CSHARP-1198: fixed null reference bug in FindFluent.CountAsync.

Author: craiggwilson

src/MongoDB.Driver.Tests/FindFluentTests.cs

@@ -0,0 +1,61 @@
+/* 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.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using MongoDB.Bson;
+using NSubstitute;
+using NUnit.Framework;
+
+namespace MongoDB.Driver.Tests
+{
+    [TestFixture]
+    public class FindFluentTests
+    {
+        private IMongoCollection<Person> _collection;
+
+        [Test]
+        public void CountAsync_should_not_throw_a_null_reference_exception()
+        {
+            var subject = CreateSubject();
+
+            var result = subject.CountAsync().GetAwaiter().GetResult();
+
+            _collection.Received().CountAsync(
+                subject.Filter,
+                Arg.Any<CountOptions>(),
+                Arg.Any<CancellationToken>());
+        }
+
+        private IFindFluent<Person, Person> CreateSubject()
+        {
+            var settings = new MongoCollectionSettings();
+            _collection = Substitute.For<IMongoCollection<Person>>();
+            _collection.Settings.Returns(settings);
+            var options = new FindOptions<Person, Person>();
+            var subject = new FindFluent<Person, Person>(_collection, new BsonDocument(), options);
+
+            return subject;
+        }
+
+        public class Person
+        {
+            public string FirstName;
+            public string LastName;
+            public int Age;
+        }
+    }
+}

src/MongoDB.Driver.Tests/MongoDB.Driver.Tests.csproj

@@ -93,6 +93,7 @@
     </Compile>
     <Compile Include="BulkWriteErrorTests.cs" />
     <Compile Include="FieldDefinitionTests.cs" />
+    <Compile Include="FindFluentTests.cs" />
     <Compile Include="Linq\Translators\LegacyPredicateTranslatorTests.cs" />
     <Compile Include="Linq\Translators\TranslatorTestBase.cs" />
     <Compile Include="Linq\Translators\PredicateTranslatorTests.cs" />

src/MongoDB.Driver/FindFluent.cs

@@ -50,8 +50,11 @@ public override FindOptions<TDocument, TProjection> Options
         // methods
         public override Task<long> CountAsync(CancellationToken cancellationToken)
         {
-            BsonValue hint;
-            _options.Modifiers.TryGetValue("$hint", out hint);
+            BsonValue hint = null;
+            if (_options.Modifiers != null)
+            {
+                _options.Modifiers.TryGetValue("$hint", out hint);
+            }
             var options = new CountOptions
             {
                 Hint = hint,