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What's this about

After working on different projects, I've noticed that every one of them had some common problems, regardless of domain, architecture, code convention and so on. Those problems weren't challenging, just a tedious routine: making sure you didn't miss anything stupid and obvious. Instead of doing this routine on a daily basis I became obsessed with seeking solution: some development approach or code convention or whatever that will help me to design a project in a way that will prevent those problems from happening, so I can focus on interesting stuff. That's the goal of this article: to describe those problems and show you that mix of tools and approaches that I found to solve them.

Beginning with C# 8.0 on .NET Core 3.0, you can define an implementation when you declare a member of an interface. The most common scenario is to safely add members to an interface already released and used by innumerable clients.

In this tutorial, you'll learn how to:

• Extend interfaces safely by adding methods with implementations.
• Create parameterized implementations to provide greater flexibility.
• Enable implementers to provide a more specific implementation in the form of an override.

Hi All,

I’m in the process of implementing a new simple microservices-based project as an example of a step-by-step guide for those who had a hard time with a microservices architecture and are still looking for “another” good reference. Also, I would really appreciate thought through feedback and proposal to make this project a high-quality chunk of work.

There are tons of articles and source code examples. But, unfortunately, I could not find any reference with simple step-by-step instructions, without doing a deep dive into Docker, Event Store, a multitude of configurations, cloud deployment stuff, etc. I cloned several projects and tried to start playing with them, but you know, only God knows how to start them, which dependencies are missing and why all those scripts are failing with thousands of ERRORS.

For example, this eShop project from Microsoft contains all we need, but it is not so simple to figure out what is going on there, SQL database connection strings, Docker scripts fail, no How-Tos and I’m not sure it is super-simple architecture you need to start with.

No doubts that async/await pattern has significantly simplified working with asynchronous operations in C#. However, this simplification relates only to the situation when asynchronous operations are executed consequently. If we need to execute several asynchronous operations simultaneously (e.g. we need to call several micro-services) then we do not have many built-in capabilities and most probably Task.WhenAll will be used:

Task<SomeType1> someAsyncOp1 = SomeAsyncOperation1();
Task<SomeType2> someAsyncOp2 = SomeAsyncOperation2();
Task<SomeType3> someAsyncOp3 = SomeAsyncOperation3();
Task<SomeType4> someAsyncOp4 = SomeAsyncOperation4();
await Task.WhenAll(someAsyncOp1, someAsyncOp2, someAsyncOp4);
var result = new SomeContainer(
     someAsyncOp1.Result,someAsyncOp2.Result,someAsyncOp3.Result, someAsyncOp4.Result);

This is a working solution, but it is quite verbose and not very reliable (you can forget to add a new task to “WhenAll”). I would prefer something like that instead:

var result =  await 
    from r1 in SomeAsyncOperation1()
    from r2 in SomeAsyncOperation2()
    from r3 in SomeAsyncOperation3()
    from r4 in SomeAsyncOperation4()
    select new SomeContainer(r1, r2, r3, r4);

Further I will tell you what is necessary for this construction to work...

I'm putting part of older WebForms portions of my site that still run on bare metal to ASP.NET Core and Azure App Services, and while I'm doing that I realized that I want to make sure my staging sites don't get indexed by Google/Bing.

I already have a robots.txt, but I want one that's specific to production and others that are specific to development or staging. I thought about a number of ways to solve this. I could have a static robots.txt and another robots-staging.txt and conditionally copy one over the other during my Azure DevOps CI/CD pipeline.

Then I realized the simplest possible thing would be to just make robots.txt be dynamic. I thought about writing custom middleware but that sounded like a hassle and more code that needed. I wanted to see just how simple this could be.

Avalonia ui is a delightful framework to which you want to return again and again. So let's go back to it again and look at some of the features with my message box.

Every now and then we create our own problems with our own hands… with our vision of the world… with our inaction… with our laziness… and with our fears. As a result, it seems to become very convenient to swim in the public flow of sewage patterns… because it is warm and fun, and the rest does not matter – we can smell round. But after a fail comes the realization of the simple truth – instead of generating an endless stream of causes, self-pity and self-justification, it is enough just to do what you consider the most important for yourself. This will be the starting point for your new reality.

For me, the written below is just such a starting point. The way is expected to be lingering…

Today, we are announcing .NET Core 3.0 Preview 6. It includes updates for compiling assemblies for improved startup, optimizing applications for size with linker and EventPipe improvements. We’ve also released new Docker images for Alpine on ARM64.

• Download .NET Core 3.0 Preview 6 right now on Windows, macOS and Linux.

• Release notes have been published at dotnet/core. An API diff between Preview 5 and 6 is also available.

• ASP.NET Core and EF Core are also releasing updates today.

• If you missed it, check out the improvements we released in .NET Core 3.0 Preview 5, from last month.

I have originally posted this article in CodingSight blog
The second part of the article is available here

The need to do things in an asynchronous way – that is, dividing big tasks between multiple working units – was present long before the appearance of computers. However, when they did appear, this need became even more obvious. It is now 2019, and I’m writing this article on a laptop powered by an 8-core Intel Core CPU which, in addition to this, is simultaneously working on hundreds of processes, with the number of threads being even larger. Next to me, there lies a slightly outdated smartphone which I bought a couple of years ago – and it also houses an 8-core processor. Specialized web resources contain a wide variety of articles praising this year’s flagship smartphones equipped with 16-core CPUs. For less then $20 per hour, MS Azure can give you access to a 128-core virtual machine with 2 TB RAM. But, unfortunately, you cannot get the most out of this power unless you know how to control interaction between threads.

Since I’ve been working with the community on porting desktop applications from .NET Framework to .NET Core, I’ve noticed that there are two camps of folks: some want a very simple and short list of instructions to get their apps ported to .NET Core while others prefer a more principled approach with more background information. Instead of writing up a “Swiss Army knife”-document, we are going to publish two blog posts, one for each camp:

• This post is the simple case. It’s focused on simple instructions and smaller applications and is the easiest way to move your app to .NET Core.
• We will publish another post for more complicated cases. This post will focus more on non-trivial applications, such WPF application with dependencies on WCF and third-party UI packages.

If you prefer watching videos instead of reading, here is the video where I do everything that is described below.

It's not a secret that Microsoft has been working on the 8-th version of C# language for quite a while. The new language version (C# 8.0) is already available in the recent release of Visual Studio 2019, but it's still in beta. This new version is going to have a few features implemented in a somewhat non-obvious, or rather unexpected, way. Nullable Reference types are one of them. This feature is announced as a means to fight Null Reference Exceptions (NRE).

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.

Support of Visual Studio 2019 in PVS-Studio affected a number of components: the plugin itself, the command-line analyzer, the cores of the C++ and C# analyzers, and a few utilities. In this article, I will briefly explain what problems we encountered when implementing support of the IDE and how we addressed them.

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?

I notice that people often use construction like this:

var length = array.Length;
for (int i = 0; i < length; i++) {
    //do smth
}

They think that having a call to the Array.Length on each iteration will make CLR to take more time to execute the code. To avoid it they store the length value in a local variable.
Let’s find out (once and for all !) if this is a viable thing or using a temporary variable is a waste of time.

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!

We are excited to announce the release of ML.NET 1.0 today.  ML.NET is a free, cross-platform and open source machine learning framework designed to bring the power of machine learning (ML) into .NET applications.

https://github.com/dotnet/machinelearning 

Get Started: http://dot.net/ml

Intro

.NET is a relative newcomer in the open-source world, and its popularity is nowhere near mainstream platforms like Node.js. So you can imagine there're few tutorials that deal with .NET and frameworks such as ASP.NET on Heroku. And those that do, probably won't use containers.

Do you see C#/.NET here? Yes, me neither.