GetAndUpsert`, `GetAndDelete`.
    * It is not possible to handle nullable value and reference types in a generic way, so we have to use a common wrapper. `Option<T>` also clearly indicates which APIs always return something and which don't.
* Fix `ObjectSerializerHandler` to support value types.

modules/platforms/dotnet/Apache.Ignite.Tests/Compute/ComputeTests.cs

@@ -226,9 +226,13 @@ public async Task TestExecuteColocated(long key, string nodeName)
             var keyPoco = new Poco { Key = key };
             var resNodeName2 = await Client.Compute.ExecuteColocatedAsync<string, Poco>(TableName, keyPoco, NodeNameJob);
 
+            var keyPocoStruct = new PocoStruct(key, null);
+            var resNodeName3 = await Client.Compute.ExecuteColocatedAsync<string, PocoStruct>(TableName, keyPocoStruct, NodeNameJob);
+
             var expectedNodeName = PlatformTestNodeRunner + nodeName;
             Assert.AreEqual(expectedNodeName, resNodeName);
             Assert.AreEqual(expectedNodeName, resNodeName2);
+            Assert.AreEqual(expectedNodeName, resNodeName3);
         }
 
         [Test]

modules/platforms/dotnet/Apache.Ignite.Tests/OptionTests.cs

@@ -0,0 +1,105 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+namespace Apache.Ignite.Tests;
+
+using System;
+using NUnit.Framework;
+
+/// <summary>
+/// Tests for <see cref="Option{T}"/>.
+/// </summary>
+public sealed class OptionTests
+{
+    [Test]
+    public void TestDefaultValueEqualsNone()
+    {
+        Assert.AreEqual(default(Option<int>), Option.None<int>());
+        Assert.IsTrue(Option.None<int>() == default);
+
+        Assert.AreEqual(default(Option<string>), Option.None<string>());
+        Assert.IsTrue(Option.None<string>() == default);
+    }
+
+    [Test]
+    public void TestNoneValueThrows()
+    {
+        var ex = Assert.Throws<InvalidOperationException>(() =>
+        {
+            _ = Option.None<int>().Value;
+        });
+
+        Assert.AreEqual("Value is not present. Check HasValue property before accessing Value.", ex!.Message);
+    }
+
+    [Test]
+    public void TestEquality()
+    {
+        Assert.AreEqual(Option.Some(123), (Option<int>)123);
+        Assert.AreNotEqual(Option.Some(123), Option.Some(124));
+    }
+
+    [Test]
+    public void TestSomeReferenceTypeDeconstruct()
+    {
+        var (val, hasVal) = Option.Some("abc");
+
+        Assert.IsTrue(hasVal);
+        Assert.AreEqual("abc", val);
+    }
+
+    [Test]
+    public void TestNoneReferenceTypeDeconstruct()
+    {
+        var (val, hasVal) = Option.None<string>();
+
+        Assert.IsFalse(hasVal);
+        Assert.IsNull(val);
+    }
+
+    [Test]
+    public void TestSomeValueTypeDeconstruct()
+    {
+        var (val, hasVal) = Option.Some(123L);
+
+        Assert.IsTrue(hasVal);
+        Assert.AreEqual(123L, val);
+    }
+
+    [Test]
+    public void TestNoneValueTypeDeconstruct()
+    {
+        var (val, hasVal) = Option.None<long>();
+
+        Assert.IsFalse(hasVal);
+        Assert.AreEqual(0L, val);
+    }
+
+    [Test]
+    public void TestNoneToString()
+    {
+        Assert.AreEqual("Option { HasValue = False }", Option.None<int>().ToString());
+        Assert.AreEqual("Option { HasValue = False }", Option.None<string>().ToString());
+    }
+
+    [Test]
+    public void TestSomeToString()
+    {
+        Assert.AreEqual("Option { HasValue = True, Value = 123 }", Option.Some(123).ToString());
+        Assert.AreEqual("Option { HasValue = True, Value = Foo }", Option.Some("Foo").ToString());
+    }
+}

modules/platforms/dotnet/Apache.Ignite.Tests/Sql/SqlTests.cs

@@ -168,7 +168,7 @@ public async Task TestPutSqlGetKv()
             var table = await Client.Tables.GetTableAsync("TEST");
             var res = await table!.RecordBinaryView.GetAsync(null, new IgniteTuple { ["ID"] = 1 });
 
-            Assert.AreEqual("s-1", res!["VAL"]);
+            Assert.AreEqual("s-1", res.Value["VAL"]);
         }
 
         [Test]

modules/platforms/dotnet/Apache.Ignite.Tests/Table/PocoStruct.cs

@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+namespace Apache.Ignite.Tests.Table;
+
+/// <summary>
+/// Test user struct.
+/// </summary>
+public record struct PocoStruct(long Key, string? Val, string? UnmappedStr = null);