I will make my first Linux web application in Microsoft’s “.net” platform. Since I do not run Windows I am going to using Mono (“.net for Linux”) and the MonoDevelop IDE. I am not so much a fan of ASP.net, so I’ve chosen Nancy instead which is a light-weight and simple replacement of ASP.net.
Nancy is a lightweight web framework for the .Net platform, inspired by Sinatra. Nancy aims at delivering a low ceremony approach to building light, fast web applications.
Xamarin is the company that allows for cross-platform multi-target (iOS, Android, Mac & Windows) development in C#. They maintain a recent build of the MonoDevelop application (currently 5.5). This tutorial may either be used for programming in C# or VB.net on Linux. C# does have support for code completion, something VB.net is missing in MonoDevelop.
To install the Xamarin version we have to add the Xamarin key and the repository by executing the following commands in any Debian based Linux (like Ubuntu/Mint):
sudo apt-key adv --keyserver pgp.mit.edu --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list sudo apt-get update
After that we can install everything using the following one-liner:
sudo apt-get install monodoc-base monodevelop mono-vbnc
Creating the project
After these installs (takes about 200 MB) you will have the “MonoDevelop” application (version 5.5) installed and you can start it from the “Development” menu. When you start it, it will ask you what you want to do. Choose to create an “Empty Project (VBNet)”. If you want to use C# then choose “Empty Project (C#)”.
If you get an error stating “Error while trying to load the project”, “Project does not support framework ‘.NETFramework,Version=v4.5′”, then you may want to open the project XML file (either “test.vbproj” or “test.csproj”) and replace the value that is defined as the “TargetFrameworkVersion”:
<TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
becomes:
<TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
You can see below how that looks in my MonoDevelop:
And then we can go look for Nancy.Hosting.Self via Project > Add Packages
When the “Add packages” window opens type “Nancy.Hosting.Self” in the search field:
Select the package and click “Add Package” to add it to your project. Great! Now it is time for some code.
Nancy’s Hello World example
First we make sure we start our host. In the Application.vb file.
Option Explicit On
Option Strict On
Imports System
Public Class Application
Public Shared Sub Main()
Dim host As Nancy.Hosting.Self.NancyHost
host = New Nancy.Hosting.Self.NancyHost(New Uri("http://localhost:8080"))
host.Start()
Console.ReadLine()
End Sub
End Class
And then we create a new Class “HelloModule” and add this code to it.
Option Explicit On
Option Strict On
Imports System
Public Class HelloModule
Inherits Nancy.NancyModule
Public Sub New()
Me.Get("/") = AddressOf Hello
End Sub
Public Function Hello(ByVal parameters as Object) As String
Return "Hello world"
End Function
End Class
If we use C# then the Application.cs file looks like this:
using System;
public class Application
{
static void Main(string[] args)
{
Nancy.Hosting.Self.NancyHost host;
host = new Nancy.Hosting.Self.NancyHost(new Uri("http://localhost:8080"));
host.Start();
Console.ReadLine();
}
}
And we create a second class “HelloModule” with the following content.
using System;
public class HelloModule: Nancy.NancyModule
{
public HelloModule ()
{
Get["/"] = hello;
}
public String hello(Object parameters)
{
return "Hello world";
}
}
Running your Nancy application
If you press run and you might get the following error:
Error CS0246: The type or namespace name `Uri' could not be found. Are you missing an assembly reference?
Click on “Project > Edit References”, then type “System” in the search field, select the reference and click “OK”. If you get the following error:
/usr/lib/mono/4.5/Microsoft.VisualBasic.targets: Error: Error executing task Vbc: Argument cannot be null. Parameter name: pathToTool
In case you get the above mentioned error, again, go to “Build\General” and under the section “Build Engine” uncheck the “Use MSBuild build engine …”
And now open a browser and go to: http://localhost:8080/
If the page does not load it maybe because the application already exited. This can be solved by clicking “Run on external console” under “Project > Options > Run > General”:
And now press run, everything should work and you should see some “Hello World” magic!
Posting some data…
If you are using Mono’s VB.net compiler (vbnc) you cannot use “extension methods”. Unfortunately lots of functionality in Nancy actually depends on that. You may run into this first when you are trying to “Bind” the posted data to your “Model” using “Nancy.ModelBinding”. The error you will get says:
Error VBNC30456: 'Bind' is not a member of 'HelloWorldApp.HelloModule'. (VBNC30456)
You can avoid using the “Bind” method by actually reading the values from the “Request.Form” dictionary using:
Model.Id = CType(Ctype(Request.Form("Id"),DynamicDictionaryValue).Value,Integer)
You can imagine it may become quite hard to build software when you cannot rely on the Nancy manual on their wiki nor the numerous Nancy examples on Github. If you use C#, then you are not facing these difficulties as the Mono C# compiler is much more advanced than the Mono VB.net compiler. For this reason I am looking at compiling the Nancy part in C# and the business logic in VB.net and running them in a single solution. Check out my next post on this topic!
Finally..
You will learn that the MonoDevelop environment works flawlessly for C#. You may be able to create a working application with it for VB.net, but that won’t be easy. It is not the missing code completion that makes it hard. Things like “extension methods” which Nancy uses, and are supported by the Mono runtime, are not supported by the Mono VB.net compiler (vbnc).
The Nancy framework will feel very familiar if you have experience with frameworks like Sinatra, Silex or Flask. Mono is great for programmers that prefer Linux and as long as you program in C# (and not VB.net) it does not limit your possibilities. If you are going to run Nancy code in a production environment, then you may want to read about running Nancy behind a Nginx webserver.
NB: If you like this article you may also want to look into running ASP.NET vNext on Linux as well explained by Graeme Christie.
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