Switching program from .Net 4.0 to 4.5

If, like me, you switched your .Net program from 4.0 to 4.5, you might have encountered a bunch of problems.

What worked for me is the following.

First, modify your projects to use .Net 4.5. Make sure it builds (even if you might get a bunch of errors). Save and commit.

Next, run the following command in the VS package manager console:

This should reinstall your Nuget packages without touching their dependencies.

If you still get MSB3277 errors (“Found conflicts between different versions of the same dependent assembly that could not be resolved”), follow these steps:

  • In Visual Studio, open tools > options > projects and solutions > build and run > select “detailed” for the two msbuild output options.
  • Build your project
  • In the “output” window, search for MSB3277. Go up a little bit, and look for “A conflict exists between…”. It will tell you which assembly is conflicted.

Myself, it was the System assembly… weird.

The both most simple, and most annoying solution, is to remove all references and Nuget packages, then add them back.

Using NUnit for a .Net 4 project in a Jenkins installation

I have migrated my MBUnit tests to NUnit, considering MBUnit has been “on hiatus” for about a year now. NUnit is not much more agile, but at least there is a semblance of life on their Github account.

The switch has been surprisingly easy: change the namespace, change TestRow with Test, and change Row with TestCase. Easy!

Run unit tests in your continuous integration platform

In order to integrate the tests in our continuous integration platform, while minimizing build time, I have split the setup package build and the unit tests run. So I have a job that runs at each commit, that builds the project and generates the setup packages; and another job running at midnight, that only builds the project and runs unit tests.

Apparently, using the automatic package restore from Visual Studio is now obsolete with the latest Nuget versions. So I followed the instructions and migrated to Nuget package restore. Remember to download nuget.exe from nuget.org, add it to the CI server’s PATH, and restart Jenkins.

Add the NUnit Nuget packages to the test projects, and remember to add the NUnit Runner Nuget package to the solution! It will be much easier to run the unit tests this way (no need to install NUnit on the CI server).

I’m using PSAke for my build process (awesome tool!), so now my script looks like this:

And now my Jenkins jobs consist of a simple batch line:

I have sumbled on a System.BadImageFormatException while running tests in Jenkins using nunit-console, or trying to add the assemblies to the NUnit GUI runner. Here are a few things to remember:

Do not use AnyCPU

Your test assemblies, assemblies linked by your tests, and really your whole project, should be built in 32-bits mode, so that they can be run by the 32-bits test runner. Personnaly, I created a “NUnit” solution configuration just for this. It allows me to select which assemblies are built in which case: no need to build tests in the general build, and no need to build stuff like bootstrapper exes in the test build.

Check your build paths

If you create a new configuration like I did, remember to change the build path! My main project builds in the \build\app folder, and my tests are located in \build\tests. I spent a few minutes wondering why the platform change did nothing, before finding out that my x86 test assemblies were in bin\x86\NUnit (the default value).

Check the framework version

Select the proper .Net framework with the /framework:net-4.0 switch. NUnit should be able to find out automagically, but sometimes it doesn’t.

WPF/SOAP configuration for third-party webservice with empty security headers

I am writing a program that accesses a SOAP webservice written by a third-party provider.

I need to provide a user and login in the SOAP headers, which is kind of easy, in theory:

  • add the webservice reference to Visual Studio
  • instantiate a new “XXXXClient” generated class
  • set xxx.ClientCredentials.UserName.UserName and xxx.ClientCredentials.UserName.Password

Easy as pie. Except when it’s not. You see, the provider’s webservice is written using php, it does not behave nicely with .Net. When you send the request, you can see on Fiddler that the query is sent and gets a response, but .Net does not like this response, and throws exceptions around.

First problem: it throws a MesssageSecurityException because of empty security headers in the response (see here). I first thought that I had the same problem, so I spent the day resolving the issue following this blog post, but it turns out it’s much more simple. To fix this, you must set the enableUnsecuredResponse in the binding’s security node to true. And in order to do that, your binding must be a customBinding. If you have a complicated binding, good luck switching.

Second problem: the mime type for the request and the response are different (“text/xml” vs “application/soap+xml”). To fix this one, you have to write your own custom text encoder (download the WCF examples at the top), and to do that… you have to create something like a thousand classes with a hundred lines each. Just for a simple mime type mismatch! Do not forget to also copy, from the downloadable examples, the BindingElement, BindingSection, ConfigurationStrings, and MessageVersionConverter !

So, for such a simple task, as is too often the case with Microsoft, I need to rewrite (or copy, here) a whole bunch of stuff, just to modify some pretty mundane and common behavior, which should be configurable in the first place. It shows how extensible WCF is, and how bloated the extending is.

Anyway, here is a working app.config. For the code of the custom text message encoding class, as I said, just copy the MS examples (and don’t forget to rename the types in the bindingElementExtensions).


Debug integrated WPF WebBrowser scripts using Visual Studio

Copied and modified from another blog for future reference.

Note that in order to debug the Javascript inside a WebBrowser control, you don’t need the source code of the application (neat!).

  1. Open Internet Explorer, go to Settings, tab Advanced, and, in the “Navigation” section:
    • Uncheck “disable script debugging” (both IE and Other)
    • Uncheck “Display friendly HTTP messages”
    • Check “Display a notification about every script error”
  2. Open an instance of Visual Studio. Open the Tools menu, Attach to Process, and on the “Attach to” line, click “Select…”, and only check “Script”.
  3. Run the program including the WPF BrowserControl
  4. Attach the Visual Studio instance to its process.

Now, open the “Solution explorer” tab/toolbox. You will see every Javascript file loaded by the WPF WebBrowser control, and you can add breakpoints where you want.

Tested with IE 11 and Visual Studio 2010.

Creating a C++/CLI wrapper around a C library

So, following my previous post, I have decided that I might try C++/CLI after all, since the SWIG way goes nowhere except “down in flames”, and I really need to implement it.

Turns out that creating a C++/CLI wrapper around a fairly well-made C library is not that hard.

Considering the following .h file from the C library (which are the methods and structures to interface):

Add the .h and .c files to a new C++ CLR DLL project, then add a new cpp file, in which we will replicate all the C structures as classes.
We have to name our classes differently than the C structures, otherwise there will be conflicts, both with the compiler, and in our heads.

The annoying thing when like me, you know pretty much nothing about C/C++, is that you never know where to specify pointers and stuff, and it’s mostly trial and error (it says it can’t build, let’s add a *… nope, a & ? Yes, that seems to work).

A few things to note:

  • Provide internal ToNative() methods on the structure wrappers to ease up marshalling from managed objects to native structures.
  • Also provide internal constructors taking a native structure as parameter, to ease up marshalling from native to managed.
  • The “^%” syntax (for the “images” parameter of the “Pack” method) builds to a “ref” in the .Net method signature. Otherwise the calling C# can’t get the values back.

As you can see, it’s not that difficult after all. I guess for an experienced C/C++ developer it would be even more simple.

Using SWIG to create a .Net wrapper around a C library

A consultant has written a C library to neatly pack images on a space. They have integrated it in their Ruby On Rails / Node.js online app through the power of extending Ruby. I’m quite jealous, because it’s not quite as easy to do in .Net. Especially when, like me, you know absolutely nothing about C/C++.

Two options are available to me:

  • Create a C++/CLI project, that will generate a .Net DLL
  • Use SWIG to generate a .Net wrapper around the C code.

Now, since I can’t change much the C code (it must be built on Mac through Ruby), I thought that I couldn’t easily switch it to CLI (I was wrong ; see the next post).

So I tried using SWIG. And it’s a pain to use. Let me walk you through creating a wrapper around a non-trivial C library.

Generating basic wrapper methods is pretty easy: it’s a matter of creating a .i file with a few lines of code:

Run SWIG on this file to generate a few C# files and a C wrapper class:

Then, you create an empty C/C++ library project with Visual Studio, include all the necessary files, and generate it. It builds a DLL, and you can include both the C# files and the DLL in your .Net project to use. Very nice, very simple.

A problem arises when you have a C method taking an array as argument: SWIG generates a C# signature taking a single instance as argument:

You can tell SWIG to create an “intermediate” array type by adding this to your .i file:

This creates an “image_t_array” class, with methods for setting and getting items, old-school-style. There is also a method to cast it as “image_t”, with pointers handling to go back and forth in the array.

Now, creating an array class, and cast as instance to pass it as parameter is not very intuitive, and I’m trying to create a usable wrapper. I want to pass an actual, managed array to my method. Is that so hard?

The SWIG documentation has a whole part about passing managed arrays to non-managed code. The problem is that (once again), the documentation is incomplete. It shows an example for a managed arrays of ints… but not an array of structs. Apparently it doesn’t work the same way, because SWIG complains about a missing typemap when using this:

Actually, a totally undocumented feature needs to be called just above this line:

Thanks to a nice fellow on StackOverflow for reading the SWIG sources… Googling for “CSHARP_ARRAYS” yeilds exactly zero result in the documentation, but only a few relevant results on forums and mailing lists. Why is it not documented, while it’s obviously necessary? If it’s not the right way, which is? Why not documenting the warning message that appears when you don’t use it?

So anyway, now my C# method takes a managed array as argument, which makes this library so much more easy to use. It throws a memory access exception when running the “pack” method, though (System.AccessViolationException).

Thankfully I have both the source files, and the pdb file for the unmanaged dll. I just have to copy the pdb to the target directory (using my test program post-build events), and once I activate unmanaged code debugging (managed project properties / debug  /activate unmanaged code debugging), I can step through the library, using the actual C code! Awesome.

At the actual point that an error occurs, I can see that the library tries to access an image in the array that is not defined. Weird. By adding a few breakpoints in the C library (I can’t imagine how I would have debugged that without the source code…), I quickly notice that my “*images” (in the pack) have very weird values, and that they do not correspond to the sent values at all.

Since passing values as arrays might do weird things with pointers, I decide to switch back to using the “image_t_array” class… and sure enough, now the values are correctly passed. I still have memory access problems, though, but that seems to be on the C side… but it runs nicely when a C++ program calls it, so I still have some digging to do.

At this point, debugging the wrapper becomes very complicated with all the layers involved, so I decided to try the C++/CLI way which, as you may see in my next post, is not that hard after all.

Use git with your SVN repository

You are just a few simple commands away to start using all the local power of git (local commit and rewind, stash…) over an existing SVN repository.

I say local power, because obviously, SVN being not as powerful as git, you’re still limited in what you can do without breaking everything when you try to commit.

A simple and effective guide can be found here : http://svnrating.com/svn-to-git-migration/

Note that on large SVN repository, the first checkout/clone can take hours, or even days. On our 2400-commits-large, several-Gb repository, the first clone has taken a few days, but it was making my (bi-Xeon + 16Gb RAM…) computer hang a few seconds or minutes every 15 minutes or so. Maybe you’ll have better luck.

But once it’s done… it’s really awesome.

Linq2SQL – Row Not Found Or Changed

Working on a .Net 3.5 client app, I am stuck using the lesser evil of Linq2SQL (compared to the awefulness that is EntityFramework 1).

Updating data on a column results in a ChangeConflictException : “Row not found or changed”. The usual culprit of the DBML differing even slightly from the actual DB model was not to blame, and the concurrency was not either, since the processing took a few milliseconds at worst, on a local DB.

It actually was a trigger updating the “updated_at” column. In the DBML editor, setting the column to “check update : never”  and “automatic synchronization : always” solved the problem.

Listen to your users

Why would I want to?

Why are we writing software ? Because we need, or we like, to solve problems.

I you write software for people to use (as opposed to embedded software, for instance), these problems will only be solved if these people actually succeed in using this software. This is, both surprisingly and annoyingly, incredibly difficult.

Your users are not dumb. They are not as well-trained as you are in using computers. They often will be far superior to you in their field of choice. Don’t underestimate them.

And even if you do underestimate them, or even if your users were actually not-that-smart, so what? Aren’t you writing software for them anyway? You are not your user.

How do I do that?

I urge you to do user testing. It will blow your mind, and might make you rethink your whole software. It doesn’t have to be huge, you just need to put people in front of your software, and watch them use it.

You can begin by asking co-workers that are not as familiar as you are with the product : a secretary, an accountant, a salesperson… If you’re in a building with other companies, you might ask people there. Better yet, if you can, ask real users (or prospective users) to come to your office.

Get in a room with them, get them on a laptop with a mic (most do, these days), install a capture software like BB Flashback Express, run it, then run your software or open your website.

Then, just ask the users to do common tasks. Insert this, edit that. Don’t help them. You might find plenty of help everywhere on how to conduct user testing.

How will it help me?

Listen to their remarks. Probe them for more informations. Don’t necessarily do what they suggest, but think about what problem they encounter, what problem they want to solve with their suggestions, and how you would solve it optimally.

Some examples of recent user comments that have had a tremendous impact on our recent designs :

I think I understand how to resize this block, but why does it display a “hand” cursor instead of an arrow ?

This allowed us to realize that our block resizing was even more awful than we thought, and we redesigned them completely. The blocks had arrows on the corners that allowed the users to resize, and on mouse-over the cursor changed to the “link click” cursor. The common pattern is that the cursor must change to a “double arrow” to resize. We were so used to this anti-pattern that we didn’t even notice it anymore. Now users finally understand how to move and resize blocks !

I think the previous version was more simple to use. I liked the toolbar.

This comment made us realize that our “clever” new design was in fact very confusing. The new design uses contextual panels and buttons in various places to do various actions, it’s kind of pretty, and has a lot of attention to details. The old one was using a single toolbar for all actions, was awfully ugly, with widely inconsistent icons that changed places depending on what you clicked. But users always knew that the actions were there. Now they’re lost, because the action to do X is on the left, Y is on the bottom, and Z is displayed in a contextual panel. It’s only this comment that made me realize why I was uncomfortable when watching users search for some actions: they are actually lost. We might have to rethink our whole design to switch to toolbar-based.

That’s it?

Of course not. It’s very easy to do enhancements with just that, but it won’t allow you to build the best software out there. But there is some help available everywhere.

I personnally started with Steve Krug’s “Don’t make me think” and “Rocket Surgery Made Easy” : they are very concise and to the point. I’d consider them mandatory readings.

There are many great usability blogs out there: try out (in no particular order) Smashing Magazine, UX Magazine, UXMatters, Boxes And Arrows, The UX Booth, UX Movement, Usability Counts, Wireframes Magazine… the list goes on.

I am sure this small start will help you a great deal.

Abstract away constructor logic

I need to create an administration interface in MVC, over an old and seriously crappy DB. The fields and tables have no consistency whatsoever, but that’s easily solved through renaming things with Entity Framework. But now, I need to do 5 administration interfaces for 5 trios of tables : “master”, “images” and “categories”. They are pretty much the same, except the table and field names. To do that, let’s play with abstraction.

I’m using crude ViewModels to display my search pages. They get the elements to display in the search dropdown lists, and paginate the results. All of the logic is in the constructor (the viewmodel is only used to display a search screen). When the constructor needs to get specific elements, it calls abstract methods. They are the ones that are actually different in the various pages.

The abstract base looks like this :

And now the implementation is very simple ; here for the themes :

Theme_Combination is the joining of two entities, Master and Images. All your element_combination must inherit from IElementCombination. If they do not implement anything specific themselves, you can even use a single ElementCombination class.