Languages
[Edit]
EN

C# / .NET - replace first n characters in string

0 points
Created by:
Elleanor-Williamson
260

In this article, we would like to show you how to replace the first n characters in a string in C# / .NET.

Quick solution:

int n = 2;
string text = "ABCD";
string replacement = "xy";
string result = replacement + text.Substring(n);

Console.WriteLine(result);  // xyCD

 

1. Practical examples

1.1 With + and range operator

In this example, we will take the last n characters from the original string and add them to the end of the replacement.

using System;

public class StringUtils
{
    public static void Main(string[] args)
    {
        int n = 2;
        string text = "ABCD";
        string replacement = "xy";
        string result = replacement + text.Substring(n);

        Console.WriteLine(result);  // xyCD
    }
}

1.2 With string.Concat() method and range operator

This approach is equivalent to the above one. Instead of + operator we concatenate the strings using string.Concat() method.

using System;

public class StringUtils
{
    public static void Main(string[] args)
    {
        int n = 2;
        string text = "ABCD";
        string replacement = "xy";
        string result = string.Concat(replacement, text.Substring(n));

        Console.WriteLine(result);  // xyCD
    }
}

2. Practical example using string Regex.Replace() with regex pattern

In this example, we use Regex.Replace() with "^.{n}" regex to replace the first 2 characters in the text string.

Regex explanation:

  • ^ - matches the beginning of the string,
  • . - matches any character except linebreaks,
  • {n} - matches the specified quantity of the previous token (in our case the¬†.).
using System;
using System.Text.RegularExpressions;

public class StringUtils
{
    public static void Main(string[] args)
    {
        int n = 2;
        string text = "ABCD";
        string replacement = "xy";
        string pattern = @"^.{" + n + "}";

        string result = Regex.Replace(text, pattern, replacement);

        Console.WriteLine(result);  // xyCD
    }
}

Note:

Regular expressions are slower than Substring() method.

Donate to Dirask
Our content is created by volunteers - like Wikipedia. If you think, the things we do are good, donate us. Thanks!
Join to our subscribers to be up to date with content, news and offers.
Native Advertising
ūüöÄ
Get your tech brand or product in front of software developers.
For more information Contact us
Dirask - we help you to
solve coding problems.
Ask question.

‚̧ԳŹūüíĽ ūüôā

Join