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Creating a simple ASP.NET 5 Markdown TagHelper

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

I've been dabbling a bit with the new ASP.NET 5 TagHelpers and I was wondering how easy it would be to create one.

I've created a simple Markdown TagHelper with the CommonMark implementation.

So let me show you what it is, what each line of code is doing and how to implement it in an ASP.NET MVC 6 application.

The Code
using CommonMark;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Razor.Runtime.TagHelpers;

namespace My.TagHelpers
{
    [HtmlTargetElement("markdown")]
    public class MarkdownTagHelper : TagHelper
    {
        public ModelExpression Content { get; set; }
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.TagMode = TagMode.SelfClosing;
            output.TagName = null;

            var markdown = Content.Model.ToString();
            var html = CommonMarkConverter.Convert(markdown);
            output.Content.SetContentEncoded(html);
        }
    }
}
Inspecting the code

Let's start with the HtmlTargetElementAttribute. This will wire the HTML Tag <markdown></markdown> to be interpreted and processed by this class. There is nothing stop you from actually having more than one target.

You could for example target element <md></md> by just adding [HtmlTargetElement("md")] and it would support both tags without any other changes.

The Content property will allow you to write code like this:

@model MyClass

<markdown content="@ViewData["markdown"]"></markdown>    
<markdown content="Markdown"></markdown>    

This easily allows you to use your model or any server-side code without having to handle data mapping manually.

TagMode.SelfClosing will force the HTML to use self-closing tag rather than having content inside (which we're not going to use anyway). So now we have this:

<markdown content="Markdown" />

All the remaining lines of code are dedicated to making sure that the content we render is actual HTML. output.TagName just make sure that we do not render the actual markdown tag.

And... that's it. Our code is complete.

Activating it

Now you can't just go and create TagHelpers and have them automatically served without wiring one thing.

In your ASP.NET 5 projects, go to /Views/_ViewImports.cshtml.

You should see something like this:

@addTagHelper "*, Microsoft.AspNet.Mvc.TagHelpers"

This will load all TagHelpers from the Microsoft.AspNet.Mvc.TagHelpers assembly.

Just duplicate the line and type-in your assembly name.

Then in your Razor code you can have the code bellow:

public class MyClass
{
    public string Markdown { get; set; }
}
@model MyClass
@{
    ViewData["Title"] = "About";
}
<h2>@ViewData["Title"].</h2>  

<markdown content="Markdown"/>

Which will output your markdown formatted as HTML.

Now whether you load your markdown from files, database or anywhere... you can have your user write rich text in any text box and have your application generate safe HTML.

Components used
Categories: Blogs

Should our front-end websites be server-side at all?

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

I’ve been toying around with projects like Jekyll, Hexo and even some hand-rolled software that will generate me HTML files based on data. The thought that crossed my mind was…

Why do we need dynamically generated HTML again?

Let me take examples and build my case.

Example 1: Blog

Of course the simpler examples like blogs could literally all be static. If you need comments, then you could go with a system like Disqus. This is quite literally one of the only part of your system that is dynamic.

RSS feed? Generated from posts. Posts themselves? Could be automatically generated from a databases or Markdown files periodically. The resulting output can be hosted on a Raspberry Pi without any issues.

Example 2: E-Commerce

This one is more of a problem. Here are the things that don’t change a lot. Products. OK, they may change but do you need to have your site updated right this second? Can it wait a minute? Then all the “product pages” could literally be static pages.

Product reviews? They will need to be “approved” anyway before you want them live. Put them in a servier-side queue, and regenerate the product page with the updated review once it’s done.

There’s 3 things that I see that would require to be dynamic in this scenario.

Search, Checkout and Reviews. Search because as your products scales up, so does your data. Doing the search client side won’t scale at any level. Checkout because we are now handling an actual order and it needs a server components. Reviews because we’ll need to approve and publish them.

In this scenario, only the Search is the actual “Read” component that is now server side. Everything else? Pre-generated. Even if the search is bringing you the list of product dynamically, it can still end up on a static page.

All the other write components? Queued server side to be processed by the business itself with either Azure or an off-site component.

All the backend side of the business (managing products, availability, sales, whatnot, etc.) will need a management UI that will be 100% dynamic (read/write).

Question

So… do we need dynamic front-end with the latest server framework? On the public facing too or just the backend?

If you want to discuss it, Tweet me at @MaximRouiller.

Categories: Blogs

You should not be using WebComponents yet

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

Have you read about WebComponents? It sounds like something that we all tried to achieve on the web since... well... a long time.

If you take a look at the specification, it's hosted on the W3C website. It smell like a real specification. It looks like a real specification.

The only issue is that Web Components is really four specifications. Let's take a look at all four of them.

Reviewing the specificationsHTML Templates

Specification

This specific specification is not part of the "Web components" section. It has been integrated in HTML5. Henceforth, this one is safe.

Custom Elements

Specification

This specification is for review and not for implementation!

Alright no let's not touch this yet.

Shadow DOM

Specification

This specification is for review and not for implementation!

Wow. Okay so this is out of the window too.

HTML Imports

Specification

This one is still a working draft so it hasn't been retired or anything yet. Sounds good!

Getting into more details

So open all of those specifications. Go ahead. I want you to read one section in particular and it's the author/editors section. What do we learn? That those specs were draft, edited and all done by the Google Chrome Team. Except maybe HTML Templates which has Tony Ross (previously PM on the Internet Explorer Team).

What about browser support?

Chrome has all the spec already implemented.

Firefox implemented it but put it behind a flag (about:config, search for properties dom.webcomponents.enabled)

Internet Explorer, they are all Under Consideration

What that tells us

Google is pushing for a standard. Hard. They built the spec, pushing the spec also very hary since all of this is available in Chrome STABLE right now. No other vendors has contributed to the spec itself. Polymer is also a project that is built around WebComponents and it's built by... well the Chrome team.

That tells me that nobody right now should be implementing this in production. If you want to contribute to the spec, fine. But WebComponents are not to be used.

Otherwise, we're only getting in the same issue we were in 10-20 years ago with Internet Explorer and we know it's a painful path.

What is wrong right now with WebComponents

First, it's not cross platform. We handled that in the past. That's not something to stop us.

Second, the current specification is being implemented in Chrome as if it was recommended by the W3C (it is not). Which may lead us to change in the specification which may render your current implementation completely inoperable.

Third, there's no guarantee that the current spec is going to even be accepted by the other browsers. If we get there and Chrome doesn't move, we're back to Internet Explorer 6 era but this time with Chrome.

What should I do?

As for what "Production" is concerned, do not use WebComponents directly. Also, avoid Polymer as it's only a simple wrapper around WebComponents (even with the polyfills).

Use other framework that abstract away the WebComponents part. Frameworks like X-Tag or Brick. That way you can benefit from the feature without learning a specification that may be obsolete very quickly or not implemented at all.

Categories: Blogs

Fix: Error occurred during a cryptographic operation.

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

Have you ever had this error while switching between projects using the Identity authentication?

Are you still wondering what it is and why it happens?

Clear your cookies. The FedAuth cookie is encrypted using the defined machine key in your web.config. If there is none defined in your web.config, it will use a common one. If the key used to encrypt isn't the same used to decrypt?

Boom goes the dynamite.

Categories: Blogs

Renewed MVP ASP.NET/IIS 2015

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

Well there it goes again. It was just confirmed that I am renewed as an MVP for the next 12 months.

Becoming an MVP is not an easy task. Offline conferences, blogs, Twitter, helping manage a user group. All of this is done in my free time and it requires a lot of time.But I'm so glad to be part of the big MVP family once again!

Thanks to all of you who interacted with me last year, let's do it again this year!

Categories: Blogs

Failed to delete web hosting plan Default: Server farm 'Default' cannot be deleted because it has sites assigned to it

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

So I had this issue where I was moving web apps between hosting plans. As they were all transferred, I wondered why it refused to delete them with this error message.

After a few click left and right and a lot of wasted time, I found this blog post that provides a script to help you debug and the exact explanation as to why it doesn't work.

To make things quick, it's all about "Deployment Slots". Among other things, they have their own serverFarm setting and they will not change when you change their parents in Powershell (haven't tried by the portal).

Here's a copy of the script from Harikharan Krishnaraju for future references:

Switch-AzureMode AzureResourceManager
$Resource = Get-AzureResource

foreach ($item in $Resource)
{
	if ($item.ResourceType -Match "Microsoft.Web/sites/slots")
	{
		$plan=(Get-AzureResource -Name $item.Name -ResourceGroupName $item.ResourceGroupName -ResourceType $item.ResourceType -ParentResource $item.ParentResource -ApiVersion 2014-04-01).Properties.webHostingPlan;
		write-host "WebHostingPlan " $plan " under site " $item.ParentResource " for deployment slot " $item.Name ;
	}

	elseif ($item.ResourceType -Match "Microsoft.Web/sites")
	{
		$plan=(Get-AzureResource -Name $item.Name -ResourceGroupName $item.ResourceGroupName -ResourceType $item.ResourceType -ApiVersion 2014-04-01).Properties.webHostingPlan;
		write-host "WebHostingPlan " $plan " under site " $item.Name ;
	}
}
      
    
Categories: Blogs

Switching Azure Web Apps from one App Service Plan to another

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

So I had to do some change to App Service Plan for one of my client. The first thing I was looking for was to do it under the portal. A few clicks and I'm done!

But before I get into why I need to move one of them, I'll need to tell you about why I needed to move 20 of them.

Consolidating the farm

First, my client had a lot of WebApps deployed left and right in different "Default" ServicePlan. Most were created automatically by scripts or even Visual Studio. Each had different instance size and difference scaling capabilities.

We needed a way to standardize how we scale and especially the size on which we deployed. So we came down with a list of different hosting plans that we needed, the list of apps that would need to be moved and on which hosting plan they currently were.

That list went to 20 web apps to move. The portal wasn't going to cut it. It was time to bring in the big guns.

Powershell

Powershell is the Command Line for Windows. It's powered by awesomeness and cats riding unicorns. It allows you to do thing like remote control Azure, import/export CSV files and so much more.

CSV and Azure is what I needed. Since we built a list of web apps to migrate in Excel, CSV was the way to go.

The Code or rather, The Script

What follows is what is being used. It's heavily inspired of what was found online.

My CSV file has 3 columns: App, ServicePlanSource and ServicePlanDestination. Only two are used for the actual command. I could have made this command more generic but since I was working with apps in EastUS only, well... I didn't need more.

This script should be considered as "Works on my machine". Haven't tested all the edge cases.

Param(
    [Parameter(Mandatory=$True)]
    [string]$filename
)

Switch-AzureMode AzureResourceManager
$rgn = 'Default-Web-EastUS'

$allAppsToMigrate = Import-Csv $filename
foreach($app in $allAppsToMigrate)
{
    if($app.ServicePlanSource -ne $app.ServicePlanDestination)
    {
        $appName = $app.App
		    $source = $app.ServicePlanSource
		    $dest = $app.ServicePlanDestination
        $res = Get-AzureResource -Name $appName -ResourceGroupName $rgn -ResourceType Microsoft.Web/sites -ApiVersion 2014-04-01
        $prop = @{ 'serverFarm' = $dest}
        $res = Set-AzureResource -Name $appName -ResourceGroupName $rgn -ResourceType Microsoft.Web/sites -ApiVersion 2014-04-01 -PropertyObject $prop
        Write-Host "Moved $appName from $source to $dest"
    }
}
    
Categories: Blogs

Microsoft Virtual Academy Links for 2014

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

So I thought that going through a few Microsoft Virtual Academy links could help some of you.

Here are the links I think deserve at least a click. If you find them interesting, let me know!

Categories: Blogs

Temporarily ignore SSL certificate problem in Git under Windows

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

So I've encountered the following issue:

fatal: unable to access 'https://myurl/myproject.git/': SSL certificate problem: unable to get local issuer certificate

Basically, we're working on a local Git Stash project and the certificates changed. While they were working to fix the issues, we had to keep working.

So I know that the server is not compromised (I talked to IT). How do I say "ignore it please"?

Temporary solution

This is because you know they are going to fix it.

PowerShell code:

$env:GIT_SSL_NO_VERIFY = "true"

CMD code:

SET GIT_SSL_NO_VERIFY=true

This will get you up and running as long as you don’t close the command window. This variable will be reset to nothing as soon as you close it.

Permanent solution

Fix your certificates. Oh… you mean it’s self signed and you will forever use that one? Install it on all machines.

Seriously. I won’t show you how to permanently ignore certificates. Fix your certificate situation because trusting ALL certificates without caring if they are valid or not is juts plain dangerous.

Fix it.

NOW.

Categories: Blogs

The Yoda Condition

Decaying Code - Maxime Rouiller - Sat, 04/30/2016 - 08:45

So this will be a short post. I would like to introduce a word in my vocabulary and yours too if it didn't already exist.

First I would like to credit Nathan Smith for teaching me that word this morning. First, the tweet:

Chuckling at "disallowYodaConditions" in JSCS… https://t.co/unhgFdMCrh — Awesome way of describing it. pic.twitter.com/KDPxpdB3UE

— Nathan Smith (@nathansmith) November 12, 2014

So... this made me chuckle.

What is the Yoda Condition?

The Yoda Condition can be summarized into "inverting the parameters compared in a conditional".

Let's say I have this code:

string sky = "blue";if(sky == "blue) {    // do something}

It can be read easily as "If the sky is blue". Now let's put some Yoda into it!

Our code becomes :

string sky = "blue";	if("blue" == sky){    // do something}

Now our code read as "If blue is the sky". And that's why we call it Yoda condition.

Why would I do that?

First, if you're missing an "=" in your code, it will fail at compile time since you can't assign a variable to a literal string. It can also avoid certain null reference error.

What's the cost of doing this then?

Beside getting on the nerves of all the programmers in your team? You reduce the readability of your code by a huge factor.

Each developer on your team will hit a snag on every if since they will have to learn how to speak "Yoda" with your code.

So what should I do?

Avoid it. At all cost. Readability is the most important thing in your code. To be honest, you're not going to be the only guy/girl maintaining that app for years to come. Make it easy for the maintainer and remove that Yoda talk.

The problem this kind of code solve isn't worth the readability you are losing.

Categories: Blogs

Validation inside or outside entities?

Jimmy Bogard - Fri, 04/29/2016 - 21:45

A common question I get asked, especially around a vertical slice architecture, is where does validation happen? If you’re doing DDD, you might want to put validation inside your entities. But personally, I’ve found that validation as part of an entity’s responsibility is just not a great fit.

Typically, an entity validating itself will do so with validation/data annotations on itself. Suppose we have a Customer and its First/Last names are “required”:

public class Customer
{
    [Required]
    public string FirstName { get; set; }
    [Required]
    public string LastName { get; set; }
}

The issue with this approach is twofold:

  • You’re mutating state before validation, so your entity is allowed to be in an invalid state.
  • There is no context of what the user was trying to do

So while you can surface these validation errors (typically from an ORM) to the end user, it’s not easy to line up the original intent with the implementation details of state. Generally I avoid this approach.

But if you’re all up in DDD, you might want to introduce some methods to wrap around mutating state:

public class Customer
{
  public string FirstName { get; private set; }
  public string LastName { get; private set; }
    
  public void ChangeName(string firstName, string lastName) {
    if (firstName == null)
      throw new ArgumentNullException(nameof(firstName));
    if (lastName == null)
      throw new ArgumentNullException(nameof(lastName));
      
    FirstName = firstName;
    LastName = lastName;
  }
}

Slightly better, but only slightly, because the only way I can surface “validation errors” are through exceptions. So you don’t do exceptions, you use some sort of command result:

public class Customer
{
  public string FirstName { get; private set; }
  public string LastName { get; private set; }
    
  public CommandResult ChangeName(ChangeNameCommand command) {
    if (command.FirstName == null)
      return CommandResult.Fail("First name cannot be empty.");
    if (lastName == null)
      return CommandResult.Fail("Last name cannot be empty.");
      
    FirstName = command.FirstName;
    LastName = command.LastName;
    
    return CommandResult.Success;
  }
}

Again, this is annoying to surface to the end user because I have one validation error at a time being returned. I can batch them up, but how do I correlate back to the field name on the screen? I really can’t. Ultimately, entities are lousy at command validation. Validation frameworks, however, are great.

Command validation

Instead of relying on an entity/aggregate to perform command validation, I entrust it solely with invariants. Invariants are all about making sure I can transition from one state to the next wholly and completely, not partially. It’s not actually about validating a request, but performing a state transition.

With this in mind, my validation centers around commands and actions, not entities. I could do something like this instead:

public class ChangeNameCommand {
  [Required]
  public string FirstName { get; set; }
  [Required]
  public string LastName { get; set; }
}

public class Customer
{
  public string FirstName { get; private set; }
  public string LastName { get; private set; }
    
  public void ChangeName(ChangeNameCommand command) {
    FirstName = command.FirstName;
    LastName = command.LastName;
  }
}

My validation attributes are on the command itself, and only when the command is valid do I pass it to my entities for state transition. Inside my entity, I’m responsible for successfully accepting a ChangeNameCommand and performing the state transition, ensuring my invariants are satisfied. In many projects, I wind up using FluentValidation instead:

public class ChangeNameCommand {
  public string FirstName { get; set; }
  public string LastName { get; set; }
}

public class ChangeNameValidator : AbstractValidator<ChangeNameCommand> {
  public ChangeNameValidator() {
    RuleFor(m => m.FirstName).NotNull().Length(3, 50);
    RuleFor(m => m.LastName).NotNull().Length(3, 50);
  }
}

public class Customer
{
  public string FirstName { get; private set; }
  public string LastName { get; private set; }
    
  public void ChangeName(ChangeNameCommand command) {
    FirstName = command.FirstName;
    LastName = command.LastName;
  }
}

The key difference here is that I’m validating a command, not an entity. And since entities themselves are not validation libraries, it’s much, much cleaner to validate at the command level. Because the command is the form I’m presenting to the user, any validation errors are easily correlated to the UI since the command was used to build the form in the first place.

Validate commands, not entities, and perform the validation at the edges.

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Categories: Blogs

Test Studio Web and Desktop R1 2016 Updates

Telerik TestStudio - Fri, 04/29/2016 - 20:10
The latest release of Test Studio is here with major updates across the board, including improved coding UX, to help you test your apps more easily than ever. 2016-04-22T19:14:55Z 2016-04-29T18:01:10Z Konstantin Petkov
Categories: Companies

Recapping the Test Studio 2016 R1 Release Webinar

Telerik TestStudio - Fri, 04/29/2016 - 20:10
During the latest Test Studio 2016 R1 release webinar you all asked some very good questions that were right on target. Let's recap the webinar with some Q&A. 2016-04-14T15:29:32Z 2016-04-29T18:01:10Z Iliyan Panchev
Categories: Companies

How We Test Software: Chapter Two—Telerik Platform

Telerik TestStudio - Fri, 04/29/2016 - 20:10
Have you wondered how the teams working on Telerik products test software? We continue with the next chapter in our detailed guide, giving you deeper insight into our very own processes. This chapter focuses on Telerik Platform. 2016-04-11T21:07:02Z 2016-04-29T18:01:10Z Angel Tsvetkov
Categories: Companies

Let the New Test Studio Turn You Into a Mobile Testing Hero

Telerik TestStudio - Fri, 04/29/2016 - 20:10
The first major Test Studio product update for this year is now live. Go grab your free evaluation copy, and keep on reading to learn what’s new, including enriched mobile testing with support for web apps and more. 2016-04-01T15:08:05Z 2016-04-29T18:01:10Z Antonia Bozhkova
Categories: Companies

How Our Telerik Teams Test Software: Chapter One

Telerik TestStudio - Fri, 04/29/2016 - 20:10
Have you wondered how the teams working on Telerik products test software? Today we launch a detailed guide, giving you deeper insight into our very own processes. 2016-03-22T14:34:15Z 2016-04-29T18:01:10Z Daniel Djambov
Categories: Companies

Telerik Test Studio and Selenium

Telerik TestStudio - Fri, 04/29/2016 - 20:10
Mixing different frameworks into one automated testing solution can lead to powerful results. Test Studio and Selenium are two frameworks that complement each other well. 2016-03-18T15:46:17Z 2016-04-29T18:01:10Z Iliyan Panchev
Categories: Companies

Product Notifications in Test Studio

Telerik TestStudio - Fri, 04/29/2016 - 20:10
With Product Notifications, Test Studio becomes easier to use than ever, helping you discover new functionality and save time. 2016-02-11T16:02:11Z 2016-04-29T18:01:10Z Konstantin Petkov
Categories: Companies

Looking Back and Ahead as We Recap the Test Studio Webinar

Telerik TestStudio - Fri, 04/29/2016 - 20:10
The latest updates to Telerik Test Studio have arrived. We recap what's new and upcoming here, which we also recently discussed in our webinar (which you can watch here). 2016-02-09T17:23:21Z 2016-04-29T18:01:10Z Iliyan Panchev
Categories: Companies

Looking Back and Ahead at the Telerik Test Studio Webinar

Telerik TestStudio - Fri, 04/29/2016 - 20:10
The latest updates from Test Studio are here, adding more mobile features and other enhancements. Learn about what’s new in an upcoming webinar. 2016-01-22T17:21:44Z 2016-04-29T18:01:10Z Antonia Bozhkova
Categories: Companies

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