Remove chars

In C# programs, characters can be removed from strings. A char could be at a specific index or must be searched for first.

In .NET, we have the Remove() method on the string type. Even though it accepts string arguments, this method can help with removing characters.

Example

Remove() accepts 2 parameters. The parameters specify the index at which you want to start removing characters, and then the number of characters to remove.

using System;

// Remove the second character from the string.
// ... This character has the index of 1.
const string value1 = "ABC ABC";
string result1 = value1.Remove(1, 1);

// Find and remove the first uppercase A from the string.
// ... This character can occur at any index.
const string value2 = "ABC ABC";
string result2 = value2;
int index1 = value2.IndexOf('A');
if (index1 != -1)
{
    result2 = value2.Remove(index1, 1);
}

Console.WriteLine(result1);
Console.WriteLine(result2);
AC ABC
BC ABC

Benchmark, char removal

Chars can be removed by value. This can be done with a custom loop method or with the string Replace method.

using System;
using System.Diagnostics;

class Program
{
    static string RemoveQuotes1(string input)
    {
        int index = 0;
        char[] result = new char[input.Length];
        for (int i = 0; i < input.Length; i++)
        {
            if (input[i] != '"')
            {
                result[index++] = input[i];
            }
        }
        return new string(result, 0, index);
    }

    static string RemoveQuotes2(string input)
    {
        return input.Replace("\"", "");
    }

    const int _max = 1000000;
    static void Main()
    {
        var s1 = Stopwatch.StartNew();
        // Version 1: optimized method.
        for (int i = 0; i < _max; i++)
        {
            RemoveQuotes1("Thanks for \"visiting\"!");
        }
        s1.Stop();
        var s2 = Stopwatch.StartNew();
        // Version 2: replace call.
        for (int i = 0; i < _max; i++)
        {
            RemoveQuotes2("Thanks for \"visiting\"!");
        }
        s2.Stop();
        Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
        Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
    }
}
40.66 ns
72.67 ns

Replace chars

Replace() has an overload that accepts 2 char parameters. You cannot replace all chars of one value with an empty char with this method.

Note, substring

Let's review Substring and Remove. In this example, you could use Substring instead of Remove with no functional difference.

Char arrays

Char arrays are one of the best string manipulation optimizations you can use. They often reduce memory allocations and reduce instructions due to less copying.

We removed a specific character from a string. You can use this code to remove either a character at any index. The code uses Remove, Substring (internally), and IndexOf.