Regex.Split, digits

Regex.Split can extract numbers from strings. We get all the numbers that are found in a string. Ideal here is the Regex.Split method with a delimiter code.

We describe an effective way to get all positive ints. For floating point numbers, or negative numbers, another solution will be needed.

Input and output

Let us first consider the input and output of our Regex.Split call. We want to extract digit sequences of 1 or more chars. This leaves us with numbers (in a string array).

ABC 4: 3XYZ 10

Results = 4
          3
         10

Example program

The const input string has 4 numbers in it: they are one or two digits long. To acquire the numbers, we use the format string "\D+" in the Regex.Split method.

using System;
using System.Text.RegularExpressions;

const string input = "ABC 4: 3XYZ 10";
// Split on one or more non-digit characters.
string[] numbers = Regex.Split(input, @"\D+");
foreach (string value in numbers)
{
    if (!string.IsNullOrEmpty(value))
    {
        int i = int.Parse(value);
        Console.WriteLine("Number: {0}", i);
    }
}
Number: 4
Number: 3
Number: 10
\D    Non-digit char.
+     1 or more of char.

Notes, pattern

For handling numbers in regular expressions, the "\d" and "\D" codes are important. The lowercase "d" means digit character. The uppercase means non-digit char.

We extracted integers inside a string. And we converted the results to ints. The Regex.Split method is useful for this purpose. It allows flexible, complex delimiters.