C# – Use yield return to minimize memory usage

Let’s say you want to search through a large text file for specific characters and return a list of context objects to the calling code for further processing (such as showing the results in the UI). One way to do that is to build the entire list at once and return it. If you don’t … Read more

C# – Save a list of strings to a file

The simplest way to save a list of strings to a file is to use File.WriteAllLines(). This creates (or overwrites) the specified file and writes each string on a new line. The resulting file looks like this: Note: Showing non-printable newline characters \r\n for clarity. Specifying the separator character What if you want to separate … Read more

C# – Remove non-alphanumeric characters from a string

The simplest way to remove non-alphanumeric characters from a string is to use regex: Note: Don’t pass in a null, otherwise you’ll get an exception. Regex is the simplest approach for solving this problem, but it’s also the slowest. If you’re concerned about the performance take a look at the performance section below. This example … Read more

C# – Convert a list to a dictionary

The simplest way to convert a list to a dictionary is to use the Linq ToDictionary() method: This loops through the list and uses the key/element selector lambdas you passed in to build the dictionary. In this article, I’ll go into details about how to use ToDictionary() and show how to deal with duplicate keys. … Read more

Comparing performance with Benchmark.NET graphs

The following graph compares the execution time of three sort implementations ran against varying input sizes (1k, 10k, 100k): This graph was generated using Benchmark.NET, which I’ll show how to use in this article. I’ll be comparing the performance of multithreaded quicksort implementations (with the non-threaded Array.Sort() as a baseline). Create console app and reference … Read more

C# – Remove a set of characters from a string

The fastest and simplest way to remove a set of characters from a string is to use StringBuilder + List<char>, like this: I compared this with three other approaches. I did 100,000 iterations with a string with 2500 characters and a list of 15 characters to remove. This StringBuilder approach is almost 2x faster than … Read more

Multithreaded quicksort in C#

One day I decided to challenge myself by trying to implement multithreaded quicksort. I wanted to see how it would compare to the built-in sort function – Array.Sort(). I came up with two algorithms that were 2-4x faster than Array.Sort(): Top-down: divide-fork-sort-merge Bottom-up: quicksort with fork-on-recursion After continuing to tinker, in attempts to further optimize, … Read more