Regex, trim

Regex in C# can be used to trim whitespace. Trimming a string removes whitespace and leaves only the important contents.

Several methods for trimming strings are available, each with pluses and minuses. We trim strings using Regex in the C# programming language.

Example

One problem we might encounter is multiple-line strings. With Regex, we can indicate how we want the engine to treat newlines (\n).

using System;
using System.Text.RegularExpressions;

string source = "  Some text ";

// Part 1: use the ^ to match at the start.
// ... Then, look through all whitespace characters with \s.
// ... Use + to look through more than 1 characters.
// ... Then replace with an empty string.
source = Regex.Replace(source, @"^\s+", "");

// Part 2: trim with a $ on the end.
// ... This requires that we match at the end.
source = Regex.Replace(source, @"\s+$", "");

Console.WriteLine($"[{source}]");
[Some text]

Combined Regex

Here we look at another way you can trim strings using Regex. We combine the 2 regular expressions into one, and then use a single Regex Replace call.

using System;
using System.Text.RegularExpressions;

// Use both regular expressions at once.
string source = " cat\n";
source = Regex.Replace(source, @"^\s+|\s+$", "");
Console.WriteLine($"[{source}]");
[cat]

If you need Trim with different requirements than the built-in methods, the Regex methods will be easier. If it is reasonable to use the built-in Trim, this is preferable.

With Regex in the C# language we can trim the starts and ends of strings. For many tasks, such as processing data in the background, Regex is ideal.