To start with, I want to specify what is meant by a modular application in this article. So, a modular application will be considered an application, which consists of the so-called shell and a set of plug-in modules. There is no direct dependence between them, only via contracts. This allows independently modify each of the components, change their contents, etc. I think everyone knows the advantages of modular architecture.
Anyone who has ever developed applications that use a database has probably faced the problem of updating the database structure when the application is deployed and updated.
The most common approach is to create a set of SQL scripts to modify the database structure from version to version. Of course, there are paid tools, but they do not always solve the problem of full automation of the update.
Recently, I have often had to use the well-known Visitor pattern. I used to ignore this pattern and thought that it simply complicates the code. In this article, I will share my thoughts about this pattern. We will talk about pros and cons, as well as what tasks it helps to solve and how to simplify its use. The code will be in C#.
As I expected, Rule 8 from the article “Rules for Implementing TDD in Old Project” stating that we don’t need to test the algorithm of methods raised many “how” and “why” questions. When writing the previous article, it seemed obvious to me, so I did not go into much details on the matter. In this article, I provide a small sample code and two examples of how it could be tested.
The article “Sliding Responsibility of the Repository Pattern” raised several questions, which are very difficult to answer. Do we need a repository if the complete disregard of technical details is impossible? How complex must the repository be so that its addition can be regarded worth-while? The answer to these questions varies depending on the emphasis placed in the development of systems. Probably the most difficult question is the following: do you even need a repository? The problem of “flowing abstraction” and the growing complexity of coding with an increase in the level of abstraction do not allow to find a solution that would satisfy both sides of the fence. For example, in reporting, intention design leads to the creation of a large number of methods for each filter and sorting, and a generic solution creates a large coding overhead.
Some time ago, we started to adapt the system to the new market that requires support for time zones. Initial research was described in the previous article. Now the approach has slightly evolved under the influence of realities. This article describes the problems encountered during the discussions and the final decision that is implemented.
This article features a few tricks to reduce the size of the code resulting from the use of the ‘strategy’ pattern. As you can deduce from the title, all these tricks will be related to the usage of generic types.
1. Hierarchy of classes involved in magic rituals
Suppose we have an abstract ‘vehicle’ class that can move (the Move method). This class has 3 descendants: a car, a plane, and a rickshaw. Each of them implements the method in its own way: (more…)
The concept of good or bad design is relative. At the same time, there are some programming standards, which in most cases guarantee effectiveness, maintainability, and testability. For example, in object-oriented languages, this is the use of encapsulation, inheritance, and polymorphism. There is a set of design patterns that in a number of cases have a positive or negative effect on the application design depending on the situation. On the other hand, there are opposites, following which sometimes leads to the problem design.
During numerous discussions about the applicability of the Repository pattern, I noticed that people are divided into two groups. In this article, I will call them abstractionists and concretists. The difference between them is in the way they treat the pattern value. The former believe that a repository is worthwhile, as it allows disregarding details of data storing. The latter suppose there is no way to disregard these details, therefore, the concept of repository makes no sense and its usage is a waste of time. The dispute between these two groups usually turns into a Holy War. (more…)
I’d like to tell you straight off that this article will concern not threads in particular, but events in the context of threads in .NET. So, I won’t try arranging threads correctly (with all blocks, callbacks, canceling, etc.) There are many articles on this subject.
All examples are written in C# for the framework version 4.0 (in 4.6, everything is slightly easier, but still, there are many projects in 4.0). I will also try to stick to C# version 5.0.
Firstly, I’d like to note that there are ready delegates for the .Net event system that I highly recommend to use instead of inventing something new. For example, I frequently faced the following 2 methods for organizing events. (more…)