Recently, I have written a series of articles on modernizing ASP.NET Web Forms apps. Now this topic became even more important thanks to the recent announcement of .NET 5. It was made clear that ASP.NET Web Forms will not be ported to .NET Core.

TLDR: DotVVM can run side by side with ASP.NET Web Forms, and it also supports .NET core. You can install it in your Web Forms project and start rewriting individual pages from Web Forms to DotVVM (similar syntax and controls with MVVM approach) while still being able to add new features or deploy the app to the server. After all the Web Forms code is gone, you can just switch the project to .NET Core. See the sample repo.

To rewrite or continuously upgrade

There are still plenty of ASP.NET Web Forms applications out in the world and their authors now stand by a difficult decision:

  • Throwing the old application away and rewrite it from scratch using modern stack
  • Trying to continously modernize the app and rewrite all the pages on-the-fly

The first option – total rewrite – is very time consuming. If the original application was developed for more 10 years, which is not uncommon, I can hardly imagine that it can be rewritten it in less than half of that time. In addition, when the application needs to support company daily tasks and workflows while responding to rapidly changing business needs, it is impossible to stop adding new features for months or even years because of the rewrite.

Of course, the company can build a new team that will develop the new version while keeping the old team maintaining and extending the old app, but it means double effort and a vast amount of time required to transfer the domain knowledge from the old team to the new one. Also, many things will need to be done twice, and it will probably take years until the new version is ready for production.

And finally, the management never likes to hear about rewriting the software from scratch. I have seen many situations where the project leads had to fight very hard in order to justify such decision.

The second option – the continuos modernization – looks a little bit easier. Imagine you have a Web Forms application with hundreds of ASPX pages. If you can rewrite one page per day using other technology and integrate the new pages with the old ones so the user won’t notice they are made with different stacks, after several months you can get rid of all of the ASPX pages and stay with a more modern solution. It may not be perfect as there will still be some legacy code, but it is much better than nothing, and if you are lucky and don’t use WCF or Workflow Foundation which are also not supported on .NET Core, you will be able to move the project to .NET Core.

Two projects? Possible, but maybe more difficult than it has to be.

But how to do it? Let’s suppose we have an old app that needs to be maintained.

Shall we create a new ASP.NET Core project that would run side by side, maybe on the same domain, and make links from the old to new pages and vice versa?

It can work if the same CSS styles are used. The user should not be able to tell that he actually uses two web apps.

However, there may be some issues with sign-on as the new app can use different authentication cookies than the old one – the authentication will need to be integrated somehow. Also, if session is used (which is not a good idea in general, but it is also quite frequent), it will not be shared between the two applications.

Moreover, this will require some configuration changes on the server, and the deployment model will need to be changed as you will now deploy two applications instead of one.

If the application caches some data in memory, you may also run into various concurrency issues as the caches will need to be invalidated. There will also be some duplication if the business layer is not properly separated from the UI.

What is more, if you decide to use Angular, React or other JavaScript framework, there is also a large amount of knowledge required to start working with these technologies. The business logic and data will have to be exposed through a REST API (or Graph QL), which may be an additional effort to set up at the beginning.

DotVVM can make this simpler

What if there is a framework that can be run side by side with ASP.NET Web Forms in one application, but works also with the newest versions of ASP.NET Core?

It would make so many things easier. You will have just one project to deploy. There will be no changes in the deployment model – it will still be an ASP.NET application. You won’t need to take care about sharing the user identity between two apps because there won’t be two apps.

With DotVVM, it is quite easy. It was one of our initial thoughts that lead us to start with the project. If you haven’t heard of it – it is an open source MVVM framework supporting both ASP.NET and ASP.NET Core. It has nice Visual Studio integration and recently joined the .NET Foundation.

How does the migration work?

You can install DotVVM NuGet package in the Web Forms application and it will run side by side with the ASPX pages that are in the project.

From the deployment perspective, there are no changes – it is still the same ASP.NET application that gets deployed to the server as usual.

You can start with copying the Web Forms master page and converting it in the DotVVM syntax. It is different, but not much – most of the controls have the same names, except that you are using the MVVM approach. Use the same CSS so the users won’t notice the change.

Then, you can start rewriting all the pages one by one from Web Forms to DotVVM. DotVVM contains similar controls like GridView, Repeater, FileUpload and more. The most difficult part will be extracting the business logic from the ASPX code behind to the DotVVM viewmodel, but it is still C#.

If your business layer was propely separated, it should be trivial. If not, take this as an opportunity to do the refactoring and get the cleaner code. Thanks to the MVVM approach, your viewmodels will be testable and the overall quality of the application will greatly improve.

DotVVM pages will share the environment with the ASP.NET ones, including the current user identity. You won’t need to expose your business logic through a REST API, you can keep the same code interacting with the database.

At each point of the process, the application works, can be extended with new features, and can be deployed. The team is not locked to the migration and can do other things simultaneously.

After a few months, when all the ASPX pages are rewritten in DotVVM, you will be able to create a new ASP.NET Core project, move all DotVVM pages and viewmodels into it and use them with .NET Core. The syntax of DotVVM is the same on both platforms.

If you have been using Forms Authentication in Web Forms, you will need to switch it to ASP.NET Core Cookies, but that should be an easy-enough change.

Are there any samples?

Yes, I have created a GitHub repo which describes the process in detail. There are five branches, each one displaying one of the steps.

In the first one, there is a simple ASP.NET Web Forms application. In the last one, there is the same app rewritten in DotVVM and running on .NET Core.

We have used this way to migrate several Web Forms applications. If the business layer is separated properly, rewrite on one page takes about 1 hour in average. If the business logic is tighen up with the UI, it can take significantly more time, but it can be a way to improving the application testability and I think it is worth – even poorly written apps can be saved using this way.

What if I need help?

We’ll be happy to help you. You can also contact the DotVVM team on our Gitter chat. Check out the DotVVM documentation and the cheat-sheet of differences between Web Forms and DotVVM.

Recently, I have been doing a few live streams with Michal Altair Valasek, fellow MVP from the Czech Republic. We took his AskMe demo app which shows how to build a non-trivial web app in ASP.NET Core, and made a version built in DotVVM.

These streams were in Czech language, but I got some requests to make live streams in English. So this time, I will be streaming in English, and I will try to fix some issues in DotVVM and bring a few new features in the framework.

The stream will be on my personal Twitch on Thursday 4/4/2019 at 7:30 PM CEST.

Watch TomasHerceg's live video on

It has been a long time since I discovered this nice Reddit thread about Metric vs Imperial system. There was an amazing comment listing all kinds of ounces, barrels, gallons and other crazy stuff, but recently it got deleted.

Thanks to Removeddit, a site that keeps deleted Reddit comments, I succeeded in recovering it. I believe there was a reason for deleting the comment by its author, and I hope that the author of this brilliant text wouldn’t mind - I just have to post it here so I can read it and laugh again and again:

There are four different ounces in use:

  • A Troy ounce is about 31.1 grams.

  • An Avoirdupois ounce is about 28.3 grams.

  • An Imperial fluid ounce is about 28.4 ml.

  • A US fluid ounce is about 29.57 ml.

This is related to the fact that a US fluid ounce is 1/16 of a US pint, while an Imperial fluid ounce is 1/20 of an Imperial pint, and an Imperial pint and a US pint are different. There are in fact three pints:

  • An imperial pint about is 568 ml, or 20 Imperial fluid ounces.

  • A US pint is about 473 ml, or 16 US fluid ounces.

  • A dry pint is about 551 ml, or XXX dry fluid ounces... no, wait a "dry fluid ounce" doesn't exist, I wonder why.

This is in turn related to the fact that there are three gallons:

  • The Imperial gallon is defined in metric terms as exactly 4.54609 litres. It contains 8 Imperial pints.

  • The US gallon is defined as 231 cubic inches. It contains 8 US pints.

  • The dry gallon is defined as 1/8 of a US bushel. It contains 8 dry pints.

However, there are only two types of bushels:

  • The imperial bushel, equal to 8 imperial gallons.

  • The US dry bushel, equal to 8 US dry gallons.

There is no such thing as a US (non-dry) bushel, so if you want to convert a US gallon into the next higher US unit of volume, you have to use the beautiful correspondence:

  • 1 US bushel = 9.30918 US gallons

The next higher up unit for measuring units is the barrel (thanks /u/AML86 for the reminder). There are at least ten different units called a barrel. Among these we will mention:

  • A dry barrel is 7056 cubic inches, which converts to a convenient ~3.28 dry bushels.

  • A barrel for cranberries (yes, really) is 5826 cubic inches , more or less ~2.71 bushels.

  • An Oil barrel is 42 US gallons.

I have been speaking at various conferences and events for more than 10 years. Over the years, I tried several ways of recording my sessions. Most of the ways were just OK, but they were not 100% reliable, and it always bothered me when I did a conference with amazing sessions and some of them fail to record.

Recently, I have built my custom device that can do the entire recording or live-streaming job done without interfering with anything I want to present, and can be used on conferences where devices are changed frequently and each has a completely different setup.

But first, let me briefly list the ways I have been using, and point out their pros and cons.


Camtasia is probably the best software for screen recording. It comes with a simple editor where you can do basic processing of the video, and export it to common formats.

I was using Camtasia for a couple of years succesfully, however there are some things you’ll want to change in Camtasia settings, otherwise your recording can be easily ruined:

  1. The default keyboard shortcuts in Camtasia collide with some shortcuts in Visual Studio. For example, when you debug something during your presentation and press F10, Camtasia will stop the recording. If you don’t notice that, you have just lost the rest of your session.
  2. Camtasia stores the recordings to you C drive by default. If you have multiple drives (C for system and D for data), you may want to put it to some other location so you won’t run out of disk space. It is a good idea to place Camtasia temp folder to a USB stick (USB 3.0) so you’ll get full performance from your drive for your Visual Studio builds, virtualization or any other stuff you use in your presentation.
  3. Double-test your microphone settings so you don’t lose your audio. Recording the sound on a separate backup device is always a good idea. On some PCs, I have not been successful in recording the sound from Camtasia at all – sometimes I have been hitting various driver issues, or there was a problem when two audio devices on the PC used the same name.

The main issue with Camtasia is that it drains the performance of your machine while you are presenting. It is not a problem if you only have PowerPoint slides, but if you need to use Visual Studio, Docker and other stuff during the session, your machine will be much slower than without recording. Two or three times, my laptop got overheated and just turned off in the middle of my presentation. The recording was of course lost completely as the temp file was corrupt.

If you organize a conference and want to use Camtasia, you will need to convince all speakers to install it, and I totally understand the speakers who won’t do it. It is always risky to install anything before the presentation, especially when you don’t know the software. It can interfere with the things you want to show, and finally, there is never enough time to do it before the presentation and test it properly – everyone wants to focus on the session and not spend time by installing something. 

AverMedia Frame Grabbers

Over the years, I have also tried several frame grabbers from AverMedia, namely AverMedia ExtremeCap 910 and AverMedia Game Capture HD II.

The first one can record VGA or HDMI on a SD card, the second one records HDMI on its internal hard drive. Be careful about the SD card you want to plug in – not all SD cards worked for me.

The advantage is that your device is not affected by the recording at all, and it is simple to use – just plug the frame grabber between your laptop and projector.

On the other hand, there are several problems with this approach:

  1. You don’t know if the recording succeeded unless the presentation ends, and you check what has been recorded. Sometimes you’ll find an empty file, a hour-long video of entirely black screen, or just a part of the session.
  2. When the speaker changes the screen resolution during the presentation, or switches from Duplicate mode to Extend, the recording won’t probably survive this and ends or produce a corrupted file.
  3. The quality of audio recorded by the frame grabbers is terrible. You need a separate audio recording device, or a good external microphone that will be connected to the grabber.
  4. You’ll need to do post processing as the grabbers often don’t produce a video in a format which is suitable for direct upload.

All in all, this method failed me many times. I hardly remember a conference when 100% of recordings succeeded using this method.

On the other hand, my colleagues from Windows User Group are using this way for years and have successfully recorded hundreds of sessions.

My Custom Device

Few years ago, one of my colleagues was doing some live streams with OBS, and that inspired me to build my own device for recording or streaming.

Of course, I could install OBS directly on my laptop, but that wouldn’t work on conferences which I organize (convincing the speakers to install and configure OBS on their machines).

Instead, I built my device from the following parts:

  • Intel Nuc that runs Windows 10 and OBS. I got the version with Core i5 processor and put there 256GB SSD drive so I have enough space for the recordings.
  • Elgato Game Capture HD60 that can grab HDMI signal and behaves like a USB 3.0 webcam.
  • Zoom H1N for recording the sound. It is a good-quality dictaphone that can record audion on a micro-SD card, or behave like a USB microphone (that’s what I need).
  • Logitech C922 Pro Stream USB webcam to record the speaker.
  • Asus VT168H 15.6’’ LCD touch screen.

I have mounted the Intel Nuc on the back of the LCD display. Thanks to the fact that it is a touch screen, I don’t need mouse and keyboard connected.

I can then just connect the webcam, the grabber and the Zoom recorder in the USB ports (there is enough of them) and use OBS to record or stream.

I have tested the Elgato grabber that it survives when the screen resolution changes or Duplicate mode switches to Extend and vice versa. It survives even disconnecting and re-connection of any device, and I can always check what's being recorded or streamed in real-time thanks to the display.

The entire setup costs about $900, but it is the most reliable and flexible solution I have found so far.

Elgato grabber

Logitech webcam

Zoom recorder

Intel Nuc mounted on the LCD

Since the webcam can be placed few meters away from the speaker’s post, I also recommend connecting it using an active USB 3.0 extension cable.

Here is a photo of my studio I have built in our offices. It is ready for the speaker to just sit down, plug the HDMI cable in their laptop, and start presenting.



The software

As I already mentioned, I am using OBS. It is an awesome open source project, and it proved to be very reliable.

You can define as many scenes as you want, and add any kinds of video or audio sources in every scene.

I have three scenes – just the screen, just the speaker or a combined view (I am using it most often). Also, for the live streams, I have a static scene for intro, intermission and outro.

OBS with Camera Only scene

OBS with Combo scene

You can switch between the scenes using the touch screen. One of my friends is building a simple device with several buttons to switch the scenes and start/stop recording – it will be more accurate than the touch screen.

For streaming, you just need to enter the stream key in the Settings of OBS. OBS supports many streaming services. I stream on Twitch and then export the videos to YouTube (I often edit them a little bit).

When I just record, the videos are stored on the internal SSD drive I put in the Intel Nuc.


The videos recorded in OBS comes in FLV format. It can be changed, the reason for FLV is a support for missed frames which can happen, especially in streaming scenarios.

I use Adobe Premiere to edit my recordings, which doesn’t support FLV, but it is simple to convert FLV into MP4 using ffmpeg.

ffmpeg -i myvideo.flv -codec copy myvideo.mp4

The conversion is very quick and it is loseless – the stream itself is not affected, only the container is changed from FLV to MP4.


We have recently started coding live with my friend Michal Altair Valasek, and had a great fun. This device helped us to do the stream right away without spending much time to prepare it, and I have used the device to record the sessions on our latest conference. We had some issues and one of the sessions failed to record because of a human error, but next time we’ll be more careful.

I believe that I have finally found a reliable and still affordable way to record or stream sessions from conferences I organize.

Yesterday, we got a question from one of DotVVM customers. He was using the Business Pack GridView with the inline editing feature and asked us how to allow the user to save changes in the row by pressing Enter.

Default button in forms

DotVVM itself doesn’t include any specific functionality to handle the keyboard actions – we rely on default behavior in HTML.

The situation is quite easy to solve when you create a simple form – to make the button to respond to the Enter key, you need to make it a “submit” button, and it needs to be in a <form> element.

        <label>User Name</label>
        <dot:TextBox Text="{value: UserName}" />
        <dot:TextBox Text="{value: Password}" Type="Password" />

        <dot:Button Text="Sign In" Click="{command: SignIn()}"
                    IsSubmitButton="true" />

The only thing you need to do is to set IsSubmitButton to true so the button will add type=”submit”. And of course, the form fields and the button must be inside the <form> element.

Modal dialogs and GridView inline editing

A little bit interesting situation occurs in modal dialogs and GridView control where you want to allow the users to edit a single row and save the changes on Enter.

The ModalDialog control has the ContentTemplate and FooterTemplate child elements, so you will have the form fields in one template and the save button in the other. You would need to put the entire modal dialog in a <form> element to make it work, and since forms in HTML cannot be nested, it might be an issue if you have more complicated scenarios.

Using the default button while editing data in GridView is completely impossible to do because the table row is <tr> and you cannot place <form> inside. You would have to put the entire table in the <form> element which is not nice and there might be multiple submit buttons if you want to allow the user to edit any row.

Moreover, there is no standard way to react to the Escape key if the user wants to cancel the edit. 

Extending DotVVM

It might be easy enough to google for a piece of jQuery code which will find the <input> elements in the form, catch the Enter press and click the correct button.

However, it is not difficult to write a generic solution for this problem and make it reusable. Basically, we need to define a container in which the Enter and Escape keys will be redirected to a particular “default” or “cancel” button. Something like the <form> element does, but even if it’s not the <form>.

In DotVVM, you can declare attached properties that can be added to any HTML element or DotVVM control. It is the same concept as attached properties in WPF or other XAML-based frameworks.

The attached property in DotVVM can render additional HTML attributes or Knockout data-bindings to the element or control on which it is applied.

What I want to achieve is something like this:

<tr data-bind="dotvvm-formhelpers-defaultbuttoncontainer: true">
        <dot:Button Text="Save" ...
                    data-dotvvm-formhelpers-defaultbutton="true" />
        <dot:Button Text="Cancel" ... 
                    data-dotvvm-formhelpers-cancelbutton="true" />

The <tr> element specifies my custom Knockout binding handler which catches all Enter and Escape key presses from its children. If the Enter is pressed inside the <tr> element, this handler will find the control marked with data-dotvvm-formhelpers-defaultbutton attribute and clicks on it. A similar thing will be done for the Escape key, only the data attribute is different.

I didn’t want to use the button IDs of as there will be multiple rows in the grid and I would need to generate unique IDs for the buttons. Marking the control with the data attribute looks nicer to me.

I am setting all attributes and binding handlers to true. Actually, their values are not important at all because they are not used, but I needed something to be there. 

The binding handler should also stop the propagation of the event because the grid may be in a modal dialog which might want to use this concept too and we don’t want to submit two things with one press of Enter.

So first, let’s declare the attached properties so we can use them in DotVVM markup:

public class FormHelpers
    [MarkupOptions(AllowBinding = false)]
    public static readonly DotvvmProperty DefaultButtonContainerProperty
        = DelegateActionProperty<bool>.Register<FormHelpers>("DefaultButtonContainer", AddDefaultButtonContainer);

    [MarkupOptions(AllowBinding = false)]
    public static readonly DotvvmProperty IsDefaultButtonProperty
        = DelegateActionProperty<bool>.Register<FormHelpers>("IsDefaultButton", AddIsDefaultButton);

    [MarkupOptions(AllowBinding = false)]
    public static readonly DotvvmProperty IsCancelButtonProperty
        = DelegateActionProperty<bool>.Register<FormHelpers>("IsCancelButton", AddIsCancelButton);

    private static void AddDefaultButtonContainer(IHtmlWriter writer, IDotvvmRequestContext context, DotvvmProperty property, DotvvmControl control)
        writer.AddKnockoutDataBind("dotvvm-formhelpers-defaultbuttoncontainer", "true");

    private static void AddIsDefaultButton(IHtmlWriter writer, IDotvvmRequestContext context, DotvvmProperty property, DotvvmControl control)
        writer.AddAttribute("data-dotvvm-formhelpers-defaultbutton", "true");

    private static void AddIsCancelButton(IHtmlWriter writer, IDotvvmRequestContext context, DotvvmProperty property, DotvvmControl control)
        writer.AddAttribute("data-dotvvm-formhelpers-cancelbutton", "true");

As you can see, I have added the FormHelpers class in the project. It contains three attached properties:

  • DefaultButtonContainer is used to mark the element in which the keys should be handled.
  • IsDefaultButton is used to mark the default button inside the container – it will respond to the Enter key.
  • IsCancelButton is used to mark the cancel button inside the container – it will respond to the Escape key.

The DelegateActionProperty.Register allows to create a DotVVM property that calls a method before the element is rendered. This is the right place for us to render the Knockout data-bind expression for the first property, and the data attributes for the other properties.

Notice that the class is marked with the ContainsDotvvmProperties attribute. This is necessary for DotVVM to be able to discover these properties when the application starts.

The binding handler

All the magic happens inside the Knockout binding handler. It is a very powerful tool for extensibility and if you learn how to create your own binding handlers, you’ll get to the next level of interactivity. And thanks to DotVVM and its concept of resources and controls, it is very easy to bundle these binding handlers in a DLL and reuse them in multiple projects.

ko.bindingHandlers["dotvvm-formhelpers-defaultbuttoncontainer"] = {
    init: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
        $(element).keyup(function (e) {
            var buttons = [];
            if (e.which === 13) {
                buttons = $(element).find("*[data-dotvvm-formhelpers-defaultbutton=true]");
            } else if (e.which === 27) {
                buttons = $(element).find("*[data-dotvvm-formhelpers-cancelbutton=true]");

            if (buttons.length > 0) {
    update: function (element, valueAccessor, allBindings, viewModel, bindingContext) {

The binding handler is just an object with init and update functions. The init is called whenever an element with data-bind=”dotvvm-formhelpers-defaultbuttoncontainer: …” appears in the page. It doesn’t matter if the element is there from the beginning or if it appears later (for example when a new row is added to the Grid). It is called in all these cases.

The update function is called whenever the value of the expression in the data-bind attribute changes. Since we always have true here, we don’t need anything in the update function.

As you can see, I just subscribed to the keyup event on the element which gets this binding handler. This event bubbles from the control which received the key press to the root of the document. If the key code is 13 (Enter) or 27 (Escape), I look for the button with the correct data attribute.

If there is such a button (or possibly more of them), I click on it and stop propagation of the event.

I need to call blur before clicking the button because when the user changes the value of a text field, it is written in the viewmodel when the control loses focus. I need to trigger this event manually before the click event is triggered on the button. Otherwise, the new value wouldn’t be stored in the viewmodel at the right time.

The last thing is to register this script file so DotVVM knows about it. Place this code in DotvvmStartup.cs:

config.Resources.Register("FormHelpers", new ScriptResource()
    Location = new UrlResourceLocation("~/FormHelpers.js"),
    Dependencies = new [] { "knockout", "jquery" }

We also must make sure that the script is present in the page where we use the attached properties. The easiest way is to add the following control in the page (or in the master page if you use this often).

<dot:RequiredResource Name="FormHelpers" />

Currently, we don’t have any mechanism to tell the property to request this resource automatically, so you need to include the resource manually.

Using the attached properties

Now the markup can look like this:

<tr FormHelpers.DefaultButtonContainer>
        <dot:Button Text="Save" ...
                    FormHelpers.IsDefaultButton />
        <dot:Button Text="Cancel" ... 
                    FormHelpers.IsCancelButton />

The nice thing about the true values of these properties is that you don’t need to write =”true” in the markup, you can just specify the property name.

But wait, how do I apply the attached property to the GridView table row? The <tr> element is rendered by the control itself, it is not in my code.

Luckily, there is the RowDecorators property which allows to “decorate” the <tr> element rendered by the control. And there is also EditRowDecorators which is used for the rows which are in the inline editing mode.

<bp:GridView DataSource="{value: Countries}" InlineEditing="true">
        <bp:GridViewTextColumn ValueBinding="{value: Id}" HeaderText="ID" IsEditable="false" />
        <bp:GridViewTextColumn ValueBinding="{value: Name}" HeaderText="Name" />
                <dot:Button Text="Edit" Click="{command: _root.Edit(_this)}" />
                <dot:Button Text="Save" Click="{command: _root.Save(_this)}" FormHelpers.IsDefaultButton />
                <dot:Button Text="Cancel" Click="{command: _root.CancelEdit(_this)}" FormHelpers.IsCancelButton />
        <dot:Decorator FormHelpers.DefaultButtonContainer />

As you can see, I have used <dot:Decorator> to apply the FormHelpers.DefaultButtonContainer property to the rows.

The buttons are rendered in the EditTemplate and I have just applied the properties to them.

GridView with inline edit mode

Now the user can change the value and use Enter and Escape keys to click Save or Cancel button.


Knockout binding handlers are very powerful and can help to improve the user experience. In fact, most of the DotVVM controls are just a cleverly written binding handlers.

Thanks to the attached properties and strong-typing nature of DotVVM, you also have IntelliSense in the editor, and you can bundle these pieces of infrastructure in your custom DLLs or NuGet packages and reuse them in multiple projects.

IntelliSense for attached properties

The FormHelpers class may be included as part of future releases of DotVVM Business Pack since this is quite common user requirement.

If you have any questions, feel free to ask on our Gitter chat.