Remove specific characters from a string in C#

Given a set of characters, remove those characters from a string in C#.

It is common knowledge that string is immutable in C#, i.e., we cannot change the contents of a string object; we can change only the reference to the object. Therefore, to remove any characters from a string, we need to create its new instance. This post provides an overview of several methods to accomplish this:

1. Using `String.Replace()` method

A fairly simple solution is to use the String.Replace() method for replacing all occurrences of specified characters in the current string. This is demonstrated below:

using System;

using System.Collections.Generic;

public static class Extensions

{

public static string Filter(this string str, List<char> charsToRemove)

{

foreach (char c in charsToRemove) {

str = str.Replace(c.ToString(), String.Empty);

}

return str;

}

public class Example

{

public static void Main()

{

string str = "@Hello, World.";

List<char> charsToRemove = new List<char>() { '@' ,'_', ',' ,'.' };

str = str.Filter(charsToRemove);

Console.WriteLine(str);

}

Output: Hello World

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We can also use the List.ForEach() method in place of the foreach loop, as shown below:

using System;

using System.Collections.Generic;

public static class Extensions

{

public static string Filter(this string str, List<char> charsToRemove)

{

charsToRemove.ForEach(c => str = str.Replace(c.ToString(), String.Empty));

return str;

}

public class Example

{

public static void Main()

{

string str = "@Hello, World.";

List<char> charsToRemove = new List<char>() { '@' ,'_', ',' ,'.' };

str = str.Filter(charsToRemove);

Console.WriteLine(str);

}

Output: Hello World

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2. Using `String.Split()` method

The idea is to split the string with given characters. This can be easily done using the String.Split() method, as demonstrated below:

using System;

using System.Collections.Generic;

public static class Extensions

{

public static string Filter(this string str, List<char> charsToRemove)

{

// return String.Join(String.Empty, str.Split(charsToRemove.ToArray()));

return String.Concat(str.Split(charsToRemove.ToArray()));

}

public class Example

{

public static void Main()

{

string str = "@Hello, World.";

List<char> charsToRemove = new List<char>() { '@', '_', ',', '.' };

str = str.Filter(charsToRemove);

Console.WriteLine(str);

}

Output: Hello World

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3. Regular Expressions

We can use regular expressions to remove specific characters in a string. The idea is to check for specific characters in a string and replace them with an empty string. The following code example shows how to implement this. Note below implementation will fail for characters that need escaping.

using System;

using System.Text.RegularExpressions;

using System.Collections.Generic;

public static class Extensions

{

public static string Filter(this string str, List<char> charsToRemove)

{

String chars = "[" + String.Concat(charsToRemove) + "]";

return Regex.Replace(str, chars, String.Empty);

}

public class Example

{

public static void Main()

{

string str = "@Hello, World.";

List<char> charsToRemove = new List<char>() { '@' ,'_', ',' ,'.' };

str = str.Filter(charsToRemove);

Console.WriteLine(str);

}

Output: Hello World

Download Run Code

That’s all about removing specific characters from a string in C#.

Remove specific characters from a string in C#

1. Using String.Replace() method

2. Using String.Split() method

3. Regular Expressions

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1. Using `String.Replace()` method

2. Using `String.Split()` method