Monthly Archives: April 2017

Software development

.NET Core Tools Telemetry

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Microsoft may be winning the hearts of developers with their open-sourcey behaviour, but their attitude towards privacy hasn’t changed at all. As if Windows 10 sending usage data to Microsoft wasn’t enough, the .NET Core toolchain does it too.

It’s called Telemetry, and the .NET Core documentation explains the extent of the data that is sent to Microsoft whenever you run a dotnet subcommand.

The problem with .NET Core’s telemetry is not so much the nature of the data that is collected, but the fact that it is done by default, and you have to opt out if you don’t want it. That’s exactly the opposite of how it should be, with many people citing problems of privacy, security, and corporate buy-in in Issue #3093 on GitHub.

The fact that the issue is still open after nearly a year shows that the quest to “improve your experience” (whatever that means) and “provide a great product” is a lot more important than your privacy.

To disable telemetry, you have to add an environment variable called DOTNET_CLI_TELEMETRY_OPTOUT and give it a value of 1. (There are other valid values, such as “true”.) If you follow the instructions and set it in cmd.exe (Windows) or export it in a Terminal window (Linux), as the official documentation suggests, that setting is only valid for the active command line window! Instead, follow the instructions below to set the environment variable permanently.

Opting Out Under Windows

Under Windows, go to Advanced System Settings (via Control Panel or directly from the Start menu) and add it to the environment variables from there.

Opting Out Under Linux

Under Linux, you can permanently set environment variables either by editing the script file for the shell you’re using (e.g. .bashrc for Bash), or else adding an entry in /etc/environment which will apply to all shells as well as non-shell windows:

echo "DOTNET_CLI_TELEMETRY_OPTOUT=1" | sudo tee -a /etc/environment

You will need to restart the system for this change to take effect.

Opting Out Under Mac

I don’t have a Mac, so all I can tell you is to get a decent OS. 😉

Seriously though, the same instructions for Linux should presumably work on a Mac.

Rants

On Overbookings

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“I never understood how overbooking is legal. (I know this wasn’t really an overbooking incident, and I know about the no-show excuse. But if you buy tickets for a cinema, or a theatre, or book a place in a restaurant, or whatever, they never tell you “Sorry, but we gave your place to someone else. Here’s a cookie.”)”
— Myself in a Facebook comment, 12th April 2017

The recent incident where a passenger was violently removed from a United flight to make room for United employees reopened an old argument about overbookings on flights. While this wasn’t in itself an overbooking incident (even though some airlines like to treat “overbooking” as an umbrella term encompassing even incidents like this), it reminded me of the intentional practice of overbooking, which is not just a desperate measure by abysmal airlines like Air Malta, but indeed a blight that plagues the greater majority of the airline industry.

Image credit: here

It is well-known that most airlines intentionally allow their flights to be overbooked due to statistics that state that on average, some 10-15% of booked seats result in no-shows. The excuse is that the seat left empty could instead be used to transport a passenger who does show up. This is obviously a slap in the face of the people who, conversely, do show up for their seat and are denied boarding because the flight was overbooked, and offered measly compensation for it.

If you make a booking at a restaurant, cinema, theatre, etc, they never tell you “Sorry, but we gave your place to someone else. Here’s a cookie.” You booked a place, and they are supposed to respect it. Of course, you might not show up, and that’s a risk on them.

But in the case of flights, you pay for them in advance. Whether you show up or not, you actually paid for that seat. It’s yours. How is it even legal to sell that same seat a second time to someone else? It’s like selling the same item at a store to two different people, have both pay for it, expect the losing party to actually ask for his money back (and keep it if they don’t), and let them just live with the disappointment.

I am really furious not only that airlines carry out this sleazy practice, but also that the authorities allow it to happen. Even worse, the compensation (at least here in Europe) is pathetic. It barely makes up for lost time at work, and has absolutely no consideration about stress and hassles that take place as a result, including the eventuality of having to cancel holiday plans, miss connecting flights, and run after airlines for compensation. As I had already noted in my article about when Air Malta left us stranded, not only is the compensation not enough disincentive to leave passengers at the airport, but it actually makes it worth the risk for the airlines.

I’m sorry, but you just cannot justify this sort of gross mistreatment of customers by quoting passenger statistics and airline profits.

Software development

Setting up .NET Core on Linux

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One of the biggest promises of .NET Core is the long-awaited promise of true cross-platform development. In this article, we’ll see how we can set up .NET Core on some flavours of Linux, and ensure that it works by running a simple console application.

Introduction

In general, if you want to run .NET Core on Linux, you should do the following before even starting development, to make sure it actually works:

  1. Install .NET Core itself.
  2. Create a simple .NET project.
  3. Build and run the application.

The steps to install .NET Core vary depending on the distribution you are using. Different distributions use different package managers (e.g. APT, RPM, YUM, DNF, etc) so you will often need to either add a .NET package source to your package manager’s configuration, or download binaries for .NET Core from Microsoft, before you can proceed to actually install .NET Core.

Microsoft’s Getting Started with .NET Core documentation lists a handful of supported Linux distributions, each with their own installation instructions. Unfortunately, this is not yet updated with the latest versions of several popular distributions. In fact, I have not been able to set up .NET Core in Ubuntu 17.04 (Zesty Zapus), Fedora 25, or CentOS 7. So in this article, we’ll focus on Ubuntu 16.10 (Yakkety Yak) and Linux Mint 18.1.

Unfortunately, these two are both Debian flavours, and both use the Ubuntu package server, so there is not much in the way of variety here.  In any case, let’s proceed with the setup.

Installing .NET Core on Linux Ubuntu 16.10 (Yakkety Yak)

First, we need to follow the installation instructions in the documentation in order to add the .NET package source to APT’s package source configuration:

sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/dotnet-release/ yakkety main" > /etc/apt/sources.list.d/dotnetdev.list'
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 417A0893
sudo apt-get update

Here’s what the output of most of this should look like:

With that done, we can install the .NET Core SDK:

sudo apt-get install dotnet-dev-1.0.1

Once the installation is complete, we can create and run a simple project. We can do this without writing any code ourselves, because the dotnet command provides means of generating project templates out of the box.

First, let’s create a directory for our application, and switch to it (note: the documentation provides an alternative way of doing this):

mkdir hello
cd hello

Then, we can create a simple “Hello World” console application in the current directory by running the following command:

dotnet new console

Then, with the following commands, we restore dependencies via NuGet, build the application, and run it:

dotnet restore
dotnet run

Here’s the output, so you can see that it actually worked:

Installing .NET Core on Linux Mint 18.1

The same documentation page with the instructions to install .NET Core on Ubuntu also covers Linux Mint 17. Unfortunately, this doesn’t work for Linux Mint 18. However, you’ll notice that Ubuntu 14.04 and Linux Mint 17 share the same setup instructions. And this Stack Overflow answer shows that Ubuntu 16.04 and Linux Mint 18 also use the same setup. Thus:

sudo sh -c 'echo "deb [arch=amd64] https://apt-mo.trafficmanager.net/repos/dotnet-release/ xenial main" > /etc/apt/sources.list.d/dotnetdev.list'

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 417A0893

sudo apt-get update

Then, like before, we install the .NET Core SDK:

sudo apt-get install dotnet-dev-1.0.1

And then, we can actually test this out:

mkdir hello
cd hello
dotnet new console
dotnet restore
dotnet run

We get our “Hello World”, so it works!

Conclusion

We’ve seen how to set up .NET Core on the Ubuntu and Mint distributions of Linux, which are very similar. Different distributions have different setup instructions, and it would be a real pain to cover all of them. The official documentation does provide installation instructions for a handful of popular distributions, but they are slow to update documentation, and do not at this time cover the latest versions.

At least, however, this should be enough to get an idea of what it takes to set things up and run a simple application on Linux using .NET Core.

Software development

Playing a WAV File Using SDL2

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Sound effects and music are fundamental in giving life to a game. In this article, we’re going to see how we can play a simple WAV file using just the native SDL2 Audio APIs. Unfortunately these APIs are very tricky to use, and the documentation is littered with incoherent examples and legacy function calls. For this reason, most people prefer to use the SDL_mixer extension library to handle sound and music.

The source code for this article is available at the Gigi Labs BitBucket repository. It includes a sample WAV file generated with Bfxr. You will need to copy the WAV file into the output directly (along with SDL2.dll) before running the program.

While error handling has been omitted in this article for conciseness, checking the output of each SDL2 function call and showing something in case of error (e.g. using SDL_ShowSimpleMessageBox()) will save you a lot of hair-ripping experiences.

In order to use audio in SDL2, the first thing we need to do is initialise the audio subsystem when we initialise SDL2 itself:

SDL_Init(SDL_INIT_AUDIO);

We can play simple sound effects in SDL2 by loading and playing a WAV file. We can load a WAV file by calling SDL_LoadWAV(), passing in arguments which it will populate with data read from the WAV file:

	// load WAV file

	SDL_AudioSpec wavSpec;
	Uint32 wavLength;
	Uint8 *wavBuffer;

	SDL_LoadWAV("Powerup5.wav", &wavSpec, &wavBuffer, &wavLength);

The next thing we need to do is get a handle on our audio device, which is a fancy way of saying speakers (or headphones, or whatever).

	// open audio device

	SDL_AudioDeviceID deviceId = SDL_OpenAudioDevice(NULL, 0, &wavSpec, NULL, 0);

You’ll notice we have a bunch of arguments, and for most of them we aren’t really caring about the details and passing in NULL or 0 to get reasonable defaults. Below is a summary of what each argument does; feel free to skip it if you just want to get something up and running quickly.

  • The first argument is the name of the audio device you want to open. While you might have several, passing in NULL will give you a reasonable default audio device. You can, however, use this to explicitly name a device you want to use – see SDL_OpenAudioDevice() documentation for more detail.
  • The second argument is relevant to recording devices, and we don’t care about it for playback.
  • The third argument represents the desired audio output format. We already got this information when we read the WAV file.
  • If provided, the fourth argument will be populated with the actual output format of the audio device. In our case, we don’t care, and can pass NULL.
  • The fifth argument is for advanced scenarios and we don’t need it either.

Now that we have a handle on the audio device, we can actually play something:

	// play audio

	int success = SDL_QueueAudio(deviceId, wavBuffer, wavLength);
	SDL_PauseAudioDevice(deviceId, 0);

SDL_QueueAudio is a handy function available since SDL 2.0.4 (at the time of writing this article, the current stable version is 2.0.5) that lets you send WAV (audio) data to the audio device without having to register callback functions (which is what you’d otherwise have to do).

SDL_PauseAudioDevice() is used to pause/unpause audio playback on the audio device (depending on the value of the second parameter). By passing 0 as the second parameter, we are enabling playback (i.e. unpausing the audio device), and this allows the sound to be played.

Let’s add a small delay so that we can hear the sound before the application exits:

	// keep application running long enough to hear the sound

	SDL_Delay(3000);

Finally, let’s remember to clean up after ourselves before exiting the application:

	// clean up

	SDL_CloseAudioDevice(deviceId);
	SDL_FreeWAV(wavBuffer);
	SDL_Quit();

	return 0;

We can now run the application, and should hear the sound play if everything is set up correctly. If not, then:

  • Remember to have both SDL2.dll (if running under Windows) and the WAV file in the output directory.
  • Make sure the path to the WAV file is set correctly. If running under Visual Studio, you may also need to change the Working Directory project setting. See the last part of “Setting up SDL2 with Visual Studio 2015” for instructions on how to do this.
  • Add error handling logic, as suggested at the beginning of this article.
Software development

Multi-Targeting .NET Standard Class Libraries

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The .NET family has grown quite a bit, and to be honest, it’s a bit of a confusing mess. As I already explained in “Migrating Dandago.Finance to .NET Core“, there are now several different types of class library you can choose from (including different kinds of portable class libraries), different ideas of cross-platform (.NET Core vs Universal Windows Platform), different frameworks, and .NET Standard.

Let’s consider the following image, which shows three different .NET-based frameworks in relation to .NET Standard:

Image credit: .NET Core, .NET Framework, Xamarin – The “WHAT and WHEN to use it”

Your applications will typically be built for one of the frameworks on top (e.g. .NET Framework). But when you create a class library, you can choose to have it target a specific framework, or .NET Standard. Just as a quick recap from “Migrating Dandago.Finance to .NET Core“, targeting a particular framework (e.g. .NET Core) will not let you use the class library on others (e.g. .NET Framework), but targeting .NET Standard keeps it compatible with all of them.

This means that class libraries that target .NET Standard have maximum compatibility, but there’s a cost: not all APIs are available for .NET Standard, and targeting .NET Standard is only compatible with certain recent versions of those frameworks. If you take a look at the compatibility chart, you’ll notice for instance that .NET Standard 1.3  supports .NET Framework 4.6 and onwards.

For the most part, this is okay. But sometimes, you may want to combine .NET Standard compatibility with specific features in a particular framework, or perhaps target .NET Standard but still support older versions of a framework because you have some legacy code you can’t upgrade yet.

Multi-Targeting

When you create a new .NET Standard Class Library, its .csproj file will look something like this:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard1.4</TargetFramework>
  </PropertyGroup>

</Project>

It is now actually possible to target multiple frameworks, by changing the <TargetFramework> element to <TargetFrameworks> (just add an ‘s’) and putting in different target framework monikers separated by semicolons. For instance, the .csproj file for my .NET Settings Framework looks like this:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>netstandard1.2;net452</TargetFrameworks>
    <!-- ... -->
  </PropertyGroup>

  <ItemGroup Condition="'$(TargetFramework)' == 'net452'">
    <Reference Include="System.Configuration" />
  </ItemGroup>

  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.2'">
    <PackageReference Include="System.ComponentModel.TypeConverter" Version="4.3.0" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Configuration" Version="1.1.1" />
    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="1.1.1" />
  </ItemGroup>

</Project>

In this project, I’m targeting .NET Standard to provide as much compatibility as possible, but I’m also using framework-specific assets from the .NET Framework (namely System.Configuration, which is used to work with App.config/Web.config files). Thus, I am targeting both .NET Standard 1.2+ and .NET 4.5.2+. This has the effect of creating separate builds for each framework.

I have dependencies in there that are applicable for both targets (the section at the end with no conditions), but I also have specific dependencies needed for each framework. For instance, the functionality that needs System.Configuration will only be available for the build that targets the full .NET Framework, and will not be usable in the .NET Standard build. Such functionality will have to be written within preprocessor directives to prevent them from breaking the other builds:

#if NET452

using System.Configuration;

// ...

#endif

Unfortunately, as of now, you have to edit the .csproj by hand if you want to do multi-targeting, because the Visual Studio tooling hasn’t quite caught up with it yet. In fact, the project settings will only allow you to target a specific version of .NET Standard from a dropdown:

And after you’ve edited the .csproj by hand, it won’t let you change it from the GUI:

Summary

  • Targeting .NET Core lets you go cross platform, but you can’t use that functionality with other frameworks.
  • Targeting .NET Standard is compatible with any framework that supports that version of .NET Standard.
  • You can multi-target a .NET Standard library to include framework-specific functionality (guarded with preprocessor directives) while keeping the rest of the library compatible with all the relevant frameworks.