Method overload resolution in C# 6.0: an interesting bug story

Recently at work I’ve been looking into migrating our projects from VS2013 to VS2017. As part of the process we decided to move from C# 5.0 to C# 7.0. It turned out that after the switch some of our projects won’t build anymore. I spent some time investigating the issue and found the outcome interesting so let me share my story with you.


Below is the code that caused issues. It is an interface declaration with two overloads of a single  Get  method.

The code itself was fine. However, if we try to call it like this:

strange things will happen. Under VS2013 the code will compile without issues. However, under VS2017 it will cause a compile error:

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C# in Depth: book notes

pobraneI just finished reading this must-read position for C# developers. I believe that it’s very easy to learn a programming
language to an extent that is sufficient for creating software. Because of that, one can easily lose motivation to dig deeper and gain better understanding of the language. C# in Depth is a proof of why one shouldn’t stop at this point. There is a lot to learn by looking at the details of a language, how it evolved and how some of it’s features are implemented.

I think the book is fantastic. I loved the author’s writing style which is very precise (very little hand waving) but not boring at the same time. It feels that he’s giving you just the right amount of detail.

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ngPoland – Angular Conference 2016

Today I attendend ngPoland – the first international conference devoted to Angular in Central Europe. I’ve had some really good time there and decided to share some of the amazing things I learned about.

First of all, I was surprised to learn how good some of the speakers were at catching people attention and making sure that everyone stays awake. The conference was pretty intense (I counted 15 talks) so it was quite a challange. It was inspiring to see how got can one become at public speaking and working with large audiences.

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“Scalability Rules: 50 Principles for Scaling Web Sites” review

Recently I decided to get into the habit of reading IT books regularly. To start with, I wanted read something about building scalable architectures. I did a quick research on Amazon and chose Scalability Rules: 50 Principles for Scaling Web Sites by Martin L. Abbott, Michael T. Fisher. Based on comments and reviews, it was supposed to be more on the technical side. I was slightly disappointed in this aspect. However, I think this is still a worthy read.

The book is divided into 13 chapters. Each of the chapters contains several rules. What stroke me is that these rules are very diverse. We’ve got some very, very general advice that could be applied to any kind of software development (e.g. Don’t overengineer, Learn aggressively, Be competent). We’ve got stuff for CTOs or IT directors in large corporations (e.g. Have at least 3 data centers, Don’t rely on QA to find mistakes). There are also some specific, technical rules – what I was after in the first place. I’m not convinced mixing these very different kinds of knowledge makes sense since they are probably targeted to different audiences (which is even acknowledge by the authors in the first chapter).

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Issues with asynchronous IO in web applications

Building servers with non-blocking IO has been quite popular these days. Tests have shown that it does actually improve scalability of web applications. However, my experience show that it comes at a cost. In this post I am going to discuss some negative aspects of writing asynchronous code based on Scala’s Futures.


Debugging exceptions in asynchronous programs is a pain. When issuing an asynchronous IO operation you provide a callback that should be executed when the operation returns. In most implementations, this callback might be executed on any thread (not necessarly the same thread that invoked the operation). Since call stack is local to the thread, the stacktrace that you get when handling an exception is not very informative. It will not trace back to the servlet so you may have hard time figuring out where what actually happened.

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Asynchronous programming in Scala vs C#

In one of my recent post I compared two different approaches that authors of Scala and C# chose to solve the same problem. This post is based on the same idea but the problem being solved is asynchronous programming.

What’s asynchronous programming?

Let me explain by giving you an example. If you have ever used a web framework you might have been wondering how it handles multiple concurrent requests from different users. The traditional approach is to spawn a new thread (or get one from a thread pool) for every request that comes in and release it once the request is served.

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Scala’s Option monad versus null-conditional operator in C#

Today I will talk about an awesome feature of C# 6.0. We will see how it can help us understand monads in Scala!

Null-conditional operator

Imagine we have a nested data model and want to call some method on a property nested deeply inside an object graph. Let’s assume that Article does not have to have an Author, the Author does not have to have an Address and the address does not have to have a City (for example this data can be missing from our database).

This is very unsafe code since we are at risk of NullReferenceException. We have to introduce some null checks in order to avoid the exception.

Yuck! So much boilerplater code to do a very simple thing. It’s really unreadable and confusing.

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Why I like C#: feature-wise comparison with Java

Recently I was browsing Quora and was quite surprised to stumble upon this question: Java vs C#. Is Microsoft finally closing the gap? I decided to have a closer look and found more of similiar questions there.

Furthermore, at the place where I am currently working at, I am the only person with .NET background amongst mostly JVM people. We are all working on Scala projects and my colleagues are often surprised when I tell them that this or that Scala feature is also available in C#.

This makes me want to write a blog post about how cool a language C# is, especially when compared with Java. I want to underline that I’m speaking only about the language features and not about things like popularity, cross-platformness, ability to deploy easily, etc.

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