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Dynamic Xamarin Forms From XAML and JSON

Daniel Cazzulino's Blog - Mon, 05/25/2015 - 01:00

Yes, I’m well aware that the official API set for Xamarin.Forms only allows loading the compiled XAML into its “owning” view, using the LoadFromXaml<TView>(this TView view, Type callingType) extension method from the Xamarin.Forms.Xaml.Extensions class. And this is of course the actual real and supported way of doing it (for whatever reason, I’m not part of the Xamarin.Forms team :)).

But, being just a .NET assembly, I got curious as to how they loaded that XAML in that case. So a bit of .NET Reflector revealed the internal Xamarin.Forms.Xaml.XamlLoader class, with the following nice overload:

public static void Load(BindableObject view, string xaml)

So nothing prevents us from invoking that via reflection, you know? ;). Of course that is hardly a well-performing way of developing an entire app, but if you happen to need it for something, it’s totally doable and works acceptably well IMHO. I turned it into an extension method and was back in business in no time.

Another thing I was pretty excited to try out with this new knowledge, was a way to dynamically bind data too, so that I could load a dynamic view, then a dynamic data/view model (using JSON, but why not also any arbitrary key/value dictionary?), and have the app display both, bi-directional data binding and all.

For this I did have to send a PR to the Xamarin.Forms team for a little feature contribution, and they thankfully merged it :). It’s currently available in the pre-release nuget package for Xamarin.Forms:

PM> Install-Package Xamarin.Forms -Pre

This feature allows the BindingContext to provide its own reflection via the System.Reflection.IReflectableType interface. The implementation of that interface isn’t exactly trivial (I’d have liked it better if ICustomTypeDescriptor was available for PCLs) but it’s like 99% boilerplace. So I’ve made it generic enough that it can be reused for other dynamic models. I implemented an IDictionary-based model as well as a Linq to JSON-based JsonModel.

For convenience, I’ve put it all in a Xamarin.Forms.Dynamic package that takes a dependency on the pre-release Xamarin.Forms package:

PM> Install-Package Xamarin.Forms.Dynamic -Pre

With that in place, you can simpy do:

var page = new ContentPage();
string xaml = // load XAML string from wherever.
string json = // load JSON string from wherever.
page.LoadFromXaml(xaml);
page.BindingContext = JsonModel.Parse(json);

And that will do exactly what my Xamarin Forms Player demo does :). Of course, there is a tiny bit more involving trivial SignalR + Azure in there too, to send the payloads from VS to the app on the device, but that’s also available to explore if you want to see how I did it. Quite a few asked about this at the Xamarin event we did a few days ago at Microsoft Argentina, so there you go ;)

Categories: Blogs

Fix: Error occurred during a cryptographic operation.

Decaying Code - Maxime Rouiller - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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 - Mon, 05/25/2015 - 00:13

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

Do you have your own Batman Utility Belt?

Decaying Code - Maxime Rouiller - Mon, 05/25/2015 - 00:13
Just like most of us on any project, you (yes you!) as a developer must have done the same thing over and over again. I'm not talking about coding a controller or accessing the database.

Let's check out some concrete examples shall we?

  • Have you ever setup HTTP Caching properly, created a class for your project and call it done?
  • What about creating a proper Web.config to configure static asset caching?
  • And what about creating a MediaTypeFormatter for handling CSV or some other custom type?
  • What about that BaseController that you rebuild from project to project?
  • And those extension methods that you use ALL the time but rebuild for each projects...

If you answered yes to any of those questions... you are in great risk of having to code those again.

Hell... maybe someone already built them out there. But more often than not, they will be packed with other classes that you are not using. However, most of those projects are open source and will allow you to build your own Batman utility belt!

So once you see that you do something often, start building your utility belt! Grab those open source classes left and right (make sure to follow the licenses!) and start building your own class library.

NuGet

Once you have a good collection that is properly separated in a project and that you seem ready to kick some monkey ass, the only way to go is to use NuGet to pack it together!

Checkout the reference to make sure that you do things properly.

NuGet - Publishing

OK you got a steamy new hot NuGet package that you are ready to use? You can either push it to the main repository if your intention is to share it with the world.

If you are not ready quite yet, there are multiple way to use a NuGet package internally in your company. The easiest? Just create a Share on a server and add it to your package source! As simple as that!

Now just make sure to increment your version number on each release by using the SemVer convention.

Reap the profit

OK, no... not really. You probably won't be money anytime soon with this library. At least not in real money. Where you will gain however is when you are asked to do one of those boring task yet over again in another project or at another client.

The only thing you'll do is import your magic package, use it and boom. This task that they planned would take a whole day? Got finished in minutes.

As you build up your toolkit, more and more task will become easier to accomplish.

The only thing left to consider is what NOT to put in your toolkit.

Last minute warning

If you have an employer, make sure that your contract allows you to reuse code. Some contracts allows you to do that but double check with your employer.

If you are a company, make sure not to bill your client for the time spent building your tool or he might have the right to claim them as his own since you billed him for it.

In case of doubt, double check with a lawyer!

Categories: Blogs

Software Developer Computer Minimum Requirements October 2014

Decaying Code - Maxime Rouiller - Mon, 05/25/2015 - 00:13

I know that Scott Hanselman and Jeff Atwood have already done something similar.

Today, I'm bringing you the minimum specs that are required to do software development on a Windows Machine.

P.S.: If you are building your own desktop, I recommend PCPartPicker.

ProcessorRecommendation

Intel: Intel Core i7-4790K

AMD: AMD FX-9590

Unless you use a lot of software that supports multi-threading, a simple 4 core here will work out for most needs.

MemoryRecommendation

Minimum 8GB. 16GB is better.

My minimum requirement here is 8GB. I run a database engine and Visual Studio. SQL Server can easily take 2Gb with some big queries. If you have extensions installed for Visual Studio, it will quickly raise to 1GB of usage per instance and finally... Chrome. With multiple extensions and multiple pages running... you will quickly reach 4GB.

So get 8GB as the bare minimum. If you are running Virtual Machines, get 16GB. It won't be too much. There's no such thing as too much RAM when doing software development.

Hard-driveRecommendation

512 GB SSD drive

I can't recommend enough an SSD. Most tools that you use on a development machine will require a lot of I/O. Especially random read. When a compiler starts and retrieve all your source code to compile, it will need to read from all those file. Same thing if you have tooling like ReSharper or CodeRush. I/O speed is crucial. This requirement is even more important on a laptop. Traditionally, PC maker put a 5200RPM HDD on a laptop to reduce power usage. However, 5200 RPM while doing development will be felt everywhere.

Get an SSD.

If you need bigger storage (terabytes), you can always get a second hard-drive of the HDD type instead. Slower but capacities are also higher. On most laptop, you will need external storage for this hard drive so make sure it is USB3 compatible.

Graphic Card

Unless you do graphic rendering or are working with graphic tools that require a beast of a card... this is where you will put the less amount of money.

Make sure to get enough of them for your amount of monitors and that they can provide the right resolution/refresh rate.

Monitors

My minimum requirement nowadays is 22 inches. 4K is nice but is not part of the "minimum" requirement. I enjoy a 1920x1080 resolution. If you are buying them for someone else, make sure they can be rotated. Some developers like to have a vertical screen when reading code.

To Laptop or not to Laptop

Some company go Laptop for everyone. Personally, if the development machine never need to be taken out of the building, you can go desktop. You will save a bit on all the required accessories (docking port, wireless mouse, extra charger, etc.).

My personal scenario takes me to clients all over the city as well as doing presentations left and right. Laptop it is for me.

Categories: Blogs

SVG are now supported everywhere, or almost

Decaying Code - Maxime Rouiller - Mon, 05/25/2015 - 00:13

I remember that when I wanted to draw some graphs on a web page, I would normally have 2 solutions

Solution 1 was to have an IMG tag that linked to a server component that would render an image based on some data. Solution 2 was to do Adobe Flash or maybe even some Silverlight.

Problem with Solution 1

The main problem is that it is not interactive. You have an image and there is no way to do drilldown or do anything with it. So unless your content was simple and didn't need any kind of interaction or simply was headed for printing... this solution just wouldn't do.

Problem with Solution 2

While you now get all the interactivity and the beauty of a nice Flash animation and plugin... you lost the benefits of the first solution too. Can't print it if you need it and over that... it required a plugin.

For OSX back in 2009, plugins were the leading cause of browser crash and there is nothing that stops us from believing that similar things aren't true for other browsers.

The second problem is security. A plugin is just another attack vector on your browser and requiring a plugin to display nice graphs seem a bit extreme.

The Solution

The solution is relatively simple. We need a system that allows us to draw lines, curves and what not based on coordinate that we provide it.

That system should of course support colors, font and all the basic HTML features that we know now (including events).

Then came SVG

SVG has been the main specification to drawing anything vector related in a browser since 1999. Even though the specification started at the same time than IE5, it wasn't supported in Internet Explorer until IE9 (12 years later).

The support for SVG is now in all major browsers from Internet Explorer to FireFox and even in your phone.

Chances are that every computer you are using today can render SVG inside your browser.

So what?

SVG as a general rule is under used or thought of something only artists do or that it's too complicated to do.

My recommendation is to start cracking today on using libraries that leverage SVG. By leveraging them, you are setting yourself apart from others and can start offering real business value to your clients right now that others won't be able to.

SVG has been available on all browsers for a while now. It's time we start using it.

Browsers that do not support SVG
  • Internet Explorer 8 and lower
  • Old Android device (2.3 and less), partial support for 3-4.3
References, libraries and others
Categories: Blogs

New Features of SQL Server 2016

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
In this article you will learn the new features of SQL Server 2016.
Categories: Communities

Table Splitting Select Data Using Code First Approach

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
This article shows how to do table splitting and select data operations using Code First Approach.
Categories: Communities

Handling Duplication In SQL

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
In this article we will learn how to handle the duplication.
Categories: Communities

What SharePoint Online Is

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
In this article, you will learn the purpose and role of SharePoint Online.
Categories: Communities

Table Splitting Delete Data Using Code First Apporach

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
This article shows how to do table splitting and delete data operations using Code First Approach.
Categories: Communities

How to Create Custom Inline Helper Methods in ASP.Net MVC

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
In this article we will learn how to create Custom Inline Helper Methods in ASP.NET MVC.
Categories: Communities

Table Splitting Insert Data Using Code First Approach

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
This article shows how to do table splitting and insert data operations using Code First Approach
Categories: Communities

Common Hands-on Sample For AngularJS Developers: Part 2

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
Part 2 of this series contains 10 common hands-on samples needed for an AngularJS project.
Categories: Communities

Table Splitting Update Data Using Code First Approach

C-Sharpcorner - Latest Articles - Sun, 05/24/2015 - 08:00
This article shows how to do table splitting and update data operations using Code First Approach.
Categories: Communities