CSHARP-674: Handle null keys as well as null values in KeyValuePairSerializer.

Author: Robert Stam

MongoDB.Bson/Serialization/Serializers/KeyValuePairSerializer.cs

@@ -166,17 +166,11 @@ public override void Serialize(
             var keyValuePair = (KeyValuePair<TKey, TValue>)value;
             var keyValuePairSerializationOptions = EnsureSerializationOptions<KeyValuePairSerializationOptions>(options);
 
-            var keySerializer = GetKeySerializer(keyValuePair.Key.GetType());
-            
-            IBsonSerializer valueSerializer;
-            if (null == keyValuePair.Value)
-            {
-                valueSerializer = GetValueSerializer(typeof(object));
-            }
-            else
-            {
-                valueSerializer = GetValueSerializer(keyValuePair.Value.GetType());
-            }
+            var keyType = (keyValuePair.Key == null) ? typeof(TKey) : keyValuePair.Key.GetType();
+            var keySerializer = GetKeySerializer(keyType);
+            var valueType = (keyValuePair.Value == null) ? typeof(TValue) : keyValuePair.Value.GetType();
+            var valueSerializer = GetValueSerializer(valueType);
+
             switch (keyValuePairSerializationOptions.Representation)
             {
                 case BsonType.Array:

MongoDB.BsonUnitTests/MongoDB.BsonUnitTests.csproj

@@ -113,6 +113,7 @@
     <Compile Include="Serialization\LegacyBsonClassMapTests.cs" />
     <Compile Include="Serialization\Serializers\ExtraElementsTests.cs" />
     <Compile Include="Serialization\Options\RepresentationSerializationOptionsTests.cs" />
+    <Compile Include="Serialization\Serializers\KeyValuePairSerializerTests.cs" />
     <Compile Include="Serialization\Serializers\SerializeFlagsTests.cs" />
     <Compile Include="Serialization\Serializers\AnimalHierarchyWithAttributesTests.cs" />
     <Compile Include="Serialization\Serializers\AnimalHierarchyWithoutAttributesTests.cs" />
@@ -241,4 +242,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>

MongoDB.BsonUnitTests/Serialization/Serializers/KeyValuePairSerializerTests.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2012 10gen Inc.
+/* Copyright 2010-2013 10gen Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -13,29 +13,36 @@
 * limitations under the License.
 */
 
-using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
-using System.Text;
-using NUnit.Framework;
-
 using MongoDB.Bson;
-using MongoDB.Bson.IO;
 using MongoDB.Bson.Serialization;
-using MongoDB.Bson.Serialization.Attributes;
+using NUnit.Framework;
 
 namespace MongoDB.BsonUnitTests.DefaultSerializer.Serializers
 {
     [TestFixture]
     public class KeyValuePairSerializerTests
     {
+        [Test]
+        public void TestNullKey()
+        {
+            var kvp = new KeyValuePair<string, object>(null, "value");
+            var json = kvp.ToJson();
+            var expected = "{ 'k' : null, 'v' : 'value' }".Replace("'", "\"");
+            Assert.AreEqual(expected, json);
+
+            var bson = kvp.ToBson();
+            var rehydrated = BsonSerializer.Deserialize<KeyValuePair<string, object>>(bson);
+            Assert.IsTrue(bson.SequenceEqual(rehydrated.ToBson()));
+        }
+
         [Test]
         public void TestNullValue()
         {
-            KeyValuePair<string, object> kvp = new KeyValuePair<string, object>("Value", null);
+            var kvp = new KeyValuePair<string, object>("key", null);
             var json = kvp.ToJson();
-            var expected = "{ 'k' : 'Value', 'v' : null }".Replace("'", "\"");
+            var expected = "{ 'k' : 'key', 'v' : null }".Replace("'", "\"");
             Assert.AreEqual(expected, json);
 
             var bson = kvp.ToBson();