Solve real coding problems
Articles about building, parsing, searching, formatting, and converting strings in C#. The string type holds text values (i.e. “hello world”).
By default, string.Contains() does a case sensitive search for a substring (or character) in a string. You can make it do a case insensitive search instead by passing in StringComparison.OrdinalIgnoreCase, like this: Note: StringComparison has three ‘ignore case’ options to choose from. Because this is doing a case insensitive search, it matched “earth” to “Earth” … Read more
There are three methods you can use to find a character in a string: I’ll show examples below. Using string.IndexOf() to find a character string.IndexOf() returns the index of the first occurrence of a character in a string. It searches the string from left to right, starting at the beginning. If it doesn’t find the … Read more
The simplest way to remove spaces from a string is by using string.Replace(). Here’s an example: This outputs the following. Notice the spaces are removed. string.Replace() is good for removing all occurrences of a specific character (” ” in this case). When you want to remove all whitespace characters (spaces, tabs, newlines, etc..), there are … Read more
Use string.Remove() to remove character(s) from a string based on their index, such as the first or last character. This method has two parameters: string.Remove() returns a new string with the characters removed. I’ll show examples below. Remove the first character from a string To remove the first character, use string.Remove(startIndex: 0, count: 1), like … Read more
There are three ways to convert a string to an int: I’ll show examples of using these approaches. Use int.Parse() int.Parse() takes a string and converts it to a 32-bit integer. Here’s an example of using int.Parse(): When conversion fails int.Parse() throws an exception if it can’t convert the string to an int. There are … Read more
You can use String.Join() to convert a collection of items to a string with a separator (such as a comma). Here’s an example of using String.Join() to convert a List of strings to a comma-separated string: This results in the following comma-separated string: String.Join() can be used on wide variety of input: I’ll show a … Read more
There are two good ways to convert a List<T> to a string: I’ll show examples of both approaches. Using String.Join() String.Join() is the simplest way to convert a List to a string. With this method, you pass in the List and a delimiter and it outputs a string. You can use any delimiter you want. … Read more
You can convert a list of strings to a list of integers by using int.Parse() on all of the strings. There are two simple ways to do this: I’ll show examples of these using these methods and then explain how to handle parsing exceptions. Option 1 – Use List.ConvertAll() Here’s an example of how to … Read more
Let’s say you want to parse a comma-separated string into a list of integers. For example, you have “1,2,3” and you want to parse it into [1,2,3]. This is different from parsing CSV with rows of comma-separated values. This is more straightforward. You can use string.Split(“,”) to get the individual values and then convert them … 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 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
Here’s the simplest way to efficiently trim a UTF-8 string to the specified number of bytes: A UTF-8 string can have a mix of characters between 1 to 4 bytes. When you only take part of the byte array, you may end up cutting multi-byte chars in half, which then get replaced with the replacement … Read more
There are many different scenarios where you might want to check a string against a list of substrings. Perhaps you’re dealing with messy exception handling and have to compare the exception message against a list of known error messages to determine if the error is transient or not. When you need to check a string … Read more
Normally when you want to join strings using a separator, you’d use string.Join(). However, the problem with string.Join() is it doesn’t ignore nulls or empty strings. Take a look at the following examples: If you want to filter out nulls and empty strings, you can filter the list of strings yourself and pass it into … 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
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
Interpolated strings have the following structure: {variable:format}. Typically you exclude the format, so they normally look like this: $”My name is {name}”. Here’s how to use format strings with an interpolated string: This outputs the following: This is the equivalent of using string.Format() like this: As you can see, specifying a format string with an … Read more
Using string.Format() is error prone and can lead to runtime exceptions. Using string interpolation prevents these problems (and it’s more readable). This article shows the two common mistakes you can make when using string.Format(), resulting in runtime exceptions, and shows how you can use string interpolation to prevent these problems. 1 – FormatException: Format string … 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
You can use Convert.ChangeType() to convert from a string to any type, like this: Normally you’d call the specific type converter method, like Convert.ToBoolean(“true”). However, sometimes it makes sense to use the generalized type converter method – Convert.ChangeType() – instead of hardcoding the calls to specific type converter methods. I’ll show an example of when … Read more
In regex, capturing groups give you a way to save text and refer to it later. Capturing groups can be named, and referred to by their name. When they aren’t named, you refer to them by their index number. In this article, I’ll show how to use named capturing groups by solving the problem of … Read more
I’ll show how to parse comma-separated integer values from app.config and load them into a HashSet for efficient lookups. First, take a look at the setting (retryStatusCodes) in app.config: To load and parse this setting from app.config, do the following: The following code shows how to do this: Note: You have to add a reference … Read more
