Specification Design Pattern in C#

In computer programming, the specification pattern is a particular software design pattern, whereby business rules can be recombined by chaining the business rules together using boolean logic. The pattern is frequently used in the context of domain-driven design.

In short, the main benefit of using “specifications” is a possibility to have all the rules for filtering domain model objects in one place, instead of a thousand of lambda expressions spread across an application.

(more…)

CombGuid: Generation of SQL Server-friendly Guid Values in .NET Applications

Usage of UUID as a primary key for tables has a bunch of pros, including the option to retrieve IDs for objects created in a client application on its own without calls to the database server. However, usage of UUID as a primary key has a con: GUIDs generated by the client application may be not quite SQL Server-friendly that can lead to the overhead during the addition of a new record. (more…)

Comparing Objects by Value. Part 6: Structure Equality Implementation

We have already analyzed peculiarities of structs of the .NET framework that represent Value Types when comparing objects by value – instance of structs.

Now, I am going to describe this process on a particular example to check whether it will allow us to determine the use of the object comparison by value in general and thus, to simplify a sample of comparing objects by value – class instances that represent reference types.

(more…)

Comparing Objects by Value. Part 1. Beginning

It is a common fact that the .NET object model, as well as other software program platforms, allow comparing objects by reference and by value.

By default, two objects are equal if the corresponding object variables have the same reference. Otherwise, they are different.

However, in some cases, you may need to state that two objects belonging to the same class are equal if their content match in a certain way.

Assume we have the Person class, which contains some personal data – First Name, Last Name, and Birth date.

Consider the following points:

  1. What is the minimum required number of class modifications to assure comparing class objects by values with the help of the standard .NET architecture?
  2. What is the minimum required number of class modifications to assure comparing class objects by values (every time, if not explicitly stated that objects may be compared by a reference) with the help of the standard .NET architecture?

For each case, we will see the best way to compare objects by value to get a consistent, compact, copy-paste free, and productive code. It is not as trivial as it may seem for the first time.

(more…)

Sorting in .NET

Sorting is a typical task each programmer should be aware of. That’s why this article is dedicated to the implementation of sorting in .NET. I will describe how array sorting works in .NET, its aspects, and make a small comparison with sorting in Java.

Let’s begin with the fact that the first versions of .NET use the quicksort algorithm by default. So, let’s consider pros and cons of the quicksort.

Pros

  1. One of the most high-performance algorithms(on a practical level) of general-purpose internal sorting.
  2. Easy implementation.
  3. Requires just O(logn) of additional memory for its operation.
  4. Can be easily combined with caching and internal memory mechanisms.

(more…)

Aspects of Strings in .NET

The string data type is one of the most significant data types in any programming language. You can hardly write a useful program without it. Nevertheless, many developers do not know certain aspects of this type. Therefore, let’s consider these aspects.

Representation of strings in memory

In .Net, strings are located according to the BSTR (Basic string or binary string) rule. This method of string data representation is used in COM (the word ‘basic’ originates from the Visual Basic programming language in which it was initially used). As we know, PWSZ (Pointer to Wide-character String, Zero-terminated) is used in C/C++ for representation of strings. With such location in memory, a null-terminated is located in the end of a string. This terminator allows to determine the end of the string. The string length in PWSZ is limited only by a volume of free space. (more…)

StringBuilder: the Past and the Future

In the previous article, I elaborated on peculiarities of string concatenation. In this article, I would like to consider the StringBuilder class in detail.

As we all know, strings in .Net are immutable (without use of unsafe). Therefore, it is not a good idea to perform concatenation frequently. It means that the following code has quite serious problems with memory load:

So, what is wrong with this code?
(more…)