C# Regex – How to get substring from between "_" and "\r\n"

December 22, 2023

In example string:
string input = "8240617_8240608_8240573\r\n";
i need to get only the last part: 8240573.
In finale application there can be dots and letters. But it will always be end of the line and between "_" and "\r\n".

I tried code below but whit no result 🙁

string input = "8240617_8240608_8240573\r\n";
string pattern = @"-(.*?)\\r\\n";

Match match = Regex.Match(input, pattern);
if (match.Success)
{
    string extractedString = match.Groups[1].Value;
    Debug.WriteLine("Extracted substring: " + extractedString);
}
else
{
    Debug.WriteLine("Substring not found.");
}

>Solution :

Your regex pattern is off. Use this version (and keep the rest of the code the same):

string pattern = @"([^_]+)\r\n";

This regex says to match:

([^_]+) match the last underscore separated term
\r\n followed by CRLF

Note that in your version you were matching a hyphen, and also it would have picked up across multiple terms. Also, a newline inside an @ string in C# is @"\n", with just a single backslash.