using System;
using System.Text .RegularExpressions ;
public class Example
{
public static void Main( )
{
string pattern = @"(?<!\S)(?:x+(?:-x+)*|\d+(?:-\d+)*)$" ;
string input = @"Isaiah Kinney 06/2021 111111
Darius Knox 10/2020 111-334-555
Leo Wiley 07/2020 122-333
Stone Walls 11/2020 2112333
John Stone 12/2021 xxx-xx-xxx" ;
RegexOptions options = RegexOptions.Multiline ;
foreach ( Match m in Regex.Matches ( input, pattern, options) )
{
Console.WriteLine ( "'{0}' found at index {1}." , m.Value , m.Index ) ;
}
}
}
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