One of the techniques I recommend highly in my Simplify Your API talk is the use of extension methods to hide the complexity of lower-level API functionality.  A good example of a place to use this methodology came-up last night in a great Reflection talk by Jeremy Clark (Twitter, Blog) at the NorthWest Valley .NET User Group

Jeremy

Jeremy was demonstrating a method that would spin-through an assembly and load all classes within that assembly that implemented a particular interface.  The syntax to do the checks on each type were just a bit more obtuse than Jeremy would have liked them to be.  As we left that talk, I only half-jokingly told Jeremy that I was going to write him an extension method to make that activity simpler.  Being a man of my word, I present the code below to do just that.

Tags: , , , , , , , , , , | Categories: Development Posted by bsstahl on 10/15/2016 3:56 AM | Comments (0)

I often hail code coverage as a great tool to help improve your code base.  Today, my use of Code Coverage taught me something about the new .NET Core tooling, and helped protect me from having to support useless code for the lifespan of my project.

In the code below, I used a common dependency injection pattern. That is, an IServiceProvider object holding my dependencies is passed-in to my object and stored as a member variable.  When a dependency is needed, I retrieve that dependency from the service provider, and then take action on it.  Since there is no guarantee that the dependency I need will have been placed in the container, I use some common guard logic to protect my code.

templates = _serviceProvider.GetService<IEnumerable<Template>>();
if ((templates==null) || (!templates.Any(s => s.TemplateType==ContactPage)))
    throw new TemplateNotFoundException(TemplateType.ContactPage, string.Empty);

In this code, I first test that I was able to retrieve a collection of Template objects from the service provider, then verify that the type of Template I need is present in the collection.  If either is not the case, an exception is thrown.

I had two tests that covered this section of code, one where the collection was not added to the service provider, the other where an empty collection was added.  Both tests passed, however, it wasn't until I looked at the results of the Code Coverage that I realized that the 1st test wasn't doing what I thought it was doing.  It turns out that there is actually no way to get a null collection object out of the Microsoft.Extensions.DependencyInjection.ServiceProvider object I am using for my .NET Core apps. That provider simply returns an empty collection if there isn't one in the container.  Thus, my check for null was never matched and that branch of code was never executed.

Based on this new knowledge of the behavior of the IServiceProvider, I had a few options.  I could:

  1. Rewrite my test to check for an empty collection.  This option seems redundant to me since my check to see if the container holds the template I need is really what I care about.
  2. Leave the code as-is just in case the behavior of the container changes, accepting that I have what is currently unnecessary and untestable code in my application.  I considered this option but it seems to me that a better defense against the unlikely event of a breaking change in the IServiceProvider implementation is described below in option 3.
  3. Create a new test that verifies the behavior on the ServiceProvider that an empty collection is returned if no collection is supplied to the container.  I am not a big fan of this option since it requires me to test OPC (other people's code), and because the risk of this type of breaking change is, in my opinion, extremely low.
  4. Remove the guard code that tests for null and the test that supports it.  Since the code is completely unnecessary, the test itself is redundant because it is, essentially identical to the test verifying that the template I need is in the collection.


I'm sure you've guessed by now that I selected option 4.  I removed the guard code and the test from my solution.  In doing so, I removed dead code that served no purpose, but would have to be supported through the life of the project.
   
For those who might be thinking something similar to, "It's nice that the coverage tooling helped you learn about your code, but using Code Coverage as a metric is actually a bad idea so I won't use Code Coverage at all", I'd like to remind you that any tool, such as a hammer or a car, can be abused. That doesn't mean we don't continue to use them, we just make certain that we use them properly.  Code Coverage is a horrible way to measure a development team or effort, but it is an outstanding tool and should be used by the development team whenever possible to discover things about the code base.

Tags: , , , , , , , , , , | Categories: Development Posted by bsstahl on 10/27/2015 3:43 PM | Comments (0)

I don't create collection objects anymore.

I know, I know. I was they guy always preaching that every entity that was being collected had to have its own collection object. It was the right thing at the time; if you needed to take an action on an enumeration or list of objects, those actions needed to be done within a strongly-typed collection object to maintain encapsulation. Even if all that was happening was that an inherited List<T> function was being called, that functionality needed to be called on the TCollection object because, if it wasn't, it was likely that the next time logic needed to be performed on the collection, there wouldn't be a place to put it. Collection logic would end up being spread-out around your code rather than encapsulated in the collection. It was also possible that the implementation might change and need to be updated everywhere, instead of in one place.

Today however, that has all changed. Extension methods now allow us, at any time, to add functionality to ICollection<T>, IList<T>, IEnumerable<T> or any other interface or class. We can attach our list or enumeration based actions directly to the list or enumeration class, and do so at any time, since the methods appear the same to the developer as methods directly on the collection type. Thus, the "no place to put it" fear no longer exists. I've even started using this technique for my factory methods to make it clear that what I am creating is, in fact, an IEnumerable<T>, as shown below.

    var stations = (null as IEnumerable<Station>).Create();
    var localStations = stations.GetNearby(currentLocation);

In this example, both the Create and GetNearby methods are extension methods found in a static class called StationExtensions.

So, the big advantage here is that these methods can be added anytime, meaning we don't need to create an object that we MAY need in the future. This is better adherence to the YAGNI principle so it is a better pattern to follow. But what about disadvantages? Does it hurt us in any way to perform our collection actions this way? I'm not comfortable answering that question with an absolute "no" yet because I don't think I've been using this technique long enough to have covered enough ground with it, but I can certainly say that I haven't found any disadvantages yet. It seems like these extension methods are basically perfect for this type of activity. These methods do everything that the methods of a collection object do, can (and should) be put in a separate module to keep the code together, can be navigated to by Visual Studio in the same way as other methods, and have the same access (private, internal, public) restrictions that collection objects have. About the only thing I can say that is not 100% positive about using these techniques is that the (null as IEnumerable<T>) syntax to create a local variable instance to call the class factory from is not quite as elegant as I'd like it to be.

So you tell me, do you still create collection objects? Have you found any reason why using extension methods in this way is not as good as putting those methods into a strongly-typed collection? Sound off on Twitter and let's talk about it.

Tags: , , , , , , , , , , , , , | Categories: Development Posted by bsstahl on 7/11/2014 8:53 PM | Comments (0)

I recently started working on a set of open-source projects for Code Camps and other community conferences with my friend Rob Richardson (@rob_rich). In addition to doing some good for the community, I expect these projects, which I will describe in more detail in upcoming posts, to allow me to experiment with several elements of software development that I have been looking forward to trying out. These include:

  • Using Git as a source control repository
  • Using nUnit within Visual Studio as a test runner
  • Solving an optimization problem in C#
  • Getting to work on a shared project with and learning from Rob

As an enterprise developer, I have been using MSTest and Team Foundation Server since they were released. My last experience with nUnit was probably about 10 years ago, and I have never used Git before. My source control experience prior to TFS was in VSS and CVS, and all of that was at least 6 or 7 years ago.

So far, I have to say I'm very pleased with both Git for source control, and nUnit for tests. Honestly, other than for the slight syntactical changes, I really can't tell that I'm using nUnit instead of MSTest. The integration with Visual Studio, once the appropriate extensions are added, is seamless. Using Git is a bit more of a change, but I am really liking the workflow it creates. I have found myself, somewhat automatically, committing my code to the local repository after each step of the Red-Green-Refactor TDD cycle, and then pushing all of those commits to the server after each full completion of that cycle. This is a good, natural workflow that gives the benefits of frequent commits, without breaking the build for other developers on the project. It also has the huge advantage of being basically unchanged in a disconnected environment like an airplane (though those are frequently not disconnected anymore).

The only possible downside I can see so far is the risk presented by the fact that code committed to the local repository, is not yet really safe. Committing code has historically been a way of protecting ourselves from disc crashes or other catastrophes. In this workflow, it is the push to the server, not the act of committing code, that gives us that redundancy protection. As long as we remember that we don't have this redundancy until we push, and make those pushes part of the requirements of our workflow, I think the benefits of frequent local commits greatly outweigh any additional risk.

As to the other two items on my list, I have already learned a lot from both working with Rob and in working toward implementing the optimization solution. Even though we've only been working on this for a few days, and have had only 1 pairing session to this point, I feel quite confident that both the community and I will get great benefit from these projects.

In my next post, I'll discuss what these projects are, and how we plan on implementing them.

Tags: , , , , , , , , , , , , | Categories: Development Posted by bsstahl on 2/28/2013 6:34 PM | Comments (0)

or, How I found my Passion for Windows 8 Store App Development

Update: My first Windows Store app was published on March 27, 2013 and can be found here.

I don't have any apps in the Windows 8 Store yet. For that matter, I don't have any apps in the Windows Phone store, or the Apple or Android stores either. I have many ideas for apps, and a number of them in the works for both Windows 8 and Windows Phone, but I have nothing real to show for it yet. Nothing to show for several years of attending sessions at conferences, user groups, and code camps on building these apps; for many hours of hacking on front-end interfaces and business logic. Don’t get me wrong, I've wanted to build these apps, but I didn't have that burning desire that I usually get when I am solving problems with software. You know that desire, the one that compels you to sit in front of a computer for hours at a time until you've completed a solution. I didn't have it.

This recently changed for me -- let me explain.

I have spent most of the last 20 years building enterprise web applications that do most of the work on the server side. My user interfaces have been built in HTML, with some JavaScript for validation and Ajax for dynamic post-backs, but all business rules were housed entirely on the server in either C#, VB or something similar. Even before .NET, in the classic ASP days, my logic executed on the server with VBScript calling components created in Visual Basic. Before that, it was Pascal programs spitting out pure HTML to the console which was then redirected to the browser stream by the web server. As a result, I am very comfortable with using HTML for layout, and multi-purpose languages like C# and VB.Net for the business logic and data access.

In the app world however, this combination of technologies has seemed out-of-reach. In Windows Phone development, I could use C#, but needed to use XAML for layout and style, a technology that I have not yet been able to get comfortable with. For Windows 8 store apps there are more options, including HTML5/JavaScript apps, but I have never been comfortable writing code in JavaScript. The advent of TypeScript has brought us even closer to a solution in my comfort zone where I can get almost a C# style experience with HTML5 as my layout mechanism, but I am still missing key features like LINQ and generics.

Enter Windows Runtime Components. I say “enter”, as if they were new -- they're not, I just apparently allowed myself to forget about them. RT Components can be written in C# (and other languages), but can be called from JavaScript or any Windows 8 Store code, just as if they were written in that same language. RT components can also call into any .NET code that can be executed in a Windows Store App. As a result, I have the power of C# and the .NET Framework at my disposal while writing a JavaScript app. All I have to do is wrap my .NET Windows Store compatible libraries in an RT component, and use JavaScript to bind it to my HTML layout. Since I have been using Portable Libraries for most of my business logic for some time now, and those libraries that aren't yet portable, are generally easily translated, most of my .NET business logic is already available for me to wrap in an RT Component.

With the primary business functionality done in C#, it becomes a relatively trivial exercise in JavaScript to bind my RT model to the HTML components in my UI. This experience is completely comfortable to me, and in using this process, I have found the passion I was missing for building these apps. I will have several apps in the Windows 8 store in the next few weeks with more to follow after that. I will also be writing about my methods in building these apps, from the perspective of an enterprise developer. Hopefully, this will allow others to find the passion for creating these apps as I have. In the meantime, here are a few tips you can start using now to ease the transition into building apps:

  1. Use portable libraries wherever possible, especially for business logic.
  2. Use dependency injection to make non-portable dependencies available to portable libraries. This will allow your business logic access to platform-specific functionality (such as network access) without sacrificing portability.
  3. Do as much of the work as possible in the underlying .NET libraries and keep the RT Component as thin a translation layer as possible. I will be exploring techniques for this in the near future. Possibilities here include making this layer either a View-Model or a Repository implementation.
  4. The only logic in the JavaScript code should be that which is required to bind the RT Component to your controls. If you are doing more than setting event handlers and other control properties in your JavaScript, you might want to think about moving that functionality into a lower layer. This has the added benefit of making that logic potentially reusable across applications.

I’m interested to hear if there are other enterprise developers with similar stories, whose comfort zones of HTML and C# or VB have kept them from building apps as they’d like. Please contact me on Twitter at @bsstahl.

The complete, working application for my .NET TDD Kickstart sessions can be found here.

Unzip the files into a solution folder and open the Demo.sln solution in a version of Visual Studio 2010 that has Unit Testing capability (Professional, Premium or Ultimate).  Immediately, you should be able to compile the whole solution, and successfully execute the tests in the Bss.QueueMonitor.Test and Bss.Timing.Test libraries.

To get the tests in the other two test libraries (Bss.QueueMonitor.Data.EF.Test & Bss.QueueMonitor.IntegrationTest) to pass, you will need to create the database used to store the monitored data in the data-tier and integration tests, and enable MSMQ on your system so that a queue to be monitored can be created for the Integration test.

The solution is configured to use a SQLExpress database called TDDDemo.  You can use any name or SQL implementation you like, you’ll just need to update the configuration of all of the test libraries to use the new connection.  The script to execute in the new database to create the table needed to run the tests can be found in the Bss.QueueMonitor.Data.EF library and is called QueueDepthModel.edmx.sql.

You can install Message Queuing on computers running Windows 7 by using Programs and Features in the Control Panel.  You do not need to create any specific queue because the integration test creates a queue for each test individually, then deletes the queue when the test is complete.

If you have any questions or comments about this sample, please start a conversation on Twitter or Contact Me.

I head out to Fullerton tomorrow for the start of my .NET TDD Kickstart world tour Smile

In this session, the speaker and the audience will "pair up" for a coding session which will serve as an introduction to Test Driven Development in an Agile environment. We will use C#, Visual Studio and Rhino Mocks to unit test code to be built both with and without dependencies. We will also highlight some of the common issues encountered during TDD and discuss strategies for overcoming them.

I will be presenting this session at numerous venues around the country this year, including, so far:

If you are interested in having me present this or another session at your event, please contact me.

There is much more than an hour’s worth of material to be presented, so instead of trying to rush through everything I want to talk about during this time, I’ve instead taken some questions from this presentation and posted them below.  Please contact me if you have any additional questions, need clarification, or if you have an suggestions or additions to these lists.

Update: I have moved the FAQ list here to allow it to be maintained separately from this post.

I previously posted the slides for my Building Enterprise Apps using Entity Framework 4 talk here.  I can now post the source code for the completed demo application.  That code, created for use in Visual Studio 2010 Ultimate, is available in zip format below.  This is the same code that was demonstrated at Desert Code Camp 2011.1 and SoCalCodeCamp 2011 as well as the New Mexico .NET User’s Group (NMUG).

EF4EnterpriseDemoCode.zip

Tags: , , , , , , , , | Categories: Development Posted by bsstahl on 3/9/2011 3:31 AM | Comments (0)

Anyone who uses code generation more than trivially in their .NET solutions knows how difficult it is to add metadata to a member of a generated class, even if that class is marked as partial.  Partial classes are terrific for adding members to generated classes, and even allow you to change metadata and other information about the class itself, such as by adding an interface that it implements.  You cannot however, modify an existing member of the class by marking it to not be serialized, or to make it a part of a WCF data contract. I believe, as more and more code is generated by .NET developers using Entity Framework, wsdl.exe and other proxy generation tools, or even T4 directly; we will see a greatly increased need for a workable solution to this problem.

The most common work-around for this problem today is the use of “buddy classes” where a separate class is created to hold the metadata.  A good example of this type of solution can be found in ASP.NET Dynamic Data.  However, as you might imagine, this type of implementation has some fairly severe drawbacks.  For one, it requires some sort of mechanism for unifying the functionality of the two classes. An example of this is the case where we have a property on an Entity Framework POCO that should not be serialized when we serialize the rest of the class.  We cannot serialize the POCO correctly unless we use a custom serializer that is aware of the metadata in the buddy class.  We have similar problems if we are trying to use a generated base class as the output of a WCF service.  If the [DataContract] attribute is not already on the generated code (which requires a reference to the System.Runtime.Serialization library) we will have to create a separate object that implements the DataContract to be exposed by the service.  In most cases, this object will be an almost exact duplicate of the state features of the original object, forcing the replication of some code, even if that code is just the properties of the object.

There is a feature that has been proposed in the C# language for some time now that would allow this type of behavior within a single class.  This feature would use the keyword existing to allow the duplication of the definition of partial class members into non-code-generated files so that those members can be decorated with additional metadata without risk of being overwritten when the automatic code is regenerated, and without duplicating the functionality in the member.  Unfortunately, it appears that this feature is not going to make it into the next version of C# and is at risk of not being in the following version as well.  In an email exchange, Mads Torgersen, C# Program Manager at Microsoft, stated that

…maybe we’re looking at C# next-next-next before the next big set of new feature ads makes it in [to the language]. 

One of the reasons (although certainly not the only reason) for this delay, as explained by Mads, is what really struck me:

To be honest the clamoring for the “existing” feature has died down quite a bit. I think that people are probably resigning to the use of “buddy classes” for this purpose; this seems to be the most common substitute.

Mads continued:

…ultimately your feedback is at the basis of how we make these choices.

So I began to wonder, have we really resigned ourselves to using these buddy classes?  Are they less of a problem for others then they are for me?  Am I, perhaps, missing a fairly easy solution to this problem that involves the use of “buddy classes” but solves the issues with that methodology?  Or perhaps, are there other features that we want in the language that are just more important to us than this one?

Please let me know if am I missing something or if there are others out there who feel as I do on this feature request.  If there are many others like me, perhaps we can put our voices together to, as Mads suggests,  let Microsoft know what we need.

Tags: , , , , , | Categories: Development Posted by bsstahl on 11/13/2010 5:45 AM | Comments (0)

Since I’m a fan of puzzles, I’ve been spending a bit of time on http://PexForFun.com lately.  This site was put together by the Pex team (part of Microsoft Research) to show off the capabilities of some of the research group’s  latest creations; Pex, Moles, and Code Contracts.  I’ve been enjoying this site because it gives me the opportunity to solve some coding puzzles, while at the same time discovering things about these new tools.  Today alone, I discovered the following:

The order of Contract.Requires() in Code Contracts matters.

Though it doesn’t seem like it should matter (at least to me), the order that code contracts are specified does seem to matter at execution, at least in some circumstances, if runtime checking is enabled.  For example, in my ChallengeAuction code duel there is a practical limit to how many bids may be supplied since Pex has to test each of the data elements.  Defining this limit in as a Contract.Requires() element works well as long as that statement is placed before a statement testing the data elements, such as one verifying that the key for each bid is not an empty string.  Reversing the order of these contract statements causes the test to occur for each data element of the dictionary, and a “path bounds exceeded” error to be generated by Pex.

Pex doesn’t generate more than 1 Dictionary value for any test dataset.

The same code duel, ChallengeAuction pointed out to me that apparently, Pex only generates 1 data element in a dictionary.  That is, in the Dictionary<TKey, TValue> defined for bids in the code duel, Pex generates a Dictionary object of various sizes, but only supplies 1 data element within the Dictionary.  This means that a number of code paths are not being verified since it is important in this duel to test whether or not the highest bid wins the auction.  If you try the duel, you could actually fool Pex into thinking you have a successful solution even with a method that returns the lowest or first bids as the winning bid. 

I have posted this as a question on the Pex and Moles PowerTool forum and have yet to receive a response.

 

I highly recommend checking out http://PexForFun.com.  Try a few code duels and perhaps create a few of your own.  I have created several code duels which you are welcome to try and solve:

FabulousMrFib | ChallengeEarnies | ChallengeAuction | ChallengeContractSubstring