Regex.Replace, digits

A C# Regex can match numeric characters. This helps with certain requirements. Some programs need to remove digit character to clean up input data.

Metacharacters

The "\d" metacharacter matches digit characters. Conversely the "\D" metacharacter matches non-digit characters. Uppercase means "not."

In this example, the characters with the exact values 0 through 9 must be removed from the string. They are not replaced with other characters but entirely removed.

using System;
using System.Text.RegularExpressions;

class Program
{
    /// <summary>
    /// Remove digits from string.
    /// </summary>
    public static string RemoveDigits(string key)
    {
        // Part 2: use Regex.Replace with a metacharacter, and replace with an empty string.
        return Regex.Replace(key, @"\d", "");
    }

    static void Main()
    {
        // Part 1: remove the digits in these example input strings.
        string input1 = "Dot123Net456Perls";
        string input2 = "101Dalmatations";
        string input3 = "4 Score";

        string value1 = RemoveDigits(input1);
        string value2 = RemoveDigits(input2);
        string value3 = RemoveDigits(input3);

        Console.WriteLine(value1);
        Console.WriteLine(value2);
        Console.WriteLine(value3);
    }
}
DotNetPerls
Dalmatations
 Score

Performance

The performance of Regex.Replace is far from ideal. For more speed, you could use a char array and dynamically build up the output string.

Summary

You can remove number characters in strings using the C# language. This requirement is common, and useful in the real world. We proved the method's correctness.