CSHARP-958: Fix AssignId when nominal type is an interface.

Author: rstam

MongoDB.Driver/MongoCollection.cs

@@ -2173,12 +2173,13 @@ internal AggregateResult RunAggregateCommand(AggregateArgs args)
         // private methods
         private void AssignId(InsertRequest request)
         {
-            var serializer = request.Serializer ?? BsonSerializer.LookupSerializer(request.NominalType);
-            var idProvider = serializer as IBsonIdProvider;
-            if (idProvider != null)
+            var document = request.Document;
+            if (document != null)
             {
-                var document = request.Document;
-                if (document != null)
+                var actualType = document.GetType();
+                var serializer = request.Serializer ?? BsonSerializer.LookupSerializer(actualType);
+                var idProvider = serializer as IBsonIdProvider;
+                if (idProvider != null)
                 {
                     object id;
                     Type idNominalType;

MongoDB.DriverUnitTests/Jira/CSharp958Tests.cs

@@ -0,0 +1,46 @@
+/* Copyright 2010-2014 MongoDB Inc.
+*
+* 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;
+using System.Linq;
+using MongoDB.Bson;
+using MongoDB.Driver;
+using NUnit.Framework;
+
+namespace MongoDB.DriverUnitTests.Jira
+{
+    [TestFixture]
+    public class CSharp958Tests
+    {
+        private interface IPerson { }
+
+        private class Person : IPerson
+        {
+            public ObjectId Id { get; set; }
+            public string Name { get; set; }
+        }
+
+        [Test]
+        public void TestAssignIdWorksWithInterface()
+        {
+            var collection = Configuration.GetTestCollection<IPerson>();
+            collection.Drop();
+
+            IPerson person = new Person { Name = "Jack" };
+            var result = collection.Insert(person);
+            Assert.AreNotEqual(ObjectId.Empty, ((Person)person).Id);
+        }
+    }
+}

MongoDB.DriverUnitTests/MongoDB.DriverUnitTests.csproj

@@ -139,6 +139,7 @@
     <Compile Include="Jira\CSharp801Tests.cs" />
     <Compile Include="Jira\CSharp840Tests.cs" />
     <Compile Include="Jira\CSharp893Tests.cs" />
+    <Compile Include="Jira\CSharp958Tests.cs" />
     <Compile Include="Linq\BsonDocumentBackedClassSerializerTests.cs" />
     <Compile Include="Linq\BsonDocumentTests.cs" />
     <Compile Include="FailPoint.cs" />