README.md

Runtime Types

What is it

This library tries to simplify the runtime type creation by adding new things like the ability to define methods using Expressions and automatic interface implementation. It's a part of Detached.Mappers library. Thanks to the people who made FastExpressionCompiler, that is the core of this library.

What does it solve

It allows devs to create tools like dynamic proxies, comparers, dirty check (INotifyPropertyChange) or any other thing that may be a good fit for dynamic code without having to manually emit op codes. Methods can be defined using Expression trees.

How it works

Lets say that we want to dinamically create a type for this interface:

 public interface ISumService
 {
     int Sum(int a, int b);
 }

Then we need to intialize a type builder, define an implementation for Sum method using an expression tree, and call AutoImplementInterface to perform the override.

// create a type builder, this will handle the creation of a new Type.
RuntimeTypeBuilder typeBuilder = new RuntimeTypeBuilder("MyISumServiceImplementation", typeof(BasePropertyClass));

// define the parameters expected by the interface method.
var aParam = Parameter(typeof(int), "a");
var bParam = Parameter(typeof(int), "b");

// define a mehtod with the same signature (name and parameters),
// use "Add" expression as the method body
typeBuilder.DefineMethod(
    "Sum",
        new[] { aParam, bParam },
        Block(
        Add(aParam, bParam)
        )
);
            
// implement the interface, this will iterate over all methods and 
// call DefineMethodOverride to bind the existing methods to the given 
// interface methods
typeBuilder.AutoImplementInterface(typeof(ISumService));

// create the type that will be used to initialize new instances of ISumService
Type myISumServiceType = typeBuilder.Create();

// create an instance of our dynamic ISumService implementation
ISumService myISumService = (ISumService)Activator.CreateInstance(myISumServiceType);

// test the implementation
Assert.Equal(14, myISumService.Sum(5, 9));

More info and examples will be added later. Check unit tests for more samples!