Difference between Newtonsoft Json DynamicValueProvider and ReflectionValueProvider?

Question

I'm in the process of porting a Asp.Net Core Website targeting the full framework to a website that targets Asp.Net Core 3.

In that process I have hit a snag. The website references the Newtonsoft 11.0.3 NuGet package and among other things uses the Newtonsoft.Json.Serialization.DynamicValueProvider class.

Interestingly that class exists when targeting the full framework but does not exist when targeting netcoreapp3.1 and so Visual Studio is producing compilation errors stating that the class doesn't exist. At first that seemed crazy to me, but I checked the source code for the class and sure enough it contains the following conditional compilation statement wrapped around the whole class

#if HAVE_REFLECTION_EMIT

Apparently the netStandard 2.0 dll in the NuGet package that my netcoreapp3.1 project would use causes the conditional compilation statement to not include the DynamicValueProvider class.

So I did some poking around in the Newtonsoft.Json.Serialization namespace and I see that there is a ReflectionValueProvider class available that does not contain such conditional compilation and is available when targeting netcoreapp3.1

I've looked at the source code for both the DynamicValueProvider class and the ReflectionValueProvider class and I'm unclear on the difference. Both appear to get or set the value of a property or member type based on the MemberInfo passed in into the constructor. Both appear to use reflection to accomplish their work. As I mentioned, apparently DynamicValueProvider needs reflection Emit ability and ReflectionValueProvider does not. Emit ability apparently is used to Emit IL as best I can tell.

So I wonder if perhaps the two are drop in replacements for each other except that maybe DynamicValueProvider might be faster since it apparently leverages IL Emitting. But that's just a hunch. I'd prefer to have a more concrete understanding of the differences between the two classes before I start swapping the one for the other in this existing codebase as a way to get to .Net Core 3.

Can you provide me with better insight into the differences between the DynamicValueProvider class and the ReflectionValueProvider class, or at least confirm my hunch?

Answer 1

We had updated Newtonsoft.Json from 9.* to 12.0.3 version, and observed performance degradation on paths that includes json serialization. All paths lead to DynamicValueProvider. Fortunately, we had global descendant for DefaultContractResolver, and I was able to overload CreateMemberValueProvider method to return ReflectionValueProvider.

For now we are continue testing the new version, but I can say that from performance perspective ReflectionValueProvider works faster than DynamicValueProvider.