Expresharp - Express on .NET

Expresharp is a single file that can be drop in to your project and enable coding like Express.js for web application.

Express.js is a:

Fast, unopinionated, minimalist web framework for node.

Have fun!

var app = new Express();

app.Get("/", (req, res) => res.Send("Hello World!"));

var server = app.Listen(3000);

Getting started

Installation

Expresharp is available on NuGet.

PM> Install-Package Expresharp

Hello world

Here is an example of a very basic Express app. It starts a server and listens on port 3000 for connection. It will respond with “Hello World!” for requests to the homepage. For every other path, it will respond with a 404 Not Found.

view code

using System;
using System.Linq;
using Expresharp;

class Program
{
  static void Main(string[] args)
  {
    var app = new Express();
    
    app.Get("/", (req, res) => res.Send("Hello World!"));
    
    var server = app.Listen(3000);
    
    Console.WriteLine("Example app listening at {0}.", server.Prefixes.First());
    Console.WriteLine("Press ENTER to exit.");
    Console.ReadLine();
  }
}

Basic routing

Routing refers to determining how an application responds to a client request to a particular endpoint, which is a URI (or path) and a specific HTTP request method (GET, POST, and so on). Each route can have one or more handler functions, which is / are executed when the route is matched.

view code

// respond with "Hello World!" on the homepage
app.Get("/", (req, res) => res.Send("Hello World!"));

// accept POST request on the homepage
app.Post("/", (req, res) => res.Send("Got a POST request"));

// accept PUT request at /user
app.Put("/user", (req, res) => res.Send("Got a PUT request at /user"));

// accept DELETE request at /user
app.Delete("/user", (req, res) => res.Send("Got a DELETE request at /user"));

Serving static files

Serving files, such as images, CSS, JavaScript and other static files is accomplished with the help of a built-in middleware - Express.Static.

view code

app.Use(Express.Static("public"));

Now, you will be able to load the files under the public directory:

http://localhost:3000/css/style.css
http://localhost:3000/js/app.js
http://localhost:3000/hello.html

By specifying a mount path for the static directory, as shown below, you can create a "virtual" path prefix for those files.

app.Use("/static", Express.Static("public"));

Now, you will be able to load the files under the public directory, from the path prefix "/static".

http://localhost:3000/static/css/style.css
http://localhost:3000/static/js/app.js
http://localhost:3000/static/hello.html

For more docs please refer to Guide or API reference on Express.js website.

WebSocket

Expresharp.Fleck is a middleware of Express which enables WebSocket ability by Fleck.

Installation

Expresharp.Fleck is available on NuGet.

PM> Install-Package Expresharp.Fleck

Usage

view code

It's easy to add WebSocket handler to a specified path or globally with extension methods.

app.WebSocket("/echo", ws =>
{
  ws.OnOpen = () => Console.WriteLine("Opened");
  ws.OnClose = () => Console.WriteLine("Closed");
  ws.OnError = e => Console.WriteLine("Error: {0}", e);
  ws.OnMessage = msg =>
  {
    Console.WriteLine("Received: {0}", msg);
    ws.Send("Echo: " + msg);
  };
});

Or create an instance of the WebSocketMiddleware for reuse:

var echo = new WebSocketMiddleware();

echo.OnConnection(ws =>
{
  ws.OnOpen = () => Console.WriteLine("Opened");
  ws.OnClose = () => Console.WriteLine("Closed");
  ws.OnError = e => Console.WriteLine("Error: {0}", e);
  ws.OnMessage = msg =>
  {
    Console.WriteLine("Received: {0}", msg);
    ws.Send("Echo: " + msg);
  };
});

app.Use("/echo", echo);
app.Use("/chat", echo);

Note

The System.Net.HttpListener inside Expresharp accepts WebSocket connections only on .NET 4.5+ and Windows 8+ [[1]] (https://connect.microsoft.com/VisualStudio/feedback/details/672604/websocket-support-missing-from-http-sys). For other platforms, a better choice is to adapt Expresharp to a 3rd party or your own HTTP server. Check out next section and Custom HTTP server example for more.

Custom HTTP server

Instead of System.Net.HttpListener, you may like to customize your own HTTP server. This is quite simple with Expresharp.

There are two interfaces in your concern: IHttpRequest and IHttpResponse. Whenever you like, wrap your requests/responses as these two interfaces, push them into an Expresharp app, and let Express take care of the rest.

view code

class CustomHttpRequest : IHttpRequest { }
class CustomHttpResponse : IHttpResponse { }

// here comes your request/response, wrap them up!
var req = new CustomHttpRequest(request);
var res = new CustomHttpResponse(response);

// push req/res into the Express app, and that's all :)
app.Handle(req, res, null);

The last parameter of app.Handle(IHttpRequest, IHttpResponse, Next) is a handler that will receive all requests not consumed by any route, such as errors and 404s. For most cases, a null is enough.

License

MIT