Roland Weigelt

Born to Code

  • WPF with Web API and SignalR – Why and How I Use It

    Preface: This blog post is less about going deep into the technical aspects of ASP.NET Core Web API and SignalR. Instead it’s a beginner’s story about why and how I started using ASP.NET Core. Maybe it contains bits of inspiration here and there for others in a similar situation.

    The why

    Years ago, I wrote a WPF application that manages media files, organizes them in playlists and displays the media on a second screen. Which is a bit of an understatement, because that “second screen” is in fact mapped onto the LED modules of a perimeter advertising system in a Basketball arena for 6000 people.

    Unfortunately, video playback in WPF has both performance and reliability problems, and a rewrite in UWP didn’t go as planned (as mentioned in previous blog posts). Experiments with HTML video playback, on the other hand, went really well.

    At this point, I decided against simply replacing the display part of the old application with a hosted browser control. Because my plans for the future (e.g. synchronizing the advertising system with other LED screens in the arena) already involved networking, I planned the new software to have three separate parts right from the beginning:

    1. A server process written in C#/ASP.NET Core for managing files and playlists. For quick results, I chose to do this as a command line program using Kestrel (with the option to move to a Windows service later).
    2. A (non-interactive) media playback display written in TypeScript/HTML, without any framework. By using a browser in kiosk mode, I didn’t have to write an actual “display application” – but I still have the option to do this at a later time.
    3. A C#/WPF application for creating and editing playlists, starting and stopping media playback, which I call the cockpit. I chose WPF because I had a lot of existing code and custom controls from the old application that I could reuse.

    The how: Communication between server, cockpit and display

    For communication, I use Web API and SignalR.

    Not having much prior experience, I started with the “Use ASP.NET Core SignalR with TypeScript and Webpack” sample and read the accompanying documentation. Then I added app.UseMvc() in Startup.Configure and services.AddMvc in Startup.ConfigureServices to enable Web API. I mention this detail because that was a positive surprise for me. When learning new technologies, I sometimes was in situations where I had created an example project A and struggled to incorporate parts of a separate example project B.

    For quick tests of the Web API controllers, PostMan turned out to be a valuable tool.

    Before working on “the real thing”, I read up on best practices on the web and tried to follow them to my best knowledge.

    Web API

    I use Web API to

    • create, read, update or delete (“CRUD”) lists of “things”
    • create, read, update or delete a single “thing”

    In my case, the “things” are both meta data (playlists, information about a media file, etc.) as well as the actual media files.

    Side note: I wrote about my experiences serving video files in my post “ASP.Net Core: Slow Start of File (Video) Download in Internet Explorer 11 and Edge”.

    SignalR

    While I use Web API to deal with “things”, I use SignalR for “actions”:

    • I want something to happen
    • I want to be notified when something happens.

    Currently the server distinguishes between “display” and “cockpit” roles for the communication. In the future, it’s likely I will have more than one “cockpit” (e.g. a “remote control” on a mobile device) – and more roles when the application grows beyond simple media playback only one display. Using the SignalR feature of groups, the clients of the server receive only those SignalR messages they are interested in as part of their role(s).

    Example

    When I select a video file in the “cockpit”, I want the “display” to preload the video. This means:

    • The cockpit tells the server via SignalR that a video file with a specific ID should be be preloaded in the display.
    • The server tells* the display (again, via SignalR) that the video file should be preloaded.
    • The display creates an HTML video tag and sets the source to a Web API URL that serves the media file.
    • When the video tag has been created and added to the browser DOM, the display tells the server to – in turn – tell the cockpit that a video with the specified is ready to be played.

    *) When I write “the server tells X”, this actually means that the server sends a message to all connections in group “X”.

    The cockpit

    In my WPF applications, I use the model-view-view model (MVVM) and the application service pattern.

    Using application services, view models can “do stuff” in an abstracted fashion. For example, when the code in a view model requires a confirmation from the user. In this case, I don’t want to open a WPF dialog box directly from a view model. Instead, my code tells a “user interaction service” to get a confirmation. The view model does not see the application service directly, only an interface. This means that the view model does not know (and does not care) whether the response really comes from a dialog shown to the user or some unit test code (that may just confirm everything).

    Application services can also offer events that view models can subscribe to, so the view models are notified when something interesting happens.

    Back to Web API and SignalR: I don’t let any view model use a SignalR connection or call a Web API URL directly. Instead I hide the communication completely behind the abstraction of an application service:

    • Web API calls and outgoing SignalR communication are encapsulated using async methods.
    • Incoming SignalR communication triggers events that view models (and other application services) can subscribe to.

    Minor pitfall: When a SignalR hub method is invoked and the handler is called in the WPF program, that code does not run on the UI thread. Getting around this threading issue (using the Post() method of SynchronizationContext.Current) is a good example of an implementation detail that an application service can encapsulate. The application service makes sure that the offered event is raised on the UI thread, and if a view model subscribes to this event, things “just work”.

  • Looking Back at 2018

    The end of the year is typically a time to look back – here’s my personal list of programs and technologies that played an important role for me in 2018.

    Visual Studio Code: It keeps getting better and better

    This editor-becoming-an-IDE needs no introduction. I have included it in this list because 2018 was the year where I started doing meaningful work beyond editing HTML/[S]CSS files in Visual Studio Code.

    For my purposes, it does not replace “classic” Visual Studio, but complements it. It’s not uncommon for me to debug ASP.NET Core and TypeScript code in Visual Studio Code as well as WPF code in Visual Studio 2018 at the same time (in a project where SignalR is used for Desktop Client <-> Server <-> Web Client communication).

    I’m extremely impressed by the ecosystem of extensions (e.g. Live Sass Compiler, Live Server) as well as the ongoing development with its monthly releases.

    Linea Sketch on iPad Pro: So good, it’s almost worth buying the hardware for

    I love Linea Sketch, which is an iPad app for (as the name implies) sketching. When I tried out various graphics applications for my 2018 iPad Pro, I was looking for something that would allow me to quickly draw UI sketches and illustrations for presentations without much overhead. Linea Sketch caught my attention because of the combination of simplicity and power. Two highlight features of the app are “ZipLine” and “ZipShape”, which let you quickly draw straight lines, circles and polygons without breaking your flow of work with the pen.

    Take a look at the Linea Sketch website to learn more about this fantastic app.

    UWP: I wanted to like it, but what a disappointment…

    I already wrote a bit about my frustration with the Universal Windows Platform (UWP) in the introduction to my previous blog post.

    Obviously, each new platform comes with a learning curve. If you have a clear vision of what you want to develop and are learning how to do it along the way, you are bound to take longer than expected. What happened with UWP, though, was that I encountered problems that too often became roadblocks for hours or sometimes days. If you get silent crashes or low-level exceptions with an HRESULT that basically says, “something went wrong”, the only thing you can do is to comment out code you have just written up to a point where the program is working again. That reminded me very much of the early Silverlight days (version 2 and 3), Back then, error messages only became helpful in later versions (I remember version 4 and 5 as being good enough).

    Web searches showed me that I wasn’t alone. Every so often, a question on a forum would made me go “yeah, I’d like to know an answer to that, too”. Unfortunately, often only reply would clearly indicate that the original post was only scanned for keywords, not actually read, let alone understood. Obviously, this is not a specific UWP problem. It’s just that other technologies seem to have reached a critical mass of users, so that e.g. on StackOverflow, additional comments and answers appear quicker and in larger numbers.

    The final straw for me were silent crashes of the Windows App Cert Kit, which had worked on my machine earlier. Searching for a solution, I came across Microsoft forum threads reporting WACK problems that went on for months, with no real solution in sight.

    I don’t know whether the WACK problem has been solved now, or whether UWP in general has become friendlier in terms of developer experience. But frankly, I have stopped caring. After all, we’re talking about programming as a hobby. Maybe I’ll revisit UWP in a few years – but for now, I have moved on.

    And by the way: I actually do like UWP APIs. They make e.g. creating a thumbnail of a media file or determining the length of a video file super-easy. But I can use these APIs from a WPF program as well, so that’s exactly what I’m doing now.

    ASP.NET Core (Web API, SignalR): A positive surprise

    While working with UWP was hard work for every step along the path, ASP.NET Core was clearly the opposite experience for me. Whenever I ran into a problem, I found a sample or some forum or StackOverflow post that helped me find a solution. And unlike with UWP, where I came from a WPF and Silverlight background, I didn’t have much prior knowledge.

    To put things in perspective:

    • I started with version 2.1, i.e. I surely skipped a lot of the problems of the 1.x days.
    • I found a great starting point with the SignalR with TypeScript and WebPack sample.
    • I use ASP.NET for non-UI, server-related functionality that is limited in scope.

    So, your mileage may vary. For me, the positive initial experience was a great motivation to learn more about the platform and to overcome the small problems that are simply a natural part of software development.

  • How to Make Chrome Kiosk Mode “just Work”

    There’s a reason why I haven’t blogged about UWP lately: The overall development experience (slow turnaround cycles, silent crashes, HRESULTs instead of error messages, you name it) drove me mad up to the point I scrapped my whole project, a digital signage solution, in early summer. Instead, I now use Chrome as my “render engine” and things are working pretty well. Without prior experience in using ASP.Net Core, WebAPI and SignalR, I have been able to whip something up to be ready for the 2018/19 Basketball season.

    During development, I had to figure out

    1. how to use Chrome without any… chrome (i.e. no title, adress or tool bars),
    2. how to move the Chrome window to the secondary screen,
    3. how to close Chrome from code and
    4. how to still be able to use Chrome for browsing during development.

    tl;dr: On https://github.com/RWeigelt/ChromeKioskModeDemo you find a small demo project (C#/WinForms for simplicity) that’s pretty self-explanatory.

    Problems #1 and #2 are easy: Chrome has a so-called kiosk mode (command line parameter --kiosk http://www.example.com) that will display the specified web page in full-screen mode. Another command line parameter deals with with positioning (--window-position=top,left). In the demo code you’ll see other parameters, they force the window size for a cleaner startup.

    Problems #3 and #4 turned out to be connected to each other.

    One might wonder what’s so hard about closing Chrome from code. Don’t you just start a process with Process.Start and remember the returned Process instance, to later call its CloseMainWindow method? What could possibly go wrong?

    Well, for starters, that Process instance may live shorter than expected. If you have a couple of Chrome windows and/or tabs open, Chrome will do a lot of process management behind the scenes – and “your” process may not be the one displaying the requested web page.

    On the other hand, if you go from zero Chrome windows to one window with a single tab, things are nice and easy. Now while you could force yourself to use a different browser during development, you never now whether there isn’t some Chrome window open later in production.

    Fortunately, if you specify a different “user data directory” (--user-data-dir=directory) when starting Chrome, you can achieve this “one window, one tab, one process” scenario even if you have many windows and tabs open.

    For details, take a look at the code on https://github.com/RWeigelt/ChromeKioskModeDemo. This C#/WinForms project shows a form with two buttons:

    • “Open Chrome” will open http://www.example.com in full-screen mode on the second monitor (sorry, you have to have a second monitor for the demo).
    • “Close Chrome” closes the Chrome window without affecting any other Chrome windows.

    Note that this is not a library, just some code I have taken from my solution (stripped down for clarity). You’ll want to adapt it to your needs anyway. Have fun with it!

  • Emaroo 4.3 – Support for Adobe CC 2019 / VS Code 1.28

    Emaroo is a free utility for browsing most recently used (MRU) file lists of programs like Visual Studio, VS Code, Word, Excel, PowerPoint, Photoshop, Illustrator and more. Quickly open files, jump to their folder in Windows Explorer, copy them (and their path) to the clipboard - or run your own tools on files and folders with custom actions!

    About this Release

    • Added: Support for Photoshop/Illustrator/InDesign CC 2019.
    • Updated: Support for Visual Studio Code 1.28 (changes regarding of most recently used files). Previous versions of Visual Studio Code are still supported.
    • Changed: Emaroo no longer looks for Photoshop/Illustrator CC versions prior to 2018 by default. This does not affect support for CS6 versions (which some users keep for compatibility reasons).

      If you still need support for older CC versions, you can enable it as follows:

      • Close Emaroo
      • Start Notepad as Administrator
      • Open the file Emaroo.exe.config in the installation directory (usually C:\Program Files (x86)\Weigelt\Emaroo)
      • Set SearchForOldAdobeCCApplications option to True
      • Save the config file and start Emaroo.
  • Design/UI/UX-Praxiswissen im Dezember in Berlin

    Am 11. Dezember halte ich im Rahmen der GUI&DESIGN 2018 den Workshop “Von Null auf GUI - Design/UI/UX-Praxiswissen für Entwickler”. Auf der Hauptkonferenz (12./13. Dezember) folgt dann mein Vortrag “Kochrezepte für die Gestaltung von GUIs”.

    Ich freue mich schon sehr auf die Konferenz!

    Zum einen, weil der Workshop und der Vortrag viel Spaß machen und das Feedback danach immer sehr positiv ist – mein Stil aus “praxisorientierter Abstraktion” scheint gut anzukommen. Bei der Developer Week in Nürnberg hatte ich den Vortrag vor dem Workshop-Tag gehalten und plötzlich saßen im Workshop drei zusätzliche Teilnehmer, die ihre ursprüngliche Workshop-Buchung kurzfristig über den Haufen geworfen hatten.

    Zum anderen, weil ich tatsächlich mal die Konferenz komplett genießen kann, denn dieses Jahr hat es zeitlich gepasst. Das Programm ist noch nicht vollständig, aber die Vorträge, die bereits online sind, klingen sehr vielversprechend.

    Alle Infos zu Konferenz: https://gui-design.ppedv.de/18

  • Emaroo 4.2.1 – Bugfix for VS Code Workspaces

    Emaroo is a free utility for browsing most recently used (MRU) file lists of programs like Visual Studio, VS Code, Word, Excel, PowerPoint, Photoshop, Illustrator and more. Quickly open files, jump to their folder in Windows Explorer, copy them (and their path) to the clipboard - or run your own tools on files and folders with custom actions!

    About this Release

    This is a small bugfix release that addresses a problem with Visual Studio Code workspaces.

    Thanks to Jochen Manns for reporting the issue and providing repro information that helped fixing the bug.

  • Emaroo 4.2 – Update for Visual Studio Code 1.26

    Emaroo is a free utility for browsing most recently used (MRU) file lists of programs like Visual Studio, VS Code, Word, Excel, PowerPoint, Photoshop, Illustrator and more. Quickly open files, jump to their folder in Windows Explorer, copy them (and their path) to the clipboard - or run your own tools on files and folders with custom actions!

    • Download Emaroo on www.roland-weigelt.de/emaroo
    • Get ready-to-use custom actions on GitHub, e.g.
      • Open a Visual Studio project/solution in a specific version of Visual Studio
      • Open the Visual Studio developer command line
      • Open a file or folder in Visual Studio Code
      • Open a folder in Git Bash or Git GUI
      • Attach a file to a new email in Outlook
    • Learn how to write your own custom actions in a quick step-by-step guide.

    About this Release

    The recent release of Visual Studio Code 1.26 brought a couple of changes that made it disappear from Emaroo. With VS Code being one of the tools and applications that I constantly launch from Emaroo, that is obviously a bad thing.

    Fortunately I had a more or less finished version 4.2 that was just waiting for an important reason for a release.

    Other release notes:

    • Changed: The settings for Show hidden and Show missing now work across tabs and are persisted when exiting Emaroo.
    • Improved: Reduced flicker when changing tabs.
    • Fixed: On some systems a black line appeared at the bottom of the VS2017 tab.
    • Workaround: In case the MRU list for Visual Studio 2017 shows only old items (or none at all), you can now switch the strategy how the MRU items are determined. See the ReadMe in the ZIP file for more information.

    A big Thank you! to Darren Schroeder for his support (technical info, example code, testing).

  • ASP.Net Core: Slow Start of File (Video) Download in Internet Explorer 11 and Edge

    While experimenting with the <video> tag on an HTML page with a web API endpoint as the source (ASP.NET Core 2.1.1), I noticed that the (not auto-playing) videos

    • appeared immediately in Chrome and Firefox,
    • but took a few seconds in Internet Explorer and Edge to show up on the page.

    This is what the code in my controller looked like:

    [HttpGet("{id}")] // api/video/example
    public IActionResult GetVideoByName(string id)
    {
    	// ...
    
    	var path = Path.Combine(@"D:\Example\Videos", id + ".mp4");
    	return File(System.IO.File.OpenRead(path), "video/mp4");
    }

    Searching the web for the obvious keywords (IE11, ASP.NET Core, file, stream, slow, download, etc.) yielded lots of results for all kinds of problems. In the end I found out that I needed to enable something called “range processing” (pardon my ignorance, I’m more of a UI guy than a networking expert).

    Fortunately, ASP.NET Core 2.1 offers a (new) overload for the File() function with a boolean parameter aptly named enabledRangeProcessing. So the solution is to set that parameter to true:

    	return File(System.IO.File.OpenRead(path), "video/mp4", true);
    
  • Emaroo 4.1 – Hide Those Tryout Visual Studio Projects!

    Emaroo is a free utility for browsing most recently used (MRU) file lists of programs like Visual Studio, VS Code, Word, Excel, PowerPoint, Photoshop, Illustrator and more. Quickly open files, jump to their folder in Windows Explorer, copy them (and their path) to the clipboard - or run your own tools on files and folders with custom actions!
     

    • Download Emaroo on www.roland-weigelt.de/emaroo
    • Get ready-to-use custom actions on GitHub, e.g.
      • Open a Visual Studio project/solution in a specific version of Visual Studio
      • Open the Visual Studio developer command line
      • Open a file or folder in Visual Studio Code
      • Open a folder in Git Bash or Git GUI
      • Attach a file to a new email in Outlook
    • Learn how to write your own custom actions in a quick step-by-step guide.

    About this Release

    With Emaroo 4.1, you can now hide files or directories This is nice for hiding all those small tryout projects (“App1”, “App2”, etc.) that you are just not quite ready yet to delete on disk.

    Open the context menu and check the “Hide in list” option:

    20180705_HideInList

    To make a hidden list item visible again, check the “Show hidden” checkbox (to show all hidden items)…

    20180705_ShowHidden

    …and open the context menu on the item you want to show again.

    Then uncheck the “Hide in list” option:

    20180705_ShowAgain


    The release also fixes a couple of bugs, so an update is definitely recommended!

    Read the full release notes on the Emaroo website.

  • Emaroo 4 – Custom Actions on Overdrive!

    Emaroo is a free utility for browsing most recently used (MRU) file lists of programs like Visual Studio, VS Code, Word, Excel, PowerPoint, Photoshop, Illustrator and more. Quickly open files, jump to their folder in Windows Explorer, copy them (and their path) to the clipboard - or run your own tools on files and folders with custom actions!
     

    • Download Emaroo on www.roland-weigelt.de/emaroo
    • Get ready-to-use custom actions on GitHub, e.g.
      • Open a Visual Studio project/solution in a specific version of Visual Studio
      • Open the Visual Studio developer command line
      • Open a file or folder in Visual Studio Code
      • Open a folder in Git Bash or Git GUI
      • Attach a file to a new email in Outlook
    • Learn how to write your own custom actions in a quick step-by-step guide.

    About this Release

    Version 4 of Emaroo is here, with major improvements for custom actions:

    • New dialog for editing custom actions.
    • New debug dialog for previewing how text macros are expanded before executing a custom action.
    • New clipboard format for quickly sharing custom actions.
    • New macros for more portable custom actions.
    • Tooltips for your custom actions.

    Read the full release notes on the Emaroo website.

    The New Clipboard Format for Sharing Custom Actions

    When you copy a custom action on the settings tab…

    20180614_SettingsTab

    …Emaroo places a text on the clipboard that looks something like this:

    §§!F5[*J,l;DzzK6yn}|N|U1op[BMW+uMsNa5QD-fRa#}~TEgEV^I7O#-1^kHDi;°(*VI|84#6XX*4%b
    E{4A(+*Na;s,sUYLqQCjdDvmGd6aQ0oQ4Mek-|cHCVcXi:Z]BHkuh5|nt°3A]dkKiNMO-*{}apX+T=y^
    10ETC°i5lL^Qcm~jSi,kSgax1Xhv*§§

    You can then paste the custom action into a mail or chat window, post it on your website, Facebook etc. to share it with others.

    The text format does not use characters that have to be escaped e.g. when inserting the text into HTML. You can also add or remove spaces or linebreaks as long as you keep the “§§” at the start and the end.

    File-based Sharing of Custom Actions

    Emaroo still does (and will continue to) support import from/export to JSON files (“*.action.json”) for version control and backup purposes – it’s always good to have the source Winking smile.