02 Mar 2015

Events you should attend

Clipboard01What’s New Roadshow

Starting next week the What’s New Roadshow (or as it is officially called, Dev Day) will be happening in Johannesburg (already sold out), Durban & Cape Town. This should be a great fun event, where we will be covering some interesting concepts in the land of .NET which don’t get enough time, for example Machine Learning. We will also be looking forward with VS 2015 and C# 6 coverage! I will be tackling the C# 6 content (which has already wowed the internal teams) & also covering DevOps. The events are free but you need to register so catering & seating can be taken care of!

Developer User Group

Also next week, is the monthly developer user group meeting, and it looks fantastic! Each month, on the second Tuesday of the month, the DevUG meets from 16h30 to 18h00 to learn & share. Next week we will have topics ranging from Flying Quadcopters with Node & learning Go!

Any events you attend or want me to share? Send them over in the comments!

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27 Feb 2015

Xbox Live Gold? Don't forget this trick to get free games!

Clipboard01Each month Xbox gifts their Xbox Live Gold members a number of free games. Something remember is that you get ALL the games, regardless of the console you own! That means, if you only have a Xbox 360 you still get the Xbox One game; so when you do get a Xbox One console you will have a LOT of free games already. To get your game, you need to go to the marketplace on the  Xbox website to “purchase” your free game.

That’s it! What is your favourite Xbox game? Let us know in the comments!

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06 Feb 2015

I dropped a large binary object in Git ... now what?

Clipboard01or how do I remove a file from Git, including the history. This came out of a discussion with some ALM Rangers (in fact the title was from Willy-Peter himself!) and I thought it is too good not to share. In addition I’ve added some other information I learnt since then!

Before you start

Make a copy of your git repo before you start! We are going to mess with your repo, so if you have a backup and something goes wrong you can just rollback.

Revert

If you have ever made a mistake on a computer, you know it the moment you finger lifts off the enter key. So you may just want to undo that last commit quickly and use the revert command in git, which appears to remove it, but the problem is that remains in the history. So this means that everyone needs to get it when the clone or pull the repo.

Amend

If the very last commit added the offending file and you NOT pushed your repo yet there is a simple process to solve it. First delete the file. Then run another commit with the --a and --amend switches. 

  • --a  tells git to automatically stage all modified & delete files.
  • --amend tells git to rewrite the last commit.
  • if the only thing was that file, then you may need to add a --allow-empty switch to tell git to accept a commit with nothing in it.

For example, if I want to remove the password.txt file.

del password.txt

git commit --a --amend

Rebase

What if it isn’t the last commit, but a few back. Once again if you have not pushed your repo an option would be to rewrite history (you may want to look at that link, it goes in DEEP detail on what rewriting history means). Step one is to kick off a rebase and in the editor go to the commit with the issue and change it from a pick to an edit, for example:

git rebase -i origin/master 

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(in the picture above, I am going to remove the file added in commit 47f73e6)

You will then be dropped back to the command prompt, and you can step through the commits you set to edit. You can make the changes (either edit the file or delete it) and then use the same amend as before. Once you have finished that you step the rebase forward by doing rebase --continue.

For example:

del password.txt

git commit --a --amend

git rebase --continue

Filter-Branch

What if you have pushed? Or perhaps you need something more? Git includes a solution for this, called filter-branch which was totally unknown to me before this discussion. Filter-branch is not only useful to remove files but you could also change the details of a number of commits (for example: updating your email associated with your commits).

Lets get rid of the file, for example password.txt

git filter-branch --tree-filter "rm -f password.txt" HEAD

Note – on Windows you will use double quotes (“) like above, but on Linux it would be a single quote (‘). Once done you need to push to git, but you will need to use --force and --all switches to do it.

git push --force --all

Your next issue is that all your team members still have the file (if they already have pulled), so they need to clean up to. The way they do this is to run rebase but using the onto switch this time. For example:

git rebase --onto origin/master master

Those members who haven’t pulled since that file got into the repo, can pull as normal and do not need to worry about this.

BFG

There is also a stand alone tool called BFG Repo Cleaner. There is a nice set of documentation for it and it is blindingly fast! One nice thing is you can say remove all files above a certain size or or x number of the largest files.

GC

One thing to do once you have done all of this, is run a garbage collection by using the gc command, which may return disk space from orphaned files. To do this run:

git gc – --auto

That’s it! Have you ever messed up a file (I have, I committed my Azure password once in a file!)? Share what happened and how you fixed it!

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03 Feb 2015

Why I am proud of my planet sized unit test

Clipboard01I am having a lot of fun with a new project, one where the customer said we had to do unit tests (how rare is that Smile). It is still VERY early days in the project so by the end maybe I will realise this is wrong but for now, but right I am pretty proud of one specific test. It is 50 lines of long (C# + XUnit) and 18 of those lines are asserts. If the normal practise of unit tests produces asteroids, then this is a planet sized unit test. When I wrote it, I immediately felt the weight of hundreds of purists telling me it is wrong or that it has too much complexity & will hurt me.

Is this the norm for the project?

No – it totally will not be. Most unit tests will be sub 10 lines and have one or two asserts. I believe planet sized unit tests will account for 5% of the tests at the end of the day.

You’re doing unit tests wrong!

No – there is some advice I am choosing to ignore, but really it is just advice. Why is that advice there in the first place? It is there because people with far more experience and knowledge have learnt that the larger a unit test becomes (for this just assume size = complexity), the more brittle it becomes and the more time will be spent trying to understand and maintain it. In short the value vs. risk equation breaks down (i.e. high value & low risk is awesome but low value & high risk is a bad idea). So here is the rub, for 5% of the tests we have a very high risk but they exercise the code in ways that provide a massive amount of value.

So what does it do?

I think calling this a unit test is wrong, I feel that even though it uses unit test tools & is part of the unit test project it really isn’t a unit test – it is more of a process test. We are testing how the user would run through a specific process from end to end. These process tests exercise the interactions between various pieces which a single unit test might not. I had thought to call these integration tests, but we aren’t integrating to any external systems – everything is still mocked out and injected in. Another way to look at this, and in fact this is how we structured it, it is multiple unit tests (each with a arrange, act, assert pattern in them) chained together.

I have used these in previous projects and the value of them is stupidly massive. The often find issues long before a unit test will because so much is coupled together, you could say that the increase in complexity actually increases their value.

Why so many asserts?

How I figure out who to assert is simple, I follow the advice: Assert all your assumptions. For unit tests since they are simple, the assumptions can be simple. For a process test, since it is complex you should have more assumptions during each part of it. 

This is what I am doing, have you ever tried a planet size test or a process test? What did you find in it?

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30 Jan 2015

My toughest bug of 2014!

The first sign of a problem was when the app crashed while I was testing a new feature I put in. The error in VS indicated a XAML issue which was odd, since I wasn’t working with XAML at that point. I restarted the app and no error occurred. “Meh, what ever” was my response. The second sign of a problem was when another developer on the team, a week later told me about the issue. My response – shrugged it off and told him to restart. The third sign was when the testers logged a bug about it – finally someone was making this a real issue. You may hear that a developer & tester are better than two developers – this is a great example of why: two different perspectives of what really is an issue does really help.

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The app we were building was a Windows Store App for Windows 8.1 using XAML & C#. It was being built using the Universal App Framework. It was also big for an app with over 40 screens! The XAML for our custom controls & styles is over 2 000 lines of XAML!  The bug could be anywhere, but it had four traits:

  1. The error which told us it was a XAML issue & related to a ContentPresenter: Failed to assign to property 'Windows.UI.Xaml.Controls.ContentPresenter.Content'
  2. It only happens when we navigate between pages.
  3. It was not limited to any one page. It could happen on any page.
  4. It is intermittent – very intermittent. Make you scream levels of intermittent. I’ll introduce you to Heather later, but she told us that it was 1 in 40 times on average it would happen!

So how did we fix this? This is a story of the dumb things I did followed by the smart thing I did.

Starting to understand the problem

Step one, we know it is XAML & it is on every page – so what is common on all pages? First is our styles.xaml where we store all the common colours & styles for the app. Second is a custom control we built, called PageLayout, which gives us a common layout and pieces of functionality (basically it is similar to the Frame control). If you are interested the XAML for that control is here. The key thing which suggested the XAML control was the cause was it has FOUR content presenters on it and the error suggested a content presenter was at fault. I reviewed the XAML & so did another dev – no problems found. 

One thing happened, when we tweaked the XAML for PageLayout the line numbers in the error changed. So we knew the problem was there – but what was it?!

Windows Debugging

We were running the app outside of Visual Studio one day and it crashed. You know what is awesome in Windows? It will grab a memory dump for scenarios like this – so we got a memory dump of the error! This is awesome because we can use Visual Studio to work with those and there is a fantastic blog post on exactly how to work with it. You know what two hours of doing that told me… nothing. Come on, what is all that text below if we had the answer now. Keep up reader. All I could get was the following error message: Unhandled exception at 0x7582B152 (combase.dll) in triagedump.dmp: 0xC000027B: An application-internal exception has occurred (parameters: 0x055C31F8, 0x00000004).

I also got stuck since I didn’t have the Debugging Tools for Windows and over a gig of download wasn’t going to happen at work, but that may have been a blessing in disguise. Through this though, I did find this great Wintellect Now video on how to debug on a OS level.

The birth of Heather

So after spending hours of repeating the process of making a small change and then clicking through various screens over & over again (and thus making sure carpel tunnel syndrome was coming) – I wondered, can’t I automate the clicking. Actually I don’t need clicks, I just need navigations to a different page. So I created a new universal app, with a single page in it. I then copied PageLayout and everything it needed over – totalling 300 lines of XAML! I added a single button which automatically navigates to the mainpage over and over again. You can see this code base here.

This app is called Heather Speed Crash! and boy did it deliver, it could crash every time! It was still intermittent but it meant I could get it happen in < 60s with one click rather than > 20 clicks & 5 minutes. This helped a lot in getting work done. It also meant that the code base was less than 500 lines of code + XAML compared to the actual app of thousands of lines of code.

Now to iterate over Heather and clean it down and still get the errors which led to this version, which got us down to less than half the code + XAML & it also showed the exact issue was in the PageLayout. Not something which PageLayout used. This is one of the biggest learning's from this, intermittent issues aren’t some pain to resolve, the trick is just to make the scenario happen faster.

Two lines of XAML

Somewhere between starting to understand the problem & diving into Windows Debugging, I realised that I was struggling with the problem and I decided to post the issue to StackOverflow and then, a few days later, to MSDN forums. This is always a valuable exercise for me as it forces me to put down in a systematic way and often just the act of collecting, ordering and writing down the information shows me what the problem is. This time, writing didn’t help and after a few days I had no progress with it. On the MSDN forums, it was suggested that I try identify which of the four content presenters was the problem. Now that I had Heather to help, I could do this. The process I went through was:

  • Comment all four ContentPresenters out – run – it works! This is great because we know it is one for four lines of XAML!
  • Comment each one in individually and test. Of the four, only two crashed! So we are down to two lines of XAML!

These two content presenters were not used on ever page, so their binding to content was set to null by default. This was the only difference between these two & the other two. So I gave each a default piece of content and the problem stopped. Oddly, if I gave just one a default piece of content and left the other presenter null, it would also be resolved.

The issue turned out to be a layout bug somewhere deep in XAML which is triggered only when two content presenters both exist on a page with null content. When XAML tries to work out the sizes of the controls, having two nulled content presenters causes a crash.

The work around to resolve this was to have both content presenters visibility set to collapsed by default & only make them visible if they have content.

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15 Sep 2014

Rules for better email

tl;dr: Some one was dumb & used a good idea to excuse being lazy. It gave me an idea. I created a micro site to share simple rules for better email!

Sentenc.es is a novel idea to have more meaningful email communication by applying a discipline to how you respond. The suggestion it offers, is to limit your responses to  certain number of sentences or less. They have pages for two, three, four and five sentence lengths.

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Picture from Intersection Consulting

I am all for ideas to improve email – I GET A LOT OF IT, sometimes it feels like I am drowning in it. I use unroll.me and a million filters in my email client to try and cope. I also love the idea senten.ce offers of being disciplined to responding, but there is a problem.

The problem is people (when isn’t it). This was highlighted for me recently when I questioned someone on why their emails were short, rude & insulting. Their answer “You misunderstood my tone”. When pushed further it turns out the reason he couldn’t craft his emails to get the tone right, was because he blindly followed the three sentences rule.

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Picture from darkuncle

The mistake made here, which is made not only with this idea but with many, is to be too focused on being disciplined that you lose sight of the bigger picture. Another place I’ve seen this is with scrum, where they “do it by the book” even when they are hurting because of it. Agile is helping with scrum, but what can we do for the “senten.ce sheep”?

The solution!

I decided to make a micro site called Rules for better mail, which like senten.ce, has what I think are better rules. Share it, put it at the bottom of your emails, ignore it, contribute to it or what ever you feel like, I am not your mom – you don’t need to listen to me.

01 Jul 2014

Improve the embedded browser in Visual Studio

Visual Studio has an embedded browser, but it uses the IE 7 render path?! Really, that is pretty messed up.

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and worse it can cause the Internet to break

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Thankfully, you can fix this yourself with a quick registry addition. Note: Fiddling with the registry can break your device, so be careful and this carries the usual “this works on my machine” and it is your own risk for doing this.

The key you need to care about is:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION

Note: the Wow6432Node bit is needed since Visual Studio is a 32bit process. In there, add a new registry key of DWORD type named: devenv.exe

I set the value to (HEX) 2af9 – since I have IE 11 on my Windows 8.1 machine, but you can pick from the list of options to best suit your needs and now it just works!

No issues on GitHub

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A much better looking user agent.

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15 May 2014

The Rangers Treasure Map Updating System

In the next release of the ALM Rangers Treasure Map one of the new features is a way to update content remotely in the app. The mechanism chosen for this is intentionally simplistic as it allows us to run this with minimal infrastructure as well as focus on the app development and not building server side code.

How it works?

Presentation2The system is very simple, but first let’s look at how content is handled internally. We store all content in XML and we have a folder full of images (we will call this collectively Assets). One of the changes needed in this release was code that copies the assets from the install location to the sandbox location – the reason for this is because we cannot write to the install location.

The update mechanism really just connects to web server and downloads a zip file, extracts it and overwrites the XML and images. We do have some extra logic internally which ensures that we do not waste your bandwidth – this is done by checking the if modified since in our request and we can see if we have new content available.

Setting up Azure

Unfortunately not every server supports the if modified since headers, but thankfully Azure Websites do support it. Using Azure websites allow us many ways to push to it which makes the work flow for updating content very easy. It is also very easy to set up the site:

Login to the management portal: http://azure.microsoft.com/en-us/account/

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In the management portal – go to websites

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Click NEW (lower left hand corner). Website should be pre-selected, if not, select it. Click quick create and specify a URL and hosting plan. Click create website.

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Next click on the website which was created and click Reset your deployment credentials.

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Specify a username and password and click OK.

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And that is it!

Crafting the content

So how do we build the ZIP file which needs to be uploaded? Since we have two different sets of assets; first the art (images, photos, logos etc…) and second the data (as XML). These are stored in two different locations for the app: DataProviders, which contains the data, and Assets, which contains the images. So we setup the two folders and put the new items and data to be replaced in the right folders:

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We then compress those folders into a normal ZIP file and upload it. It is that simple.

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