dev topshelf, windows_service, csharp

Topshelf

In almost all projects I’ve worked there was always a need for scheduled background jobs. Windows Services are well-suited for the job but when it comes to deployment and debugging they fall short. This is where TopShelf comes to rescue!

TopShelf in action

With TopShelf all you need to do is create a Console Application as your Windows Service and initialize TopShelf in the Main method:

Topshelf

Configuring it is quite easy and straightforward. It also has a nice comprehensive documentation on its official site. You can define all the parameters like the account that will run the service, the recovery policy and start-up type.

What about scheduling

Scheduling is also a crucial feature in background services. TopShelf doesn’t help with that but that’s easy to fix with FluentScheduler.

Topshelf

FluentScheduler is yet another great library available at NuGet which makes scheduling a breeze. No need to fiddle with timers, it can be defined very easily.

And here is the sample code:

Resources

dev git

If you have multiple accounts for git providers (i.e multiple accounts on Github and/or Bitbucket) then you’d need to update your SSH configuration to be able to access all your repositories seamlessly. Of course you can use HTTPS but then you’d have to enter username and password every time.

If you don’t specify which key to use for each account SSH agent will try the default key if there is one (id_rsa) and will most likely fail if you didn’t grant access to that key in your git provider settings.

SSH Access Denied

To resolve the issue you need to create a config file under .ssh folder that looks like this:

SSH Config

If you are just using one account per provider you don’t need to create multiple keys, you can just use id_rsa for both accounts. But if you have multiple accounts for a provider you’d need a key for each account. In the example configuration above I used a new key for BitBucket anyway. After creating the config file and adding the keys to your accounts you can start cloning repositories from various sources.

Final step to accomplish this is to use the hostname you set in the config file when cloning the repository. For example when you copy the SSL clone URL it looks something like this: git@github.com:{account name}/{repository name}.git. So let’s say it’s a repository from the corporate account in my sample config file then I’d have to modify the URL as follows: git@github-corporate:{account name}/{repository name}.git so that the correct host name and RSA file can be used.

SSH Success

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devhobby lego, mindstorms, ev3

I had my eye on the new Lego Mindstorms set for a while. Finally I decided to order it from Amazon. It’s still a bit pricey but I think it’s worth it. I read nice review of EV3 here which also includes comparisons to the previous generation of the Mindstorms kit.

Lego Mindstorms EV3

Programming EV3: The Official Way

Programming the kit is very easy using Lego’s official graphical programming tool. You just have to drag and drop the components and fiddle with the parameters. Check out the following very basic application:

Lego Mindstorms EV3

It powers the motors connected to ports B and C. It keeps doing that in a loop as long as the value read from Infrared Sensor is larger than 20. If there is an object closer to 20 centimetres it breaks and ends the program.

Programming EV3: The .NET Way

The .NET API is an open-source project. I recommend watching the introductory video which shows the basics. It shows how to move the robot by sending direct commands to turn the motors and how to read values from the sensors. The following part the test application shows the event handlers for the direction buttons and setup code to connect to the brick.

Lego Mindstorms EV3

I also added a similar implementation of the NXT-G program above. It’s a while loop which breaks when the value from the IR sensor is lower than 10.

Lego Mindstorms EV3

And voila! Now my clever robot senses the object in front of it and avoids the collision by stopping!

You can find the source code for the test application on GitHub

Tips & Tricks

  • When I first implemented the NXT-G equivalent version the sensor value wasn’t updating properly. I checked the discussion forums in the CodePlex project page and found out that other people were having a similar issue. A workaround was adding the Thread.Sleep(10) line. After that I could read the updated sensor values without any problems. Although it doesn’t feel like the right solution it works fine as a temporary workaround.

  • During the testing and debugging I managed to crash the Lego brick a few times. First I feared I actually “bricked” the brick but luckily a reset resolved it. Resetting the brick is not obvious though, I had to check the manual for that. So in case you need to reset it you have to hold down Back, Center and Left buttons. Then release the Back button when the screen goes blank and release the other two when the screen says “Starting”.

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