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C# / .NET - replace first 3 characters in string
0 points
In this article, we would like to show you how to replace the first 3 characters in a string in C# / .NET.
Quick solution:
xxxxxxxxxx1
string text = "ABCD";2
string replacement = "xyz";3
string result = replacement + text.Substring(3);4
5
Console.WriteLine(result); // xyzD
In this example, we will take the last 3 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
string text = "ABCD";8
string replacement = "xyz";9
string result = replacement + text.Substring(3);10
11
Console.WriteLine(result); // xyzD12
}13
}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
string text = "ABCD";8
string replacement = "xyz";9
string result = string.Concat(replacement, text.Substring(3));10
11
Console.WriteLine(result); // xyzD12
}13
}In this example, we use Regex.Replace() with "^.{3}" regex to replace the first 3 characters in the text string.
Regex explanation:
^- matches the beginning of the string,.- matches any character except linebreaks,{3}- 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
string text = "ABCD";9
string replacement = "xyz";10
string pattern = @"^.{3}";11
string result = Regex.Replace(text, pattern, replacement);12
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Console.WriteLine(result); // xyzD14
}15
}Note:
Regular expressions are slower than
Substring()method.
