using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^[\s\S]*(?:^|\r?\n)\s+(\d+)(?![\s\S]*(\r?\n){2})";
string input = @"this is test
1. this is test
2. this is test
3. this is test
this is test
1. this test
2. this is test 5
this is test";
RegexOptions options = RegexOptions.Multiline;
Match m = Regex.Match(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