PerformantReflection

A super small library for making Reflection FAST.

The current version exposes Properties, allowing you to read their values as well as write new values with basically no performance penalty compared to when not using Reflection.

It has a sped-up version of the .Net built-in Activator.CreateInstance: TypeInstantiator.CreateInstance. This is archived by reflecting types just once, and emitting IL to create new dynamic methods. Finally a delegate is cached for these dynamic methods, and invoking these delegates has basically no performance penalty.

It also has an ObjectBuilder/InterfaceObjectBuilder for instantiating classes/interfaces and setting properties with private setters to some custom value. I personally use this for Fakes in integration tests, when Mocks don't cut it.

Finally there's the InterfaceImplementationGenerator which allows you to create implementation classes of interfaces on-the-fly. This can be quite useful for exchanging e.g. JSON based messages.

Installation

I recommend using the NuGet package: PerformantReflection however feel free to clone the source instead if that suits your needs better.

Usage

For properties

Simply instantiate an ObjectAccessor and feed it the object you want to access. Then you can loop over the Properties, index into them with ["PropertyName"] or use TryGetValue if you're unsure whether the property even exists:

Examples:

class User {
	public string Username { get;set; }
}

var user = new User {
	Username = "Old username"
};

var accessor = new ObjectAccessor(user);

var existingUsername = accessor.Properties["Username"].GetValue();

accessor.Properties["Username"].SetValue("New username");

For instantiating types

Simply call TypeInstantiator.CreateInstance(someType) similar to how you would with Activator.CreateInstance - it's that simple :-)

Or if you need to populate properties with public getters but private setters, use the ObjectBuilder like this:

var instance = new ObjectBuilder<YourType>()
                .With(inst => inst.Id, Guid.NewGuid()) // The Id property will be set to Guid.NewGuid()
                .With(inst => inst.Name, "Some name") // Likewise Name will be set to "Some name"
                .Build();

For iterating over properties of types

Use the TypePropertyCache to get a collection of properties for any given type. As the name implies this information is cached for rapid repeated lookup. Furthermore the resulting type PropertyInformation holds high-performance getter and setter methods (assuming the property in question has a getter or setter)

For generating implementation types based on interfaces

Simply call InterfaceImplementationGenerator.GenerateImplementationType<T> or CreateInstance<T> depending on your needs. This will generate an implementation type for the interface (and instantiate an instance if calling CreateInstance<T>).

This can be quite useful when sending e.g. JSON serialized messages where you don't want to share the implementation class, but rather just the interface. It can also be useful for situations where your class has private setters and you want to maintain that. Simply specify an interface with only the getters, and use GenerateImplementationType<T> to implement a class with a public setter that allows you to deserialize the JSON, yet doesn't allow the caller to mutate the resulting instance.

Furthermore if you want to build an instance of your interface, with predefined values (quite useful for unit testing), use the InterfaceObjectBuilder in the same fashion as the "ordinary" ObjectBuilder:

var instance = new InterfaceObjectBuilder<IYourInterface>()
                .With(inst => inst.Id, Guid.NewGuid()) // The Id property will be set to Guid.NewGuid()
                .With(inst => inst.Name, "Some name") // Likewise Name will be set to "Some name"
                .Build();

For Json deserialization of properties with private setters

Either use the JsonSerializerOptionsFactory class to create a new JsonSerializerOptions instance with the necessary configuration, or use the extension method AddPrivateDeserializationSupport of JsonSerializerOptions to configure an existing options instance. Both reside in the PerformantReflection.Json namespace.

An example:

public class User
{
    public Guid Id { get; private set; }
    
    public User()
    {
        Id = Guid.NewGuid();
    }
}

var user = new User();
var json = JsonSerializer.Serialize(user);

var options = JsonSerializerOptionsFactory.CreateOptionsWithPrivateDeserializationSupport();
var deserialized = JsonSerializer.Deserialize<User>(json, options);

// deserialized will have the Id deserialized as well now

Documentation

Auto generated documentation via DocFx is available here: https://steffenskov.github.io/PerformantReflection/