added support for upcasting in linq.

Author: craiggwilson

Driver/Linq/Utils/BsonSerializationInfoHelper.cs

@@ -69,11 +69,7 @@ public BsonSerializationInfo GetSerializationInfo(Expression expression)
                     _serializerCache[parameterExpression] = serializer;
                 }
 
-                return new BsonSerializationInfo(
-                    null, // elementName
-                    serializer,
-                    parameterExpression.Type, // nominalType
-                    null); // serialization options
+                return GetSerializationInfo(serializer, expression);
             }
 
             parameterExpression = ExpressionParameterFinder.FindParameter(expression);
@@ -170,11 +166,24 @@ public BsonArray SerializeValues(BsonSerializationInfo serializationInfo, IEnume
 
         private BsonSerializationInfo GetSerializationInfo(IBsonSerializer serializer, Expression expression)
         {
-            // when looking to get a member's serialization info, we will ignore a top-level return conversion because 
-            // it is inconsequential
+            var parameterExpression = expression as ParameterExpression;
+            if (parameterExpression != null)
+            {
+                return new BsonSerializationInfo(
+                    null,
+                    serializer,
+                    parameterExpression.Type,
+                    null);
+            }
+
             if (expression.NodeType == ExpressionType.Convert || expression.NodeType == ExpressionType.ConvertChecked)
             {
-                return GetSerializationInfo(serializer, ((UnaryExpression)expression).Operand);
+                var conversionSerializer = serializer;
+
+                //if the operand can be assigned from the expression, than we are upcasting and need to get the more specific serializer
+                if (((UnaryExpression)expression).Operand.Type.IsAssignableFrom(expression.Type))
+                    conversionSerializer = BsonSerializer.LookupSerializer(expression.Type);
+                return GetSerializationInfo(conversionSerializer, ((UnaryExpression)expression).Operand);
             }
 
             var memberExpression = expression as MemberExpression;
@@ -316,8 +325,11 @@ private BsonSerializationInfo GetSerializationInfoMember(IBsonSerializer seriali
                 if (memberSerializationInfoProvider != null)
                 {
                     var memberSerializationInfo = memberSerializationInfoProvider.GetMemberSerializationInfo(memberName);
+                    var elementName = memberSerializationInfo.ElementName;
+                    if (!string.IsNullOrEmpty(containingSerializationInfo.ElementName))
+                        elementName = containingSerializationInfo.ElementName + "." + elementName;
                     return new BsonSerializationInfo(
-                        containingSerializationInfo.ElementName + "." + memberSerializationInfo.ElementName,
+                        elementName,
                         memberSerializationInfo.Serializer,
                         memberSerializationInfo.NominalType,
                         memberSerializationInfo.SerializationOptions);

DriverUnitTests/DriverUnitTests.csproj

@@ -164,6 +164,7 @@
     <Compile Include="Jira\CSharp365Tests.cs" />
     <Compile Include="Jira\CSharp378Tests.cs" />
     <Compile Include="Jira\CSharp418Tests.cs" />
+    <Compile Include="Jira\CSharp471Tests.cs" />
     <Compile Include="Jira\CSharp77Tests.cs" />
     <Compile Include="Jira\CSharp92Tests.cs" />
     <Compile Include="Jira\CSharp93Tests.cs" />

DriverUnitTests/Jira/CSharp471Tests.cs

@@ -0,0 +1,86 @@
+/* Copyright 2010-2012 10gen 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.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using NUnit.Framework;
+
+using MongoDB.Driver;
+using MongoDB.Driver.Linq;
+
+namespace MongoDB.DriverUnitTests.Jira
+{
+    [TestFixture]
+    public class CSharp471Tests
+    {
+        public class Base
+        {
+            public Guid Id { get; set; }
+
+            public string A { get; set; }
+        }
+
+        public class T1 : Base
+        {
+            public string B { get; set; }
+        }
+
+        public class T2 : Base
+        {
+            public string C { get; set; }
+        }
+
+        [Test]
+        public void CastTest()
+        {
+            var server = MongoServer.Create();
+            var db = server.GetDatabase("test");
+            var collection = db.GetCollection<Base>("castTest");
+            collection.Drop();
+
+            var t1 = new T1 { Id = Guid.NewGuid(), A = "T1.A", B = "T1.B" };
+            var t2 = new T2 { Id = Guid.NewGuid(), A = "T2.A" };
+            collection.Insert(t1);
+            collection.Insert(t2);
+
+            var query = from t in collection.AsQueryable()
+                        where t is T1 && ((T1)t).B == "T1.B" 
+                        select t;
+
+            var translatedQuery = MongoQueryTranslator.Translate(query);
+            Assert.IsInstanceOf<SelectQuery>(translatedQuery);
+            Assert.AreSame(collection, translatedQuery.Collection);
+            Assert.AreSame(typeof(Base), translatedQuery.DocumentType);
+
+            var selectQuery = (SelectQuery)translatedQuery;
+            Assert.AreEqual("(Base t) => ((t is T1) && ((T1)t.B == \"T1.B\"))", ExpressionFormatter.ToString(selectQuery.Where));
+            Assert.IsNull(selectQuery.OrderBy);
+            Assert.IsNull(selectQuery.Projection);
+            Assert.IsNull(selectQuery.Skip);
+            Assert.IsNull(selectQuery.Take);
+
+            Assert.AreEqual("{ \"_t\" : \"T1\", \"B\" : \"T1.B\" }", selectQuery.BuildQuery().ToString());
+
+            var results = query.ToList();
+            Assert.That(results.Count, Is.EqualTo(1));
+            Assert.That(results[0], Is.InstanceOf(typeof(T1)));
+            Assert.That(results[0].A, Is.EqualTo("T1.A"));
+        }
+    }
+}