I guess one of the most important issues in this topic is building an exception handling architecture in your application. This is interesting for many reasons. And the main reason, I think, is an apparent simplicity, which you don’t always know what to do with. All the basic constructs such as IEnumerable, IDisposable, IObservable, etc. have this property and use it everywhere. On the one hand, their simplicity tempts to use these constructs in different situations. On the other hand, they are full of traps which you might not get out. It is possible that looking at the amount of information we will cover you’ve got a question: what is so special about exceptional situations?

However, to make conclusions about building the architecture of exception classes we should learn some details about their classification. Because before building a system of types that would be clear for the user of code, a programmer should determine when to choose the type of error and when to catch or skip exceptions. So, let’s classify the exceptional situations (not the types of exceptions) based on various features.

Specifics of QueryProvider

QueryProvider can’t deal with this:

var result = _context.Humans
                      .Select(x => $"Name: {x.Name}  Age: {x.Age}")
                      .Where(x => x != "")
                      .ToList();

It can’t deal with any sentence using an interpolated string, but it’ll easily deal with this:

var result = _context.Humans
                      .Select(x => "Name " +  x.Name + " Age " + x.Age)
                      .Where(x => x != "")
                      .ToList();

The most painful thing is to fix bugs after turning on ClientEvaluation (exception for client-side calculation), since all Automapper profiles should be strictly analyzed for interpolation. Let’s find out what’s what and propose our solution to the problem.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

← Previous publications

Introduction

It’s time to talk about exceptions or, rather, exceptional situations. Before we start, let’s look at the definition. What is an exceptional situation?

This is a situation that makes the execution of current or subsequent code incorrect. I mean different from how it was designed or intended. Such a situation compromises the integrity of an application or its part, e.g. an object. It brings the application into an extraordinary or exceptional state.

But why do we need to define this terminology? Because it will keep us in some boundaries. If we don’t follow the terminology, we can get too far from a designed concept which may result in many ambiguous situations. Let’s see some practical examples:

 struct Number
 {
     public static Number Parse(string source)
     {
         // ...
         if(!parsed)
         {
             throw new ParsingException();
         }
         // ...
     }

     public static bool TryParse(string source, out Number result)
     {
        // ..
        return parsed;
     }
 }

This example seems a little strange, and it is for a reason. I made this code slightly artificial to show the importance of problems appearing in it. First, let’s look at the Parse method. Why should it throw an exception?

MessageBox — useful window for different GUI frameworks, but you can't find it in AvaloniaUI.
Let's try to do it.

February 2019 marked the release of ReactiveUI 9 — the cross-platform framework for building GUI applications on the Microsoft .NET platform. ReactiveUI is a tool for tight integration of reactive extensions with the MVVM design pattern. You could familiarize yourself with the framework via a series of videos or the welcome page of the documentation. The ReactiveUI 9 update includes numerous fixes and improvements, but probably the most crucial and interesting one is integration with the DynamicData framework, allowing you to work with dynamic collections in Reactive fashion. Let’s find out what we can use DynamicData for and how this powerful reactive framework works under the hood!

This week I spent coding my very first public pet-app based on Telegram chat bot which acts as a Bitcoin wallet and allows to send and receive tips between Telegram users and other so-called “Lightning Apps”. I assume that you are familiar with Bitcoin & Telegram in general, i’ll try to post short and without deep jump into details. More resources about Bitcoin can be found here and Telegram is simply an instant messenger that allows you to create your custom apps (chat-bots) using their platform.

What are the key points of such app?

• Allows to rate other users ideas and answers with real value instead of
  ‘virtual likes’. This brings online conversation to completely new level
• Real example of working micro-payment app which can act with other entities
  over internet using open protocol
• All the modules are open-source projects and can be easy re-used and adjusted
  for your own project. App does not relay on third-party commercial services.
  Even it falls under e-commerce field, which is currently almost closed, the app
  is based on open solutions.

What are the use-cases?

something like this…

With a variety of new tools and features announced at Android Dev Summit, special attention should be given to the In-App Updates (IAUs) API allowing developers to increase the speed of delivering features, bug-fixes and performance improvements to active users. Since this feature was finally released after Google I/O 2019, in this article I’ll deep dive on IAUs API, describe in details recommended user flows and provide with some code samples. Moreover, I'll share some experience of IAUs integration in the Pandao app, a marketplace platform for Chinese goods.

Code search and navigation are important features of any IDE. In Java, one of the commonly used search options is searching for all implementations of an interface. This feature is often called Type Hierarchy, and it looks just like the image on the right.

It's inefficient to iterate over all project classes when this feature is invoked. One option is to save the complete class hierarchy in the index during compilation since the compiler builds it anyway. We do this when the compilation is run by the IDE and not delegated, for example, to Gradle. But this works only if nothing has been changed in the module after the compilation. In general, the source code is the most up-to-date information provider, and indexes are based on the source code.

Finding immediate children is a simple task if we are not dealing with a functional interface. When searching for implementations of the Foo interface, we need to find all the classes that have implements Foo and interfaces that have extends Foo, as well as new Foo(...) {...} anonymous classes. To do this, it is enough to build a syntax tree of each project file in advance, find the corresponding constructs, and add them to an index.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

From idea to implementation: modifying the existing elliptic curve signature scheme to be deterministic and providing functions on it to obtain verifiable within the blockchain pseudorandom numbers.

Earlier this week, we released Visual Studio 2019 version 16.1 Preview 1 (see release notes). It’s the first preview of the first update to Visual Studio 2019. If you’re not already set up to get preview releases, then please do that now. The preview channel installs side-by-side with the release channel and they don’t interfere with each other. I highly recommend all extension authors install the preview.

Got the 16.1 preview installed now then? That’s great. Here are some features in it you might find interesting.

Java developers have access to a number of useful tools that help to write high-quality code such as the powerful IDE IntelliJ IDEA, free analyzers SpotBugs, PMD, and the like. The developers working on CUBA Platform have already been using all of these, and this review will show how the project can benefit even more from the use of the static code analyzer PVS-Studio.

---

Quick links

— The Road to Version 12
— First, Some Math
— The Calculus of Uncertainty
— Classic Math, Elementary and Advanced
— More with Polygons
— Computing with Polyhedra
— Euclid-Style Geometry Made Computable
— Going Super-Symbolic with Axiomatic Theories
— The n-Body Problem
— Language Extensions & Conveniences
— More Machine Learning Superfunctions
— The Latest in Neural Networks
— Computing with Images
— Speech Recognition & More with Audio
— Natural Language Processing
— Computational Chemistry
— Geographic Computing Extended
— Lots of Little Visualization Enhancements
— Tightening Knowledgebase Integration
— Integrating Big Data from External Databases
— RDF, SPARQL and All That
— Numerical Optimization
— Nonlinear Finite Element Analysis
— New, Sophisticated Compiler
— Calling Python & Other Languages
— More for the Wolfram “Super Shell”
— Puppeting a Web Browser
— Standalone Microcontrollers
— Calling the Wolfram Language from Python & Other Places
— Linking to the Unity Universe
— Simulated Environments for Machine Learning
— Blockchain (and CryptoKitty) Computation
— And Ordinary Crypto as Well
— Connecting to Financial Data Feeds
— Software Engineering & Platform Updates
— And a Lot Else…

ML.NET is an open-source and cross-platform machine learning framework (Windows, Linux, macOS) for .NET developers. Using ML.NET, developers can leverage their existing tools and skillsets to develop and infuse custom AI into their applications by creating custom machine learning models for common scenarios like Sentiment Analysis, Recommendation, Image Classification and more!.

Today we’re announcing the ML.NET 1.0 RC (Release Candidate) (version 1.0.0-preview) which is the last preview release before releasing the final ML.NET 1.0 RTM in 2019 Q2 calendar year.

Soon we will be ending the first main milestone of a great journey in the open that started on May 2018 when releasing ML.NET 0.1 as open source. Since then we’ve been releasing monthly, 12 preview releases so far, as shown in the roadmap below:

In this release (ML.NET 1.0 RC) we have initially concluded our main API changes. For the next sprint we are focusing on improving documentation and samples and addressing major critical issues if needed.

The goal is to avoid any new breaking changes moving forward.

In this post we'd like to share an interesting way of dealing with configuration of a distributed system.
The configuration is represented directly in Scala language in a type safe manner. An example implementation is described in details. Various aspects of the proposal are discussed, including influence on the overall development process.

(на русском)

Multithreading

Now let’s talk about thin ice. In the previous sections about IDisposable we touched one very important concept that underlies not only the design principles of Disposable types but any type in general. This is the object’s integrity concept. It means that at any given moment of time an object is in a strictly determined state and any action with this object turns its state into one of the variants that were pre-determined while designing a type of this object. In other words, no action with the object should turn it into an undefined state. This results in a problem with the types designed in the above examples. They are not thread-safe. There is a chance the public methods of these types will be called when the destruction of an object is in progress. Let’s solve this problem and decide whether we should solve it at all.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

Your friendly neighborhood .NET productivity team (aka. Roslyn) focuses a lot on improving the .NET coding experience. Sometimes it’s the little refactorings and code fixes that really improve your workflow. You may have seen many improvements in the previews, but for all of you who were eagerly awaiting the GA release here’s a few features you may enjoy!

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

0_0

0_0 is a totally valid Python expression.

We’re excited to announce the general availability of Visual Studio Live Share, and that it is now included with Visual Studio 2019! In the year since Live Share began its public preview, we’ve been working to enhance the many ways you collaborate with your team. This release is the culmination of that work, and all the things we’ve learned from you along the way.

If you haven’t heard of Live Share, it’s a tool that enables real-time collaborative development with your teammates from the comfort of your own tools. You’re able to share your code, and collaboratively edit and debug, without needing to clone repos or set up environments. It’s easy to get started with Live Share.