using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(?<![\p{L}0-9])([#＃][·・ー_0-9０-９a-zA-Zａ-ｚＡ-Ｚぁ-んァ-ン一-龠]{1,24})(?![\p{L}0-9])";
string input = @"Hashtag must be started with # character.
Hashtag will be detected by space character and other special characters (!,@,&,*,%,$).
Example 1: Hello#guys. This is a #test. -> Valid hashtag: #test.
Example 2: Hello#guys. This is a #test!#message. -> Valid hashtag: #test and #message
Example 3: Hello#guys. This is a #test #message. -> Valid hashtag: #test and #message
Example 4: Hello#guys. This is a #test#message. -> Valid hashtag: #test
Example 5: #asdasdasdasdasdasdasdasdasd -> Valid hashtag: none
Example 6: # -> Valid hashtag: none
#日本語#asd => Valid hashtag should be #日本語
#日本語日本語日本語日本語日本語日本語日本語日本語日本語 => Will not a valid hashtag";
RegexOptions options = RegexOptions.CultureInvariant;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx