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 6/28/2013 1:05 AM | Comments (0)

On at least 2 occasions recently, I have heard speakers tell their audience that you cannot reference a target-specific .NET library (such as a .NET Framework 4.5 library) from a Portable Class Library. While this is technically true, it doesn't tell nearly the whole story. Even though we can't reference target-specific libraries, we can still USE these libraries. We can call their methods and access their properties under the right circumstances. We can gain access to these libraries via an abstraction. My preferred method of doing this is known as Dependency Injection.

I'm going to give some quick background on PCLs and DI before getting into the details of how they can be used in this context. If you are familiar with Dependency Injection and .NET Portable Class Libraries you can skip these sections.

.NET Portable Class Libraries (PCLs)

Portable Class Libraries are .NET assemblies designed to be used by multiple target platforms in the .NET application space. You can specify which targets you want to be able to use, such as .NET 4.5, Silverlight 4, Windows Phone 8, etc. The compiler then does the work to limit the APIs you have at your disposal in that library to only the intersection of all of the selected targets. This guarantees that any code written in that library will work in all of those targets, but no target-specific (device-specific) functionality will be available. These libraries are great for business-logic and other platform-independent services but are not useable for code that requires direct access to device features like the UI, camera, GPS, etc. This code can be compiled and tested once, and then accessed from any of the selected target contexts.

Dependency Injections (DI)

Dependency Injection is a way of maintaining loose-coupling between application components. Instead of having a piece of code have a direct knowledge of one of its dependencies, the code only has knowledge of an abstraction of that dependency, usually an interface. Since the client is unaware of the implementation and only has knowledge of the abstraction, the implementation of the dependency can change, and as long as it maintains compliance to the interface, the client code is unaware of the change and continues to function normally. The correct dependency must then be "injected" into the calling code prior to being used. The client only knows that the dependency implements the needed interface, but is unaware of the actual implementation. This becomes extremely useful in unit-testing since a fake dependency such as a mock data-provider can be injected by the test context, allowing the tests to focus on the layer being tested without having to test the dependencies as well. While this is not nearly the only reason to use DI, it is an example of an excellent benefit of its use.

Injecting Target-Specific Code into PCLs

Let's suppose we have a .NET Portable Class Library that implements the business logic of our application. We want the application to be able to run on the web under ASP.NET, on Windows 8 as a Modern Windows Store App, and on Windows Phone 8. We built the PCL using these specific targets so we know (the compiler guarantees) that this code will run in any of those platforms. However, this code needs to get its data from somewhere, and that somewhere is different depending on what environment we are running in. In ASP.Net for example, we may want to get the data from Session State, or from a back-end SQL Server, while in Windows Phone 8 and Windows 8 we want to use their (different) implementations of isolated storage. We can accomplish this by defining an interface that is usable by all 3 targets in a PCL. We can then create our 3 different implementations of the storage library using target-specific code and inject the appropriate one into the constructor of one or more of the classes in the business-logic PCL. This injection can be done directly by the parent application, which is going to be target-specific so it would have knowledge of which target is needed, or it can be done indirectly using a DI Container such as Microsoft Unity.

A sample app that is available in the 3 targets previously described may look something like this. The business-logic and domain layers (interfaces, exceptions, entities, etc) are both PCLs and exist for use in all 3 targets. The UI layer and Infrastructure layers (in this case, storage) are target-specific and require a separate implementation for each target platform. A system designed in this way can maximize the use of common, shared code while still making platform specific features available in a type-safe way.

If you are interested in seeing this implementation done live, you can come to one of my Code Camp talks on the subject, or request me as a speaker for your User Group via Ineta.

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.

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: Event Posted by bsstahl on 1/31/2011 12:50 AM | Comments (0)

I won’t be an attendee at Mix this year.  Nothing against the conference; it is usually fantastic and I have met many awesome people there.  This year, my focus is elsewhere, on SOA and Middleware/Back-End technologies.  Not that I’ve ever really been a front-end guy mind you, but I am of the opinion that balance is a good thing and since I consider myself weaker in front-end (UX) technologies, Mix has been a good learning experience for me in the past.  However, as I said, this year, my primary focuses are elsewhere. 

Not being an attendee doesn’t stop me from wanting to meet with old friends and continue the awesome technical discussions that go on at these events.  I have loved meeting with the product teams in the past, both to learn from them and to provide my input into the future directions of the products.  So, it is my intent to fly up to Las Vegas (it is less than an hour flight from Phoenix) for at lease 1 evening of the Mix conference, perhaps 2.  Right now, I am looking for events to schedule for that (those) evening(s).

I know that I will not be able to go to the attendee party, since I will not be an attendee, and that event occurs on Wednesday the 13th  (courtesy of Joe Guadagno’s Mix 11 Events site).  This means that the most likely evenings for me to be there are Monday and Tuesday, April 11th and 12th.  Do you know of any events going on in Las Vegas during this time that would be awesome for me as a .NET Software Engineer to attend?  If so, I would appreciate it if you would let me know.  I’ve setup a special email alias just for this purpose, please contact me at bss_MixEvents@bsstahl.com.

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

Tags: , , , , , , | Categories: Development Posted by bsstahl on 3/7/2009 9:32 PM | Comments (0)

The following statement builds a C# string containing an Oracle SQL query that uses a DateTime specified in the .NET code.  It uses the Oracle TO_DATE function to convert the string date to an oracle date object and specifies the format of the string date for both the C# output and the Oracle input. Using this statement, there can never be a date format mismatch since the same format is specified at both ends.

string sql = string.Format("select * from MyDB.MyTable t where t.MyDate > 
     TO_DATE('{0:MM/dd/yyyy hh:mm}', 'MM/dd/yyyy HH24:mi')", DateTime.Now);

I have found myself using this type of statement fairly often to create tools that help me do my job.  For what it's worth, I wouldn't put this type of code in production since you rarely want to execute a query from a string in a production environment.

Tags: , , | Categories: Development Posted by bsstahl on 4/29/2006 1:47 PM | Comments (0)
I am seeing some things in .NET 2.0 that concern me. Much of it has to do with Microsoft putting in features that have obviously been demanded by many developers, but were not included in earlier versions of the framework because, for the most part, they are the wrong thing to do the majority of the time. For example, Microsoft has included the ability to have inline code as well as the standard code-behind model in ASP.NET 2.0 pages. While this seems like a nice feature, I can't come up with a good reason to ever mix my object code and HTML code. Perhaps someone else can. If you do, please let me know.
Tags: , , | Categories: Development Posted by bsstahl on 4/29/2006 3:52 AM | Comments (0)
Another feature that concerns me (see my earlier post) is .NET Generics. While it is nice to be able to specifiy a strongly-typed collection without having to create a class, it seems to me like this is still the house of sticks, rather than the house of bricks we really want. Also, extensibility seems to suffer in this model because we are limiting our encapsulation. I certainly have not used this enough to say one way or another for certain, I just currently have concerns.