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C# / .NET - replace first n characters in string
0 points
In this article, we would like to show you how to replace the first n characters in a string in C# / .NET.
Quick solution:
xxxxxxxxxx1
int n = 2;2
string text = "ABCD";3
string replacement = "xy";4
string result = replacement + text.Substring(n);5
6
Console.WriteLine(result); // xyCD
In this example, we will take the last n characters from the original string and add them to the end of the replacement.
xxxxxxxxxx1
using System;2
3
public class StringUtils4
{5
public static void Main(string[] args)6
{7
int n = 2;8
string text = "ABCD";9
string replacement = "xy";10
string result = replacement + text.Substring(n);11
12
Console.WriteLine(result); // xyCD13
}14
}This approach is equivalent to the above one. Instead of + operator we concatenate the strings using string.Concat() method.
xxxxxxxxxx1
using System;2
3
public class StringUtils4
{5
public static void Main(string[] args)6
{7
int n = 2;8
string text = "ABCD";9
string replacement = "xy";10
string result = string.Concat(replacement, text.Substring(n));11
12
Console.WriteLine(result); // xyCD13
}14
}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.).
xxxxxxxxxx1
using System;2
using System.Text.RegularExpressions;3
4
public class StringUtils5
{6
public static void Main(string[] args)7
{8
int n = 2;9
string text = "ABCD";10
string replacement = "xy";11
string pattern = @"^.{" + n + "}";12
13
string result = Regex.Replace(text, pattern, replacement);14
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Console.WriteLine(result); // xyCD16
}17
}Note:
Regular expressions are slower than
Substring()method.
