C# – Pad a 2D array on all sides

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

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

C# – Convert a list of strings into a set of enums

Let’s say you have a list of HTTP status codes that you read in when the service starts up (perhaps from appsettings.json or from the database). Whenever you send an HTTP request, you want to check if the returned status code is in this list of status code. To make things more efficient, you want … Read more

C# – IPv4 range validation

Given a starting IPv4 address and an ending IPv4 address, how do you know if this is a valid range? The range is valid if: The starting IPv4 address is valid. The ending IPv4 address is valid. The range is a class C network with subnet mask 255.255.255.0. This means the starting IP and ending … Read more

Set Operations – Intersect, Union, Difference, and Symmetric Difference

In the show House, different sets of main characters appeared in different seasons. For example, here are the main characters that starred in seasons 1 and 7: Characters in Season 1 Characters in Season 7 HouseCuddyWilsonForemanChaseCameron HouseCuddyWilsonForemanChaseTaubThirteenMasters Set operations allow you to answer interesting questions, such as “Which House main characters appeared in both seasons … Read more

C# – Merge two dictionaries in-place

When you merge two dictionaries, you can either merge them in-place, or create a new dictionary and copy the values over to it. The following extension method does an in-place merge of two dictionaries. It puts items from the right dictionary into the left dictionary. When duplicate keys exist, it’s keeping the value from the … Read more

C# – Hex string to byte array

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