Solve real coding problems
Converting a char to an int means getting the numeric value that the char represents (i.e. ‘1’ to 1). This is not the same as casting the char to an int, which gives you the char’s underlying value (i.e. ‘1’ is 49). There are three ways to convert a char to an int: I’ll show … Read more
LinkedList<T> is a doubly linked list. It consists of nodes with values (i.e. integers, strings, etc…) and links to the next and previous node. LinkedList<T> has a reference to the head and tail nodes, which enables efficient insertion (and removal) from the start and end of the list. The main reason to use LinkedList<T> is … Read more
There are two ways to iterate through a List<T> and remove items based on a condition: These remove items from the list in an in-place manner (i.e. modify the original list) and avoid the problems you run into when doing this incorrectly (such as using a foreach or looping forward). I’ll show examples below. Then … Read more
When you need to sort a list, you don’t need to reinvent the wheel. You can use one of these three built-in methods for sorting a list: In this article, I’ll show examples of using these three approaches for sorting a list. Sort a list with OrderBy() (Linq) The OrderBy() Linq method generates an IOrderedEnumerable … Read more
StreamWriter buffers by writing data to an internal char array with a default size of 1024 (and a minimum size of 128). Once the buffer is full (or when you dispose the StreamWriter), it flushes the buffer to the underlying stream. You can change StreamWriter’s buffer size by passing in the bufferSize parameter. Here’s an … Read more
In this article, I’ll show how to parse a CSV file manually and with a parser library (CsvHelper). Let’s say you have the following CSV file: To manually parse this, read the file line by line and split each line with a comma. This gives you a string array containing the fields that you can … Read more
The simplest way to loop through a dictionary is with a foreach loop. Here’s an example of initializing a dictionary with values and then looping through it: This outputs the following: The loop variable is a KeyValuePair<string, int> with Key and Value properties. Instead of using this, you can deconstruct the KeyValuePair into named variables, … Read more
Here’s an example of deserializing JSON from a file as a stream with System.Text.Json: Stream deserialization has three main benefits: In this article, I’ll go into details about these benefits and show a few other stream serialization scenarios. Benefits of deserializing as a stream Performance There are two ways to deserialize JSON: Deserializing a stream … Read more
Let’s say you want to search for specific characters in a large text file 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
The simplest way to save a list of strings to a file is to use File.WriteAllLines(). This creates (or overwrites) the 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 each … Read more
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 options for removing characters by “category” (as opposed to removing arbitrary lists of characters or removing characters by position). The downside is that regex is the … Read more
The simplest way to get query results as JSON is to use FOR JSON PATH in the query (note: this was added in SQL Server 2016): It returns the results as a single JSON string with one JSON object per row: Note: SQL Server returns the JSON without indenting. All examples in this article show … Read more
There are three ways to select distinct objects based on a property using Linq methods: These select one movie per year: The simplest option is using GroupBy() because it doesn’t require any additional code. Distinct() is faster but it’s more complicated. DistinctBy() is the fastest and simplest, but requires the most code (it requires .NET … Read more
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
Padding a 2D array on all sides means adding new rows on the top and bottom, new columns on the left and right, and then copying the original elements to the center of the padded array. It looks like this: There are two approaches for copying the elements. You can either copy individual items in … Read more
ASP.NET Core uses System.Text.Json as the default JSON serializer. To configure the JSON serializer options, call AddJsonOptions() in the initialization code: Calling AddJsonOptions() gives you access to the global JsonSerializerOptions object. This is used for all requests / responses. You can configure the options and add converters (including your own custom JSON converters). ASP.NET Core’s … Read more
When you want to remove a list of characters from a string, loop through the list and use string.Replace(): Note that string.Replace() returns a new string (because strings are immutable). Running this outputs the following: This is the fastest approach (in .NET 6+). Linq approach: Where() + ToArray() + new string() Another option for removing … Read more
When you have a slow SELECT query, the most likely cause of the problem is that you’re missing an index. When your table has lots of data, having the right indexes will make a difference in the performance. Without indexes, SQL Server has to scan through your entire table to find the rows that match … Read more
In this article, I’ll explain how to solve the Two Strings algorithm problem on HackerRank. Problem statement: Given two strings, determine if they have a substring in common. The strings can have up to 100k characters. Example: Given “hello world” and “world”, do they have a substring in common? Yes, they many substrings in common. … Read more
This article shows code for converting a hex string to a byte array, unit tests, and a speed comparison. First, this diagram shows the algorithm for converting a hex string to a byte array. To convert a hex string to a byte array, you need to loop through the hex string and convert two characters … Read more
In this article I’ll explain how to copy an object. I’ll explain the difference between shallow and deep copying, and then show multiple ways to do both approaches for copying objects. At the end, I’ll show a performance and feature comparison to help you decide which object copying method to use. Shallow copy vs Deep … Read more
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 Array.Sort() method. I came up with two algorithms that were 2-4x faster than Array.Sort(): After continuing to tinker, in attempts to further optimize, I came across the AsParallel().OrderBy() method (PLINQ). After … Read more