Regex to match a Number between two strings [duplicate] - regex

Question

I have a string that looks like the following:
<#399969178745962506> hello to <#!104729417217032192>
I have a dictionary containing both that looks like following:
{"399969178745962506", "One"},
{"104729417217032192", "Two"}
My goal here is to replace the <#399969178745962506> into the value of that number key, which in this case would be One
Regex.Replace(arg.Content, "(?<=<)(.*?)(?=>)", m => userDic.ContainsKey(m.Value) ? userDic[m.Value] : m.Value);
My current regex is as following: (?<=<)(.*?)(?=>) which only matches everything in between < and > which would in this case leave both #399969178745962506 and #!104729417217032192
I can't just ignore the # sign, because the ! sign is not there every time. So it could be optimal to only get numbers with something like \d+
I need to figure out how to only get the numbers between < and > but I can't for the life of me figure out how.
Very grateful for any help!

Answer 1

In C#, you may use 2 approaches: a lookaround based on (since lookbehind patterns can be variable width) and a capturing group approach.
Lookaround based approach
The pattern that will easily help you get the digits in the right context is
(?<=<#!?)\d+(?=>)
See the regex demo
The (?<=<#!?) is a positive lookbehind that requires <= or <=! immediately to the left of the current location and (?=>) is a positive lookahead that requires > char immediately to the right of the current location.
Capturing approach
You may use the following pattern that will capture the digits inside the expected <...> substrings:
<#!?(\d+)>
Details
<# - a literal <# substring
!? - an optional exclamation sign
(\d+) - capturing group 1 that matches one or more digits
> - a literal > sign.
Note that the values you need can be accessed via match.Groups[1].Value as shown in the snippet above.
Usage:
var userDic = new Dictionary<string, string> {
{"399969178745962506", "One"},
{"104729417217032192", "Two"}
};
var p = #"<#!?(\d+)>";
var s = "<#399969178745962506> hello to <#!104729417217032192>";
Console.WriteLine(
Regex.Replace(s, p, m => userDic.ContainsKey(m.Groups[1].Value) ?
userDic[m.Groups[1].Value] : m.Value
)
); // => One hello to Two
// Or, if you need to keep <#, <#! and >
Console.WriteLine(
Regex.Replace(s, #"(<#!?)(\d+)>", m => userDic.ContainsKey(m.Groups[2].Value) ?
$"{m.Groups[1].Value}{userDic[m.Groups[2].Value]}>" : m.Value
)
); // => <#One> hello to <#!Two>
See the C# demo.

Answer 2

To extract just the numbers from you're given format, use this regex pattern:
(?<=<#|<#!)(\d+)(?=>)
See it work in action: https://regexr.com/3j6ia

Answer 3

You can use non-capturing groups to exclude parts of the needed pattern to be inside the group:
(?<=<)(?:#?!?)(.*?)(?=>)
alternativly you could name the inner group and use the named group to get it:
(?<=<)(?:#?!?)(?<yourgroupname>.*?)(?=>)
Access it via m.Groups["yourgroupname"].Value - more see f.e. How do I access named capturing groups in a .NET Regex?

Answer 4

Regex: (?:<#!?(\d+)>)
Details:
(?:) Non-capturing group
<# matches the characters <# literally
? Matches between zero and one times
(\d+) 1st Capturing Group \d+ matches a digit (equal to [0-9])
Regex demo
string text = "<#399969178745962506> hello to <#!104729417217032192>";
Dictionary<string, string> list = new Dictionary<string, string>() { { "399969178745962506", "One" }, { "104729417217032192", "Two" } };
text = Regex.Replace(text, #"(?:<#!?(\d+)>)", m => list.ContainsKey(m.Groups[1].Value) ? list[m.Groups[1].Value] : m.Value);
Console.WriteLine(text); \\ One hello to Two
Console.ReadLine();