At last, the final video in this series on pattern-based XML literals. That culmination of all my machinations! Last time I showed you all some example web controls—classes that know how to render their behavior using the standard web primitives of HTML, CSS, and JavaScript. The next logical conclusion is knowing how to render VB.NET itself to JavaScript. Check out this video as I run through three examples.

This isn’t anything radical (outside of the common use of the word meaning cool, in which case yes, it is!). This is the same technique developers all over the world use every day with LINQ and Entity Framework. Leveraging expression trees to write code in VB.NET that is then transformed into SQL and executed on another machine. I’m using those same capabilities to let me write glue code with the same convenience.

And to be clear, this is the exact same pattern I used for my Xamarin post last month. I haven’t changed it to support this new use. It’s just sufficiently flexible that it could enable this “out of the box”, so to speak. You see, because the XML pattern can instance and initialize arbitrary types, when those types make use of other types like System.Linq.Expressions.Expression that rich information is available to the compiler so things like the natural ability to convert to lambdas to expression trees just “falls out”, as we say.

An interesting bit of trivia: Originally, I did plan on (and I am proposing) extending the currently limited set of language constructs supported by expression tree conversion. However, I did not have to extend it nearly as much as planned. 1) Statement (Sub -> Action) lambdas are already convertible to expression trees in a very few cases, 2) I was surprised to learn that assignment is one of those cases if and only if the target of the assignment is a property. I’ll add that to “The List”. So, for this demo I just relaxed the restriction that syntactically the lambda had to be a single line lambda just to further clarify for viewers that this is an assignment, not a comparison. But even without that, the ingredients are all there.

The product of the whole is much greater than the sum of the parts

This is the power of orthogonality in language design. Every feature doesn’t have to be “big” if a number of smaller seemingly less sensational features can work together to produce a great result.

• Top-level code has been independently requested throughout the years; it’s not a “big” feature to design or implement nor a massively disruptive addition to the language.
• XML literals were added to the language over ten years ago with a narrow focus on providing a declarative syntax for using the XLinq API; it’s not a radical suggestion to generalize this useful albeit niche feature to bring that declarative productivity to other types.
• Expression trees have also been around for a decade and members of the community have independently suggested extending the languages to support more of constructs on multiple occasions throughout the years.  

Each of these is a mere evolutionary step of 10, rather than a revolution step of 100 but 10 x 10 x 10 is 1,000! And if you think about adding JSON literals to the mix there might be even greater rewards!

What’s next?

Somewhere out there in the VB web development community is the author or authors of the next built-for-VB web framework a la DotNetNuke (originally written in VB.NET) or Suave (built for F#). My question to those community members is:

• If you had a language with the richness of capabilities and tooling like VB.NET—things like Async/Await, string interpolation, and LINQ
• And that language was homoiconic—you could easily get a data structure representing the code written in that language to manipulate and even translate as you see fit
• And that language could natively describe the two most important data structures on the modern web, the DOM (via XML literals) and JSON (via JSON literals)
• What could you do with that?

I’m personally very excited to find out!

Summary

For a few years now I’ve been wrestling with the growing complexity of modern development. It’s pretty obvious that on top of HTML, CSS, often SQL, sometimes RegEx, managing two general purpose imperative programming languages on the client and server respectively is less than ideal. JavaScript developers who want to use JavaScript on the client and server can use Node.js. VB.NET developers who want to use VB.NET on the client and server need a solution. For me it’s a big productivity boost. But for a new VB.NET developer deciding whether to start prototyping their idea in WinForms where the just have to learn one language or the web where they have to learn 3 languages, 4 frameworks, 2 package managers, … you can see why a lot of people start in WinForms even now. I love WinForms, I want to love web development too! Pattern-based XML literals will be a powerful first step in reigning in some of the complexity and I hope this post/video gave you a glimpse into how.

I’m certain I’ll probably do a one-off post showing more on this topic in the future but this wraps up the series about this prototype. I’ll decompress my design notes on GitHub ASAP and post an update on this blog when that’s done. I absolutely want to discuss a whole bunch of interesting design questions about a hypothetical VB.NET web app framework built using the techniques I’ve shown in these last two posts, but I want to be clear that that effort is orthogonal to this feature. To that end I’ll decompress a separate set of thoughts about it specifically in the post after my next one.

Until then, as always, thanks for reading, thanks for watching, please share this post, and let me know your thoughts in the comments below and/or on Twitter.

Regards,

-ADG

P.S. I really wanted to post this back to back with my last post but due to several surprised visits, I’ve had out of town house guests every week of this month. As much as I wanted to be a terrible host and neglect my friends and family to tweak my expression tree -> JavaScript visitors I failed to do so. Yesterday and today I was finally able to carve out a little time to record, edit, and upload the video and this post before even more out of town visitors arrive. Special thanks to my younger sister who is patiently waiting in another room for me to hit Publish so we can go get some breakfast.

This is my third post in this series about pattern-based XML literals. In my last post I showed how you could apply the concept to the Xamarin.Forms library via extension methods to build a cross-platform mobile app in VB using what are essentially “XAML literals” to describe your UI. In this post I’m revisiting the web and showing how someone could use the exact same pattern to not only make a dynamic ASP.NET Core MVC app but how to do so while reducing code by 50-80% using one classic idea!:

Yep, web controls. I know. But these aren’t like the ASP.NET WebForms web controls. There’s no view state or post-backs here; it’s still all MVC. These controls just know how to render themselves and that counts for a lot!. And, as I said earlier, this is the same XML-pattern at the language level that I used in my Xamarin video, the only thing that’s changed is the types that are being constructed (and they were built with the pattern in mind so no need for extension methods). Also, I temporarily merged in my top-level code prototype to get back that sweet full-file top-level XML expression experience! I didn’t change the pattern any, which is a good sign.

My personal rematch with an old challenge from the early 2000s…

From September 1999 to June 2003, I was in high school (I’m currently 34 for those of you doing the math). I was in our high school computer club, tasked with building what was then our high school website. I wanted to liven up the site with “DHTML” (i.e. JavaScript) that would create a drop-down menu instead of requiring navigating the site through clicking through a tree of links. I thought I was soo cool.

I got some examples off of some website, (it might have actually been called dhtml.com or something) but the menu was soo tedious to implement. I vaguely recall making a VB6 app that would generate the menu from an indented text file, it was that tedious. Compare my high school experiences with this declarative masterpiece:

Full comparison of source code and HTML output here.

A Declarative and Object-Oriented Approach

Even just using plain HTML/CSS/JavaScript, it’s gotten better (and I’ve gotten better) but the web can still be pretty tedious compared to what I’m used to and love about traditional desktop app programming. Sure, HTML is declarative but depending on what you have to declare one person’s declarative is another person’s spaghetti-code and generating certain common, exciting, interactive web experiences can easily liter you page with tons of implementation details.

Encapsulation FTW

Pattern-based XML literals let me use my object-oriented instincts of abstraction and encapsulation in a crazy-productive declarative way. And I actually experienced one of the benefits of this encapsulation immediately first hand. While writing the carousel example I started from the ASP.NET Core sample but later moved to the w3schools example because one of their pictures was named “Chicago.jpg”. Little did I realize that the W3Schools was using Bootstrap 4 while the ASP.NET Core sample I had started with was using Bootstrap 3. Well, in between 3 and 4 Bootstrap changed a few things (understandably):

1. The CSS classes for carousel items went from class=”item” to class=”carousel-item”
2. The CSS classes for carousel controls went from left carousel-control to carousel-control-prev
3. The glyphicon library that had previously been included by bootstrap no longer was so the carousel controls which used it no longer rendered correctly.

In short, nothing worked. Had I been directly using this carousel code (or some other element) across a real site, at that point I’d have to manually go through all of my pages looking for divs with class “item” and manually update them—for EACH ITEM. Once I realized what was going on, I just updated my Carousel control class once to generate different output for items and I was done. Next run of the app the page rendered correctly without having to change any of the markup in my Index.vb file.

Summary

Controls are perhaps the most empowering abstraction to ever touch my life. Entire ecosystems of control creators and vendors sustained the VB community for decades. And a world where there aren’t re-usable control components to hide and handle basic rich UI experiences is an incredibly complex one that I’m not particularly interested in coding in.

Reducing complexity through abstraction, encapsulation, and polymorphism is a very object-oriented approach to the web. But to be able to use them it helps to have “objects all the way down” and traditionally that would mean giving up the declarative simplicity of markup languages like (X)HTML. With pattern-based XML literals that doesn’t have to be the case. This potential feature massively scales up the expressivity of the XML literal-based ASP.NET Core view engine I showed back in May and opens the door for even more cool stuff I’ll show in my next post.

I do want to talk about the idea of what a real (not made for demo purposes) web controls library would look like but that’s a separate conversation from discussing this prototype so I’ll be giving that topic its own post as well.

Until then, as always, thanks for reading, thanks for watching! Please share this post, and let me know your thoughts in the comments below and/or on Twitter.

Regards,

-ADG

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P.S. As in my last series, I’ll upload all of my notes from implementing the prototype in a GitHub issue after the last post in the series. Don’t sweat the specifics of the pattern too much, they’re subject to and very likely to change. This post took me much longer than usual because I had to take a refresher course on CSS, JavaScript, the DOM, and write an entire naive implementation of a self-rendering class hierarchy modeling all the HTML elements used in that video (don’t worry, inheritance took care of a lot of the work).

Credits to these sources for their help:

• W3Schools – Expander, Menu, Carousel examples. This site is an indispensable resource to all things web.
• HTMLDog – Multi-level Menu example.
• Jason Chatonda – Sound editing, because this video had a lot of esses in it. Imagine Daffy Duck soliloquizing on the superior splendiferousness of XML, expanders, menus, carousel scripts and CSS specificity.

In my last post I introduced the idea of pattern-based XML literals—XML literals which construct arbitrary types other than XDocument/XElement/XAttribute/etc. And as promised, I have recorded a video showing off the practical benefits of this design when using Xamarin.Forms from VB.NET. If you’re not familiar with Xamarin.Forms it’s an API that abstracts over the differences between mobile platforms like Android and iOS to make it easier to create and maintain cross-platform apps while sharing the maximum amount of code. Watch as I explore the Xamarin VB sample app from the official Xamarin samples repo using this new prototype:

As you can see, it’s pretty empowering to be able to use XAML everywhere.

• I can leverage my XAML skills from WPF to a degree and be more productive.
• If I’m looking at the documentation or a sample or blog post (most likely written from a C# developer) that uses XAML, I can use that XAML in my code rather than first translating it to VB imperative code.
• In places where today you’d possibly have to give up markup for code like dynamic view creation, I can still use declarative XAML even if it’s in the middle of a VB method (this scenario comes up in writing VS extensions to the WPF editor too).
• Even with object initializers there can be situations where you have to fallback to imperative syntax like using attached properties but that’s not an issue using markup.
• I get to embed any VB expression inside my markup in places where that expressiveness is a benefit over XAML.

WPF XAML vs Xamarin XAML

Xamarin has its own flavor of XAML. It’s essentially the same on the surface (syntactically) as what’s used in WPF and Silverlight (and UWP) but it’s not the same XAML engine and it uses different types internally. Not just in the “Controls” or as Xamarin calls them “Views” but in the infrastructure itself:

• So rather than DependencyObject and DependencyProperty, Xamarin has BindableObject and BindableProperty.
• Xamarin has its own base types for type converters, and markup extensions, etc.

So, even though both it and WPF use the XAML syntax (which is XML based), Xamarin.Forms is powered by a completely different engine entirely. Possibly as a consequence of this the XAML used by Xamarin.Forms doesn’t support VB.NET. Which would normally mean you have to create your UI imperatively, rather than declaratively. VB guru Klaus Löffelmann wrote about how to do this back in 2017 on the VB team blog. It was a good post but the no-XAML part was kind of a bummer. This prototype changes all of that!

The Xamarin differences actually highlight another benefit to being pattern-based. Because the language understands patterns—certain methods with certain names and shapes existing—rather than specific types (like DependencyObject) it’s possible to apply the feature to a completely different system than WPF. If the feature were just WPF XAML literals built to understand the specifics of the WPF infrastructure you couldn’t turn around and apply it to Xamarin but by being pattern-based you can do that easily.

Under the hood

As I indicate in the video, the compiler knows XML and how to translate certain idioms in XML into call-outs to extension methods that encapsulate all of the Xamarin-specific knowledge. I’m pretty sure the pattern will change as I explore more but the first page’s code:

Translates to this:

As you can see, the compiler knows how to translate attribute values to enum members at compile-time. So if I misspell and enum member I’ll get a compile-time error:

Likewise the compiler knows how to translate an attribute value to a delegate creation, so that too gets compile-time validation:

Both of these make it easy to give in-context completion support in the IDE for these cases.

The keen observer may have also noticed that when I selected name CalculateButton in the value of the Name attribute at around the 2:45 mark in the video that references to CalculateButton in code were highlighted. This is another example of the power of Roslyn. Because the compiler binds that text to the CalculateButton variable, the IDE understands it as such and features like Go-to-Definition work automatically!

THIS IS A WORK IN PROGRESS!!!

I accidentally edited out the part where I show what turns a regular XML literal into a pattern based one and it’s a magic "clr-namespace:" XML namespace import at the top of each file (could also be in a project-level import). If I comment out that import you can see that I get conversion errors because the XML reverts to producing an XElement as it does today:

I expect to find a better way to enable the feature though because of some trade-offs with that approach. This is just a draft version of the pattern and I fully expect it to change as I explore other shapes of XML to apply it to and weigh certain experiences that could be built.

For example, right now the pattern respects both a SetChildContent and AddChildContent bridge methods so that the compiler can report an error if you include more than one child element in a situation where only one child is allowed, but maybe it’s better to simplify the pattern and enforce things like that in a Roslyn Analyzer (let me know what you think).

If you’re really curious as to what each of these bridge methods looks like, I’ve uploaded the content of the XmlExtensions.vb file from the sample app I showed in the video as a Gist. It’s just what I wrote out while exploring the pattern and shouldn’t be taken as the “best way” to write such methods and I played around with different approaches. Just take it all with a grain of salt.

Next steps

I know Xamarin.Forms has been around for quite awhile now but honestly I haven’t been as excited to try it out until now. I can see some places where the Xamarin team made extremely reasonable choices in their content model (like how templating works). I’m anxious to see how I can broaden the pattern to work well with those patterns and to just generally explore mobile app development from VB.NET.

Fun Fact: Due to Windows Mobile and Compact Framework and then Windows Phone and Windows 10 Mobile, I have not owned a phone that I couldn’t program in VB.NET in almost 15 years. I’m excited to continue that tradition.

One thing this video didn’t show off was tooling. Because it’s all just the VB.NET language and the IDE is powered by Roslyn, getting things like completion, go-to-definition, F1 help, etc. to work in such XML literals is much easier than it would have been pre-VS2015. Also, there’s this other unrelated prototype I plan to show off… 4-5 prototypes from now that could really improve on both desktop apps using WPF/WinForms and mobile apps using Xamarin too. So whether it’s to show off better tooling, to show off another prototype, or just because I’m having fun exploring Xamarin.Forms I don’t think this will be the last video I make featuring this topic.

As for my next post it’ll be a continuation of this series about this prototype but instead applied to web development. I think you’re going to love it so look out for it.

Until then, as always, thanks for reading, thanks for watching, please share this post, and let me know your thoughts in the comments below and/or on Twitter.

Regards,

-ADG

P.S. As in my last series, I’ll upload all of my notes from implementing the prototype in a GitHub issue after the last post in the series. Don’t sweat the specifics of the pattern too much, they’re subject to and very likely to change. This post took me much longer than intended before the first few iterations of the video were over 30-minutes! It took some re-recording and aggressive editing to get it down to 5.X minutes, but I think that’s optimal for online viewing and sharing. I hope you agree!

“I have made this [letter] longer than usual because I have not had time to make it shorter.”
-Blaise Pascal

Hey all!

I’ve been down in the laboratory since my last post and I’m back with a brand-new prototype. I was working on scripting the first video for this prototype when I realized there’s just a lot of context to set beforehand so I’m taking a break to write a quick introduction.

What do I mean by pattern-based?

When I describe a language feature as “pattern-based” I mean that the feature is designed to work with any code that fits some pattern the compiler knows about rather than a specific limited predefined set of types. Not every feature is pattern based in VB.NET but several of them are. For example:

`For Each` doesn’t require a type implement `IEnumerable` (or that `IEnumerable` even exist) but rather that it meets the Collection pattern. A type is a Collection Type from the perspective of the compiler/language if it has an accessible `GetEnumerator` method that returns a type with a Boolean returning `MoveNext` method and a readable `Current` property and the `Current` property determines the type of the elements of the `For Each`. None of this requires `IEnumerable`, that’s just convenient and it means that library authors can write specialized enumerators which are more efficient in some way, usually by being structures rather than classes.

`Await` is another example. Everyone knows you can await `Task` and `Task(Of T)` but the language doesn’t require that, rather that the type have a `GetAwaiter` method that returns some type with the right set of members on it. If the type meets that pattern it is considered Awaitable. An example of this in action is the `Task.Yield` method which returns a `YieldAwaitable` structure, rather than `Task`.

Query comprehensions (the SQL-like LINQ syntax) aren’t tied to `IEnumerable` or even the `System.Linq.Enumerable` type either, but rather work on Queryable types—types which have a `Select` method that take a delegate that itself takes 1 parameter, the type of which is the element type of the `From` operator and may have other operators like `Where`, etc.

A big win from the pattern approach is that often a type can be made to support a pattern after the fact through an extension method. This is great when you don’t control the library that type is defined in but still want it to work well with new features. C# and F# also use this approach at times to varying degrees (F# turns it up to 11, actually). There are other features that use patterns (and ones that don’t) those are some big examples. Eric Lippert (of course) talked about some examples on his blog and one of the ones that don’t in either VB or C# (occasionally to my chagrin), the `Using` block.

Why?

Right now, XML Literals are in the ones that don’t bucket and I’m looking at what possibilities open up if that changes. These first three scenarios are minor. I definitely thought about them but I understand if they’re not top of mind of a lot of other people. They were stops along the train of thought. The last two though are pretty major so feel free to skip ahead if you aren’t interested in trivia.

Minor Scenarios

Windows Runtime/UWP XML

One of the first concrete scenarios I had was back when I was exploring the Windows Runtime/UWP library and I noticed that WinRT defines its own `Windows.Data.Xml.Dom` namespace which is, of course, not the `System.Xml.Linq` namespace that VB XML literals work with and I got to thinking, wouldn’t it be nice if VB could work natively with the WinRT types. If you look at the docs for creating live tiles and sending tile updates, the whole tile template system in Windows 8.x/10 is built on XML and their code examples look like they would benefit from XML literals and XML axis properties.

That’s one idea. It’s good language hygiene but fairly limited.

Rich WPF Message Boxes

I’m a big fan of Alan Cooper “Father of Visual Basic” (big surprise) and specifically his books on user experience like “The Inmates Are Running the Asylum” and “About Face: The Essentials of Interaction Design”. In one of those books he talks about message boxes and points out the ways software provides poorer, less situationally appropriate experiences because the default APIs are “good enough” and programmers just try to squeeze whatever problem they have into what the API provides rather than writing a custom dialog. It’s been years but I recall him showing an example of some program that wants the user to do one of two things and it puts up a dialog box that says something like “How would you like to proceed? Click ‘OK’ to file your taxes jointly or ‘Cancel’ to file separately with a 1099c extension”. Obviously, this choice shouldn’t be in terms of ‘OK’ and ‘Cancel’ but the programmer was too lazy to write the custom one-off dialog. The programmer has delegated mapping concepts from user-domain to the API to the user and that sucks.

The MessageBox.Show in WinForms and the other one in WPF are a little bit more customizable than this but sometimes I call MessageBox.Show and think “I wish I could provide a formatted string as the dialog text, maybe include some bolding or color or an image but the API just takes a string”. Ideally I’d be able to use all of WPF’s TextBlock primitives and just hand that to a generic built-in dialog presenter. I could write one, of course but there’s still some tedium to it because in my code I can’t use XAML, I have to imperatively construct a potentially elaborate object graph and that stinks.

XML-based DSL’s

If you look at the unit tests in the Roslyn source code, you’ll see thousands of examples of things like this:

The test team created these DSLs for setting up tests for the compiler and the IDE that other code then parses to create the actual test environment. XML has just enough structure vs strings while being flexible around multiline content. It’s neat and in a lot of places convenient to use XML to describe these test cases declaratively but it’s unfortunate that everything that happens in the XML literal is opaque to the compiler so you don’t get any tooling assistance at compile time. You could help this a little with analyzers but there are still seams in the experience.

Major scenarios

ASP.NET Core

In an earlier post I showed you how one could use XML literals to make a basic view engine for ASP.NET Core. It was nice but because it’s just producing an anemic XML DOM there are some limitations on how kick-ass it could be. I’m trying to see how far I can take it.

Xamarin.Forms

On the other side of the spectrum we have Xamarin.Forms. I’ve been interested in Xamarin for a few years now but one thing that bugs me is that to use it in VB I have to use code to construct my UI. I can’t use my XAML skills (until now).

So, I made a prototype…

The challenge is, can I come up with some reasonable pattern that would enable an XML literal to construct and/or interact with things other than the XLinq API. I’ve got a first-draft and some notes and a about 2-3 scenarios to show you based on what I came up with that I hope you’ll like. The first one up is the Xamarin scenario and it’ll be the subject of my very next post. I just wanted to get all the background out of the way so I can focus the video and the blog post on the scenario itself rather than general context setting.

Regards,

-ADG

At last we’ve come to the last of my planned scenarios for this prototype–a little thing I like to think of as a WYSIWYG Web Service, or WYSIWYGWS for short. A few months back I had recently finished the JSON literals post and video and was anxiously combing my immediate vicinity for more scenarios when Scott Hanselman came along quite serendipitously with his post, Converting an Excel Worksheet into a JSON document with C# and .NET Core and ExcelDataReader to inspired me.

I asked myself “How simple can defining a REST endpoint be?” and here is the result.

Of course there are myriad ways to approach this problem with various trade-offs, this is just one.

One developer on Twitter asked Scott (paraphrasing) “Why not just use PowerShell?”

To which Scott replies, “Very useful, yes, but would require additional PowerShell to get the output JSON I wanted”

Very useful, yes, but would require additional PowerShell to get the output JSON I wanted

— Scott Hanselman (@shanselman) March 12, 2019

And another developer says, what are the benefits of using ExcelDataReader over this PowerShell command?

And Scott reiterates, “Control over the result is all”

Control over the result is all

— Scott Hanselman (@shanselman) March 12, 2019

And that’s one key aspect to this scenario. Scott had an idea of what shape he wanted at the end and it was just a matter of getting what he had into that shape. And in the video above that’s exactly how I approach the problem as well, I start with that shape and then populate it. Now that’s what I call… Design by Contract! (ba dum chhh)

Another element to the scenario is data that is… uncooperative:

• You can’t control it
• You can’t annotate it serialization attributes
• The shape isn’t right for default serialization
• It’s coming directly from an external (not .NET objects) data source like a database, mainframe, device, other service, or in this case a file

And that last point is more important than you might think. Every day (on Facebook) I see a lot of developers working on apps that use DataSets as their data layer and/or are using an RDBMS that doesn’t have SQL Server’s fancy `FOR JSON` clause. Without getting into a big argument about whether those folk need to “Get with the times” and “Move everything over to X”, what’s the fastest way for them to Cloud- or Mobile-enable that data? And even if you do have POCOs for your domain-objects, there are a lot of reports in life and not every report deserves its own custom EndOfYearSalesByRegionReportRecordRow class just so you can use JSON serialization.

It’s also just a useful way and crazy easy way to mock up an service end-point. When I was exploring the GitHub Gist API I was very conscious of how my debugging might look to the GitHub service. Was I hitting the live API up too much? Will I hit a request limit? With this I can just go to a service, grab the output, and paste it and develop against that until I’m ready to hit the live service. Ease in testing is its own reward.

Conclusion

In my last post I combined top-level expressions with XML literals to create a basic VB.NET view engine for web pages on ASP.NET Core. In this post I took the same strategy but swapped out XML for JSON literals to make ASP.NET Core REST services a breeze in VB.NET. The approach has trade-offs and shines especially when dealing with one-off data sources such as files, database reports, and objects you can’t modify for serialization but yet still need to end up in a particular shape in the end, as well as testing.

So what about you?

Do you have any data you need to get out of some less that reputable places as painlessly as possible?

Does the low-ceremony abstraction I presented seem like the kind of thing that would make that easier or more attractive for you? Let me know in the comments below, or on Twitter.

Thanks for your time, your shares, and your feedback!

Regards,

-ADG

P.S. This is the last scenario 😥 in this series so my next post will be letting you know that the write-up of my design notes from exploring this idea have been posted on GitHub. Thanks for your patience!

In Scenario A I talked about the 1-line program—a single statement that prints the value of some expression to the console.

The next logical mental exercise (for me at least) is, “Gee, what if you get tired of typing Console.WriteLine all the time. Wouldn’t it be great if a program could be a single expression and the printing could all be handled auto-magically?”. I said it was a mental exercise, not a practical one 😊

Outside of making expression evaluator bots really simple that idea isn’t actually great at all, but patterns I came up with to approach it are useful for applications of other project types and many many lines of code. The Process looks something like this:

1. “What if a source file could be just a single expression?”
2. “You know what’s an expression in VB? XML!”
3. “XHTML 5 is XML”
4. <stuff>
5. This video of me demostraing a VB ASP.NET Core 2.0 MVC app with an XML literal-based “View Engine”:

Special shout-out to book author, former VB MVP, and current Microsoftie on the WinForms team, Klaus Löffelmann for doing the heavy lifting on creating the ASP.NET Core 2.0 Web API project sample I used to make this demo. It really distilled things to the bare minimum which was a huge help to me conceptually and also a great time saver!

What about “Razor”?

Here’s the thing about “Razor” (Is it a code-name, do I need quotes?). It’s an alternate view engine to ASP.NET Web Forms that aims for a particular aesthetic. That aesthetic has value but is definitely designed around C# (not dissimilar from the way Web Forms was designed around VB and Classic ASP). The Razor that is part of ASP.NET MVC 5 supports VB but the experience isn’t a bespoke VB experience. I’m pretty sure it doesn’t support VB XML literals at all (and I understand why) and that whole Code / End Code block syntax, while… well-intended does show the seams a little. And when we talk about ASP.NET Core there’s no vbhtml at all. I’m really not saying this to knock Razor at all. I think it’s cool. And as a guy who spent 5 years spelunking two parsers, I appreciate the challenges of building and maintaining a component that understands the nuances of code while the user is typing—a  problem that is even harder when the language itself is hosting another language nested in it (XML)—while also wanting to provide a great tooling experience. (I appreciate in part because I was working on Roslyn when the ASP.NET team was working on Razor and Web Matrix and they weren’t shy about telling us about the challenges 😉). And new language versions present new conflicts if new features don’t play in the way your view engine was coded to support: I mean, can you imagine what Razor would do if VB added JSON literals?

But, we (VB programmers) are in luck. Because Microsoft already owns an incredibly well-tested, well-oiled, well-maintained component that knows the ins and outs of the VB language and seamlessly transitions between VB, and XML, and interpolated strings, infinitely nested with an incredibly rich IDE experience just deeply integrated into it. It’s always maintained, it can’t fall out of sync with new features, and it’s basically free. It’s called Roslyn; we should use it!

Once again, as I did in Scenario B, I’m asking “What if we invert the problem?” and instead of getting VB into the views, we get views into the VB. Or better yet use what’s already in VB to make something idiomatic and aesthetically pleasing just for us at a comparatively much lower cost?

WWFSD—What Would F# Do?

Over the years since its introduction I’ve been continually impressed with the grace, creativity, self-reliance, and pioneering spirit with which the F# community has approached being unique members of the broader .NET community. It’s incredibly easy to assume that there’s only one way to approach programming and that it’s whatever the newest way Microsoft has released or whatever way C# is doing it because it’s intrinsically good for everyone and the best anyone can come up with for all situations (until the next thing comes out). F# is very good at remaining rooted in its own identity while looking for solutions to the same scenarios that C# or VB coders face but in a way that is complementary to and often strengthened by F#’s unique capabilities.

For example, Razor doesn’t support F# either but when I hear F# aficionados talk about web programming they aren’t talking about Razor, they’re talking about homegrown solutions like Suave and Fable and Giraffe and CloudButt and other made up names that are built with F#’s differences (read: strengths) in mind.

It is my sincere wish that we, the VB community, learn from their many examples and that one day we too have a catalogue of colorful names on a web page somewhere built by us for us. This is my opening contribution to what I hope will be an ongoing conversation.

Conclusion

I’ve still got one more scenario to post and then I’ll do the full write-up on GitHub the ins-and-outs of the proposed top-level code feature that made this video possible. Web programming is just one potentially application of it that I thought up but there’s another guy who’s been thinking on this topic a lot longer than I have, VBAndCs. I really wanted this scenario to be a surprise but VBAndCs saw it all coming in my comments section all the way back in Scenario B.

I have another planned prototype in my head that would go even further on this scenario that I hope to put out later and I’m really looking forward to seeing what awesome tailor-made experiences passionate folks in the VB-Web community like VBAndCs can build given the right language tools.

Share your feedback with me, share the video with your friends. And as always, thanks and see ya later!

Regards,

-ADG

Getting away from Console apps and Console paraphernalia, “Scenario C” is all about how top-level code can plug in to more interesting orchestrations.

Here’s a quick 5-minute video showing off top-level code forming the body of a game loop:

I really wanted to re-create the simplicity of my earliest experiments with animation and writing very primitive games in (you guessed it) Qbasic. So I pushed all of boilerplate into a base class in a library and now this one file can accomplish more just based on how the base class decides to run it; it’s pseudo-scripting. A great use of inversion-of-control in action 😊

And this same approach can be used to solve other problems too, depending on your style. Sometimes have situations where a class is dominated by one (or a few) very important methods that maintainers should focus on, particularly in derived types. Does this happen to you and if so, how do you highlight that? Do you just put a comment over it that says ' Keep this method at the top or do you put it in a separate partial file?

I really wanted to do something fun and not-console centric with this scenario. In my next scenario I’m going to expand on this approach to do something even cooler (and remote from Console apps) so look out!

Feedback welcome, please share, thanks!

Regards,

-ADG

P.S. Reminder: This is Scenario C. It’s the third of 5. I’ll post the usual GitHub issue with my writeup of all the design details/questions I ran into at a future date.