using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^(.{20})[^.]{4,}(.*)$";
string input = @"1.1234567890.ab
2.123456789012345678901.ab
3.1234567890123456789012.ab
4.12345678901234567890123.ab
5.123456789012345678901234.ab
6.1234567890123456789012345.ab
7.12345678901234567890123456.ab
8.123456789012345678901234567890.ab
9.123456789012345678901234567890.1234567890123456.7890.ab
0.123456789012345678901234567890.12345678901.234567890....abcdef012345
12345678901234567890123456789012345678901234567890";
RegexOptions options = RegexOptions.Multiline | RegexOptions.IgnoreCase;
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