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How to find and extract a number from a string in C#?
A regular expression is a pattern that could be matched against an input text. The .Net framework provides a regular expression engine that allows such matching. A pattern consists of one or more character literals, operators, or constructs.
Here are basic pattern metacharacters used by RegEx −
* = zero or more ? = zero or one ^ = not [] = range
The ^ symbol is used to specify not condition.
the [] brackets if we are to give range values such as 0 - 9 or a-z or A-Z
Using Char.IsDigit()
Example
using System;
namespace DemoApplication{
public class Program{
static void Main(string[] args){
string str1 = "123string456";
string str2 = string.Empty;
int val = 0;
Console.WriteLine($"String with number: {str1}");
for (int i = 0; i < str1.Length; i++){
if (Char.IsDigit(str1[i]))
str2 += str1[i];
}
if (str2.Length > 0)
val = int.Parse(str2);
Console.WriteLine($"Extracted Number: {val}");
Console.ReadLine();
}
}
}Output
String with number: 123string456 Extracted Number: 123456
In the above example we are looping all the characters of the string str1. The Char.IsDigit() validates whether the particular character is a number or not and adds it to a new string which is later parsed to a numer.
Using Regex
Example
using System;
using System.Text.RegularExpressions;
namespace DemoApplication{
public class Program{
static void Main(string[] args){
string str1 = "123string456";
string str2 = string.Empty;
int val = 0;
Console.WriteLine($"String with number: {str1}");
var matches = Regex.Matches(str1, @"\d+");
foreach(var match in matches){
str2 += match;
}
val = int.Parse(str2);
Console.WriteLine($"Extracted Number: {val}");
Console.ReadLine();
}
}
}Output
String with number: 123string456 Extracted Number: 123456
In the above example, we use the regular expression (\d+) to extract only the numbers from the string str1.
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