File.ReadAllLines Regex Trim String Remove Punctuation String TrimEnd, TrimStart String Whitespace

`Trim`

The C# Trim() method eliminates leading and trailing whitespace. Often we need to remove whitespace from the beginning or ending of a string—Trim helps with this.

But Trim() is not limited to just spaces. It removes any characters specified. Its behavior changes when we pass arguments to it.

Example

Here we remove spaces from the beginning and end of a string. When we call Trim on a string, it copies the string and returns a modified version as the copy.

Step 1 We specify an input string, which (like all strings) is immutable. The original is not changed when we call Trim.

Step 2 Trim() can be used with no parameters. In this case it uses a default set of whitespace characters.

Step 3 The Console.WriteLine statement prints the copied string that has no spaces at the beginning or end.

using System;

// Step 1: input string.
string value = "  a line ";

// Step 2: call Trim instance method.
// ... This returns a new string copy.
value = value.Trim();

// Step 3: write to screen.
Console.WriteLine("TRIMMED: [{0}]", value);
TRIMMED: [a line]

Line breaks

We can remove newlines from strings with Trim. The Trim method will remove both UNIX style line breaks and Windows style line breaks.

Part 1 We have an input string, and we print it to the Console with Console.WriteLine, surrounding it with square brackets.

Part 2 We invoke Trim—it copies the input string, modifies the copy, and then returns a new copy.

using System;

// Part 1: display the input string.
string value = "This is an example string.\r\n\r\n";
Console.WriteLine("[{0}]", value);

// Part 2: trim the line breaks.
value = value.Trim();
Console.WriteLine("[{0}]", value);[This is an example string.

]
[This is an example string.]

Files

We next trim each line from a file. This works well with StreamReader or other File methods. The example here demonstrates Trim on each line in the file.

Note The file, located at path "file.txt" contains three lines, each ending with a space.

Detail The code first uses File.ReadAllLines. Then it loops through the lines using foreach.

Then Each line is trimmed. Because all the lines are in memory, the original file is not changed.

using System;
using System.IO;

foreach (string line in File.ReadAllLines("file.txt"))
{
    Console.WriteLine("[" + line + "]");
    string trimmed = line.Trim();
    Console.WriteLine("[" + trimmed + "]");
}
// In the loop we can use both strings.
// ... No string is changed: Trim() copies the strings.[This file ]
[This file]
[Has some ]
[Has some]
[Whitespace you don't want ]
[Whitespace you don't want]

Performance

I tested how Trim performs on different strings. For example, I benchmarked Trim on a string that has characters to be trimmed, against a string that doesn't need changing.

And My results were that Trim takes more time when it has more characters to remove from the source string.

Note Trim() iterates through the characters until no more trimming can be done. No numbers are available in this document.

Methods

There are other ways you will need to change or replace the whitespace in strings. For example, you may need to change whitespace in the middle of strings, not just on the end.

Punctuation is another common character type we need to trim. This can be challenging with just the Trim method—a custom array is required.

Trimming strings is commonly done—it removes leading and trailing whitespace. Trim, unlike TrimEnd and TrimStart, acts on both the start and end in a single call.