Loading .Net libraries in Node Js

This is a native nodejs extension which allows us to load dot-net assemblies, create objects and call methods on them.

Based upon

saary's node.net and v8sharp

The interface

Instantiate the module, load a dll and create a class. Currently it searches the active directory of the node process for assemblies.

var sharp = require('./Sharp').Sharp();
var stub = sharp.load('StubClass.dll');
var oc = stub.new('StubClass.Output');

Then the class exposes all methods for synchronous and asynchronous callbacks.

var list = oc.call('ReturnList');
// list = [17, 6, 81]  // some random set of integers

oc.async('ReturnObject', function(err, data){ 
    console.dir(data); 
});

There is also a .methods() call to return a list of callable method names.

You can call constructors and access static methods now too.

var constructed = stub.new('StubClass.Constructor', 1, "string");

var st = stub.static('StubClass.Static');
st.methods(); // list all static methods
var val = st.call('GetString');

What is it for?

Some of the linked resources from node.net, and research on the subject will tell you that C++/CLI has a performance hit in node over native javascript. This add-on uses System.Reflection for most operations, and additional marshaling into managed types which further add to the cost. So in short - your production system probably shouldn't rely on this path. It is intended for prototyping, when you already have classes to do what you want in C#. And the same advice as native modules apply - if your calls are long and async, then the costs of transforming the data are a smaller fraction.

Things that work

• Listing dlls in the current directory
• Loading managed assemblies (doesn't have to be .dll, loading Sharp.node has all the fun generated internals)
• Call zero argument constructors
• Calling methods where types can be converted

Speaking of - type conversion (mostly inherited from v8sharp)

• string
• int
• date -> datetime
• arrays -> typed arrays and lists
• object -> dictionary of string and objects, and objects with public properties.
• returned objects are returned

What's next?

From the previous list, there are many things which could be added to make the process a little more seamless.

• access to fields
• overloaded methods (honestly, this is hard when you're not a compiler)
• also playing with node-gyp and npm to get the build install to be more streamlined.