How to detect number between underscore ("_")?

Question

Sorry first, im not good at Regex but anyone can help me ? i have file that named :

Filename - 01.exe

Filename - 001.exe

Filename - 0001.exe

Filename_01_.exe

I have tried with this Regex

(?=.*?)\d{1,4}\b

But that just detect 01, 001, 0001 number at Filename - 01.exe, Filename - 001.exe and Filename - 0001.exe, not worked with Filename_01_.exe Is my Regex is wrong or there Alternative Regex or Method ?

Sorry if my english is not well.

Answer 1

Since there is only one number in the file, how about simply using this:

\d+

In C#:

var myRegex = new Regex(@"\d+");
string resultString = myRegex.Match(yourString).Value;
Console.WriteLine(resultString);