library

Jan

2019

Integrate crypto payments into your .Net applications with AtomicPay

If you have been following along, you may have noticed that I am discovering the cryptocurrency space lately. Today I want to introduce you to AtomicPay, a crypto payment processor that uses a different approach than traditional processors.

Why AtomicPay?

I have been thinking quite some time about how one can implement crypto payments into apps, be it desktop or mobile apps. Ever since then, it was clear for me that I need a solution where the payment happens between me and the customer directly, but all the infrastructure to handle invoicing etc. has to be handled from the outside.

Traditional payment processors often provide their service with a custodial wallet – you do not have control of the keys, so it is not really your wallet, just the grant to use it. Processing incoming transactions to this custodial wallet are routed through another wallet of the service, where those processors take their fees and process the reduced payment to your custodial wallet.

Security and Privacy

When it comes to crypto payments, there is always one problem: the balance between the ease of using and security/privacy. If you are looking at some other non-custodial services, they are providing payment processing by just using a single wallet address. Even if this is the easiest way to use crypto payments, it has some fundamental issues:

makes it way too easy to monitor transactions of a business/merchant entity
easy target for man-in-the-middle attacks
accountability issues (imagine 10 people paying the same amount, but for different products at nearly the same time)

Do you really want to put you and your customer/user at this risk? Surely not!

AtomicPay’s different approach

AtomicPay follows a different route. It provides an invoicing infrastructure that is easy to use, but payments are directly between merchant and customer.

It relies on the well established Electrum wallets. Never used any Electrum wallet before? No worries, AtomicPay helps you to initialize the wallet with step-by-step tutorials.

Electrum wallets are (optionally) SegWit-enabled, HD (hierarchical determistic) wallets. This means that for every incoming transcation, a new address is generated from your keys. Even though you could do multiple times, every address should be used only once. This makes attacks from the outside significantly harder and protects both you and your customer/user.

AtomicPay itself only has reading access – it can watch transactions, but never initialize any transfer out of the wallet of your funds. Atomicpay is able to calculate new valid receiver addresses for your Electrum wallet because of the BIP 0032 protocol by using your public key, which is the only thing you need to insert into their website.

AtomicPay features

AtomicPay provides quite a bunch of features:

on-the-fly PayUrl generation (QuickPay)
monitoring of incoming payments
notifications via Mail and Webhook
free-to-use REST API
very low fees
and more…

Introducing AtomicPay.Net SDK

As AtomicPay convinced me to be a valuable solution for crypto payments, I started to create a new library for their API. The SDK makes it very simple to call all endpoints and to integrate it into your .NET applications. The library is available on Github and as NuGet package. You’ll find informations on how to use the library on Github as well. My repo will also be forked into AtomicPay’s Github account soon and gain a bit more visibility this way.

What’s next?

The library is only the first step and lays the groundwork for more things to come, namely:

Webhook code sample with Azure Function and Notificationhub
Xamarin component for AtomicPay
Administration app for merchants (iOS and Android)

If you have ideas or questions on the library, feel free to ping me on the well known social accounts or leave a comment under this post. As always, I hope the library will be helpful.

Until the next post, happy coding, everyone!

Disclaimer: I am contributing to this project with code written by me under the MIT License. Future contributions may contain their own (and different) disclaimer. I am not getting paid for my contributions to the project.

Please note that none of my crypto related posts is an investment or financial advice. As crypto currencies are volatile and risky, you should only invest as much as you can afford to lose. Always do your own research!

Oct

2018

Introducing Coinpaprika and announcing C# API Client

As I am diving deeper and deeper into the world of cryptocurrencies, I am exploring quite some interesting products. One of them is Coinpaprika, a market research site with some extensive information on every coin they have listed.

What is Coinpaprika?

In the world of cryptocurrencies, there are several things one needs to discover before investing. Starting with information on the project and its digital currencies, the persons behind a project as well as their current value and its price, there is a lot of data to walk through before investing. Several sites out there are providing aggregated information, and even provide APIs for us developers. However, most of them are

extremely rate limited
freemium with a complex pricing model
slow

Why Coinpaprika?

A lot of services that provide aggregated data rely on data of the big players like CoinMarketCap. Coinpaprika, however, has a different strategy. They are pulling their data from a whopping number of 176 exchanges into their own databases, without any proxy. They have their own valuation system and a very fast refreshing rate (16 000 price updates per minute). If you have some time and want to compare how prices match up with their competition, Coinpaprika even implemented a metrics page for you. In my personal experience, their data is more reliable average to those values I see on those exchanges I deal with (Binance, Coinbase, BitPanda, Changelly, Shapeshift).

Coinpaprika API and Clients

Early last week, I discovered Coinpaprika on Steemit. They announced their API is now available to the general public along with clients for PHP, GO, Swift and NodeJS. Coinpaprika has also a WordPress plugin and an embeddable widget (on a coin’s detail page) that allows you to easily show price information on your website. After discovering their site, I got in contact with them to discuss a possible C# implementation for several reasons:

very generous rate limits (25 920 00 requests per month, others are around 6 000 to 10 000), which enables very different implementation scenarios
their API is fast like hell
their independence from third parties besides exchanges
their very catchy name (just being honest)

A few days later, I was able to discuss the publication of the C# API client implementation I wrote with them. I am happy to announce that you can now download the C# API Client from Nuget or fork it from my Github repository. They will also link to it from their official API repository soon. The readme-file on Github serves as documentation as well and shows how to easily integrate their data into your .NET apps. The library itself is written in .NET Standard 2.0. If there is the need to target lower versions, feel free to open a pull request on Github. The Github repo contains also a console tester application.

Conclusion

If you need reliable market data and information on the different projects behind all those cryptocurrencies, you should evaluate Coinpaprika. They aggregate their data without any third party involved and provide an easy to use and blazing fast API. I hope my contribution in form of the C# API client will be helpful for some of you out there.

If you like their product as much as I do, follow them:

Twitter: https://twitter.com/coinpaprika
Facebook: https://www.facebook.com/coinpaprika/
Steemit: https://steemit.com/@coinpaprika
Medium: https://medium.com/coinpaprika
Telegram: https://t.me/Coinpaprika

Happy coding, everyone!

Apr

2018

WordPressReader (Standard) version 1.2.0 focuses on improving performance

The update contains several improvements to the HttpClientimplementation, which should improve performance of the library a lot:

all handlers now use one static HttpClientinstance. HttpClientis built to use it that way, and there is also no problem with multiple request handled by that instance. So everyone should use it in that way
the library is now actively enforcing gzip/deflate compression to make responses faster, especially when requesting bigger lists of items (if you want do deactivate it on the managed implementation, pass in falsewith the new useCompressionparameter with your call to the SetupClientmethod
deserialization by default now happens directly from the HttpResponsestream instead of first converting it to a string
added an API to pass in your own HttpClientinstance instead of the managed one (you could even use one static instance for your whole app this way to improve performance even further). To do so, just use the newly added method SetCustomClient(HttpClient client)on your handler instances.

I made this changes working without breaking existing implementations. Just by updating the library, you will get a better performance.

I also updated the source code on GitHub. If you just want to update the library, the update is already available on NuGet.

Happy coding, everyone!

P.S.
If you want to see the library in a live app, you can download my official blog reader app (which is written around it as a Xamarin.Formsapp) here:

iOS Android Windows 10

Mar

2018

WordPressReader (Standard) library is now available on Nuget

I am happy to announce my new WordPressReader (Standard) library that is available on NuGet now. It is written in .netStandard 1.4 which enables you to use it in a lot of of places. As the name suggests, it focuses on reading tasks against the WordPress API.

Features:

get, search and filter posts
get pages
get and filter categories
get, search and filter tags
get comments
post anonymous comments (needs additional work on the WordPress site)
get basic user info

The library uses a generic WordPressEntity model implementation, which makes it easy to implement and extend. You can always get the raw json-value as well. The additional Error property on every model makes it easy to handle API errors properly. You can read the full documentation in the GitHub Wiki.

If you have problems with the library or want to contribute, you can do so on the GitHub repo.

Happy coding, everyone!

P.S.
If you want to see the library in a live app, you can download my official blog reader app (which is written around it) here:

iOS Android Windows 10

Oct

2014

How to create a folder in Windows Phone 8.1 Pictures Library (and save/read files into/from it)

Some of you might have noticed that UniShare has its own folder in your devices picture library. Also some other apps like WhatsApp or Tweetium have it. The advantages of your app’s own folder are clear:

easier to get images into your app
user can always reflect which pictures come from your app
another presence of your app within the OS
higher remember rate for your app at the user site (which leads to more frequent usage of your app)

This post will show you how easy it is to generate a folder into the Pictures Library as well as save and read files into/from this folder.

Preparation

First, you need to add this using statements to your app:

using Windows.Storage;
using Windows.Storage.Streams;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Imaging;

Next, add the Picture Library capabilities to your app’s Package.appmanifest.

If you have a 8.1 Silverlight app, you need to add it to both the Package.appmanifest as well as the WMAppManifest.xml:

Then we are already able to generate our folder with this single line of code (counts for both Silverlight and Runtime apps):

StorageFolder appFolder= await KnownFolders.PicturesLibrary.CreateFolderAsync("myCustomAppFolder", CreationCollisionOption.OpenIfExists);

You should always use the CreateFolderAsync method together with the CollisionOption ‘OpenIfExists’. This way, your app will open it every time you are going to save a file, but creates the folder if it does not exist yet. If you now go to your pictures library, you will not see your folder yet, although it is there (use a File Manager app to check it if you want). Folders do only get populated when they have content. This is what the next step is about.

Save an image file

Saving an image is also pretty straight forward. First we are generating a StorageFile within our folder:

StorageFile myfile= await appFolder.CreateFileAsync("myfile.jpg", CreationCollisionOption.ReplaceExisting);

This generates a File Container that we can write our image to. To save the image we are going to asynchronously write the Stream of our image into it:

//asuming we have an Image control, replace this with your local code
var img = myImage.Source as WriteableBitmap;
//get fresh drawn image 
img.Invalidate();

using (Stream stream = await myfile.OpenStreamForWriteAsync())
{
   img.SaveJpeg(stream, img.PixelWidth, img.PixelHeight, 0, 100);
}

This code works for both a Windows Phone 8.1 Silverlight and Runtime apps. If you now go to your Pictures library, you will see your app’s folder as well as your saved image. Pretty easy, right?

Read images from our app’s folder

Reading an image file is pretty easy as well. Here is the code:

//open the picture library
StorageFolder libfolder = KnownFolders.PicturesLibrary;
//get all folders first
IReadOnlyList<StorageFolder> folderList = await libfolder.GetFoldersAsync();
//select our app's folder
var appfolder = folderList.FirstOrDefault(f => f.Name.Contains("myCustomAppFolder"));
//get the desired file (assuming you know the file name)
StorageFile picfile = await appPicturesFolder.GetFileAsync("myfile.jpg");
//generate a stream from the StorageFile
var stream = await picfile.OpenAsync(FileAccessMode.Read);
//generate a new image and set the source to our stream
BitmapImage img = new BitmapImage();
img.SetSource(stream);

//todo: work with the image

To get our generated folder, we need to fetch a list of folders in the library using the StorageFolder.GetFoldersAsync() method. We then query this list for our app’s folder. If you want to get a list of all pictures in your folder, you can use the StorageFile.GetFilesAsync() method. What I have done above is to load our saved single file. Finally, I opened a stream from this file and assigned it to a new BitmapImage, which can be used in our app.

There are also a lot of other options one can do with these folders and files, this is a very common scenario.

As always, I hope this post is helpful for some of you.

Sep

2014

WordPressUniversal – a PCL library for WordPress based C# mobile apps

As I have already developed a news reader app for my blog, I got asked quite a few times if I want to share my code to help others creating their apps. As I need to redesign my blog reader to match the latest OS features of Windows and Windows Phone, I decided to create my WordPressUniversal library.

Automattic, the company behind WordPress, integrated a powerful JSON API into their JetPack plugin. My library is based on this API. Please make sure the JSON API is active on the blog you are developing your app for.

The library currently provides the following features:

getting a list posts or pages
getting a list of all categories
getting a list of comments for the site and single posts
supports Windows Phone 8 & 8.1 Silverlight, Windows Phone 8.1 RT, Windows 8, Xamarin.iOS and Xamarin.Android

The library deserializes all data into C# objects you can immediately work with.

It is still a work in progress, but as it provides already a bunch of options to get you started, I am making this public already.

I am constantly working on the library, so be sure to follow the project along.

Note: JetPack’s JSON API does not support guest commenting at the moment. I already reached out to Automattic to (hopefully) find a solution for this. If you cannot wait, Disqus has a portable solution for Windows Phone apps.

Please make sure to see the documentation on my GitHub page.

If you have any questions, idea, wishes for me, just post a comment here or ping on Twitter.

Happy coding everyone!

Why AtomicPay?

Security and Privacy

AtomicPay’s different approach

AtomicPay features

Introducing AtomicPay.Net SDK

What’s next?

Until the next post, happy coding, everyone!

What is Coinpaprika?

Why Coinpaprika?

Coinpaprika API and Clients

Conclusion

Happy coding, everyone!

Preparation

Save an image file

Read images from our app’s folder

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