Mariusz Krzanowski blog

Tag: Code Sample

Long polling as a cure for message push mechanism


Many times in your life, you will have the situation when your server must push information to your customer. When you are not limited to HTTP/HTTPS you can setup TCP/IP connection and problems are solved. Unfortunately we are living in a world dominated by HTTP protocols. When you ask someone how to address such a challenge you can hear from your colleagues that Webhook ( is a solution for your problem. My goal is to convince you to try to think outside the box and focus on long pooling mechanisms.

Azure Functions V3 and disappearing function.json files


When I started migration process to Azure Function 3.0 of an existing project, I have discovered small, but painful inconvenience. The problem was that all function.json files were permanently removed from output folder just before Azure Function Tools func.exe was started. I have to confess it was very annoying. There were suggestions e.g. on StackOverflow or other sites to run PowerShell which copies files later – after emulator is started, but it was not a solution I like.

Exception filters to catch first thrown exception


This post is inspired by the book ‘C# in depth’ by Jon Skeet and presentation ‘Internals of Exceptions’ made by Adam Furmanek. The topic I want to focus on is stack unwinding when an exception is caught.

ConcurrentDictionary and race condition


The goal of this article is to show the problem of race condition while execution of GetOrAdd(TKey, Func<TKey, TValue>) method. The described problem has a few solutions. I will focus on one I found at StackOverflow, and I will explain why this solution works.

Double execution problem

Not everyone realizes that  GetOrAdd(TKey, Func<TKey, TValue>) can call multiple times the delegate resolving value for a single key. It is easy to prove this thesis with the following code.

SQL Trick – Multiple Values Query

Sometimes system flexibility makes the solution complicated 😉 . Imagine a ‘simple’ situation that you have a system in which a client can define new attribute and assign multiple values to it. Later, the client can assign these values to the Customers. If you do not plan to develop new attributes’ set every time a client wants to make a change, you will need to prepare a ‘dynamic’ structure in the database.

Resolving AD groups membership

Big companies have huge internal structures. The problem they have is that huge structures have to be mapped into a permission model. One company I worked for had over 300k groups in Active Directory. As worldwide organization they have multiple domains in AD forest. Of course, various groups have various memberships so the structure was really complicated.

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