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

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

Quick solution: 

int n = 2;
string originalString = "ABCD";

string replaced = originalString.Substring(0, originalString.Length - n) + "12";

Console.WriteLine(originalString); // ABCD
Console.WriteLine(replaced);       // AB12

Practical examples

1. Using Substring() method

using System;

public class Program
{
    static string ReplaceLastLetters(string text, int letterCount, string newLetters)
    {
        string substring = text.Substring(0, text.Length - letterCount); // ABCD -> AB
        return substring + newLetters;
    }

    public static void Main(string[] args)
    {
        int n = 2;
        string originalString = "ABCD";
        string newLetters = "12";

        string replaced = ReplaceLastLetters(originalString, n, newLetters);

        Console.WriteLine(originalString); // ABCD
        Console.WriteLine(replaced);       // AB12
    }
}

Output:

ABCD
AB12

1. Using Remove() method

using System;

public class Program
{
    static string ReplaceLastLetters(string text, int letterCount, string newLetters)
    {
        string substring = text.Remove(text.Length - letterCount, letterCount); // ABCD -> AB
        return substring + newLetters;
    }

    public static void Main(string[] args)
    {
        int n = 2;
        string originalString = "ABCD";
        string newLetters = "12";

        string replaced = ReplaceLastLetters(originalString, n, newLetters);

        Console.WriteLine(originalString); // ABCD
        Console.WriteLine(replaced);       // AB12
    }
}

Output:

ABCD
AB12

 References

1. String Substring() - .NET Docs