Added support for Distinct<TValue>.

Author: rstam

MongoDB.Driver/MongoCollection.cs

@@ -256,6 +256,54 @@ public virtual IEnumerable<BsonValue> Distinct(string key, IMongoQuery query)
             return result.Response["values"].AsBsonArray;
         }
 
+        /// <summary>
+        /// Returns the distinct values for a given field.
+        /// </summary>
+        /// <typeparam name="TValue">The type of the value.</typeparam>
+        /// <param name="key">The key of the field.</param>
+        /// <returns>The distint values of the field.</returns>
+        public virtual IEnumerable<TValue> Distinct<TValue>(string key)
+        {
+            return Distinct<TValue>(key, Query.Null);
+        }
+
+        /// <summary>
+        /// Returns the distinct values for a given field for documents that match a query.
+        /// </summary>
+        /// <typeparam name="TValue">The type of the value.</typeparam>
+        /// <param name="key">The key of the field.</param>
+        /// <param name="query">The query (usually a QueryDocument or constructed using the Query builder).</param>
+        /// <returns>The distint values of the field.</returns>
+        public virtual IEnumerable<TValue> Distinct<TValue>(string key, IMongoQuery query)
+        {
+            var command = new CommandDocument
+            {
+                { "distinct", _name },
+                { "key", key },
+                { "query", BsonDocumentWrapper.Create(query), query != null } // query is optional
+            };
+            var result = RunCommand(command);
+
+            using (var bsonReader = BsonReader.Create(result.Response))
+            {
+                var serializer = BsonSerializer.LookupSerializer(typeof(TValue));
+                bsonReader.ReadStartDocument();
+                if (bsonReader.FindElement("values"))
+                {
+                    bsonReader.ReadStartArray();
+                    while (bsonReader.ReadBsonType() != BsonType.EndOfDocument)
+                    {
+                        yield return (TValue)serializer.Deserialize(bsonReader, typeof(TValue), null);
+                    }
+                    bsonReader.ReadEndArray();
+                }
+                else
+                {
+                    throw new FormatException("Command Response is missing the values element.");
+                }
+            }
+        }
+
         /// <summary>
         /// Drops this collection.
         /// </summary>

MongoDB.DriverUnitTests/MongoCollectionTests.cs

@@ -240,6 +240,23 @@ public void TestDistinct()
             Assert.AreEqual(false, values.Contains(4));
         }
 
+        [Test]
+        public void TestDistinct_Typed()
+        {
+            _collection.RemoveAll();
+            _collection.DropAllIndexes();
+            _collection.Insert(new BsonDocument("x", 1));
+            _collection.Insert(new BsonDocument("x", 2));
+            _collection.Insert(new BsonDocument("x", 3));
+            _collection.Insert(new BsonDocument("x", 3));
+            var values = new HashSet<int>(_collection.Distinct<int>("x"));
+            Assert.AreEqual(3, values.Count);
+            Assert.AreEqual(true, values.Contains(1));
+            Assert.AreEqual(true, values.Contains(2));
+            Assert.AreEqual(true, values.Contains(3));
+            Assert.AreEqual(false, values.Contains(4));
+        }
+
         [Test]
         public void TestDistinctWithQuery()
         {
@@ -258,6 +275,24 @@ public void TestDistinctWithQuery()
             Assert.AreEqual(false, values.Contains(4));
         }
 
+        [Test]
+        public void TestDistinctWithQuery_Typed()
+        {
+            _collection.RemoveAll();
+            _collection.DropAllIndexes();
+            _collection.Insert(new BsonDocument("x", 1));
+            _collection.Insert(new BsonDocument("x", 2));
+            _collection.Insert(new BsonDocument("x", 3));
+            _collection.Insert(new BsonDocument("x", 3));
+            var query = Query.LTE("x", 2);
+            var values = new HashSet<int>(_collection.Distinct<int>("x", query));
+            Assert.AreEqual(2, values.Count);
+            Assert.AreEqual(true, values.Contains(1));
+            Assert.AreEqual(true, values.Contains(2));
+            Assert.AreEqual(false, values.Contains(3));
+            Assert.AreEqual(false, values.Contains(4));
+        }
+
         [Test]
         public void TestDropAllIndexes()
         {