Fix BsonReader reading multiple content (#1870)

Src/Newtonsoft.Json.Tests/Bson/BsonReaderTests.cs

@@ -69,6 +69,53 @@ namespace Newtonsoft.Json.Tests.Bson
             Assert.AreEqual("1", (string)o["$id"]);
         }
 
+        public class MyTest
+        {
+            public DateTime TimeStamp { get; set; }
+            public string UserName { get; set; }
+            public MemoryStream Blob { get; set; }
+        }
+
+        [Test]
+        public void Bson_SupportMultipleContent()
+        {
+            MemoryStream myStream = new MemoryStream();
+            BsonWriter writer = new BsonWriter(myStream);
+            JsonSerializer serializer = new JsonSerializer();
+            MyTest tst1 = new MyTest
+            {
+                TimeStamp = new DateTime(2000, 12, 20, 12, 59, 59, DateTimeKind.Utc),
+                UserName = "Joe Doe"
+            };
+            MyTest tst2 = new MyTest
+            {
+                TimeStamp = new DateTime(2010, 12, 20, 12, 59, 59, DateTimeKind.Utc),
+                UserName = "Bob"
+            };
+            serializer.Serialize(writer, tst1);
+            serializer.Serialize(writer, tst2);
+
+            myStream.Seek(0, SeekOrigin.Begin);
+
+            BsonReader reader = new BsonReader(myStream)
+            {
+                SupportMultipleContent = true,
+                DateTimeKindHandling = DateTimeKind.Utc
+            };
+
+            MyTest tst1A = serializer.Deserialize<MyTest>(reader);
+
+            reader.Read();
+
+            MyTest tst2A = serializer.Deserialize<MyTest>(reader);
+
+            Assert.AreEqual(tst1.UserName, tst1A.UserName);
+            Assert.AreEqual(tst1.TimeStamp, tst1A.TimeStamp);
+
+            Assert.AreEqual(tst2.UserName, tst2A.UserName);
+            Assert.AreEqual(tst2.TimeStamp, tst2A.TimeStamp);
+        }
+
         [Test]
         public void CloseInput()
         {

Src/Newtonsoft.Json/Bson/BsonReader.cs

@@ -370,6 +370,11 @@ namespace Newtonsoft.Json.Bson
                     ContainerContext context = _currentContext;
                     if (context == null)
                     {
+                        if (SupportMultipleContent)
+                        {
+                            goto case State.Start;
+                        }
+
                         return false;
                     }