C# Regex will not match

Question

Attempting to write code that will pick up all of a month's log files and zip them up. I can't see to get the RegEx pattern to work in my code. Below is a sandbox console app I'm using to test with:

public static void Main(string[] args)
{
    var targetDate = DateTime.Now.AddMonths(-1);
    var pattern = $@"c:\\logs\\client-{targetDate.Year}-{targetDate.Month:d2}-.*.log";
    Regex regex = new Regex(Regex.Escape(pattern), RegexOptions.IgnoreCase);
    var files = Directory.EnumerateFiles(@"c:\logs").Where(f => regex.IsMatch(f)).ToList();
    
    foreach(var file in files)
    {
        Console.WriteLine(file);
    }
}

The Enumerated files look like the following:

c:\logs\client-2021-03-01.log
c:\logs\client-2021-03-02.log
c:\logs\client-2021-03-03.log
c:\logs\client-2021-03-04.log
c:\logs\client-2021-03-05.log
c:\logs\client-2021-03-06.log
c:\logs\client-2021-03-07.log
c:\logs\client-2021-03-08.log
c:\logs\client-2021-03-09.log
c:\logs\client-2021-03-10.log
c:\logs\client-2021-03-11.log
c:\logs\client-2021-03-12.log
c:\logs\client-2021-03-13.log
c:\logs\client-2021-03-14.log
c:\logs\client-2021-03-15.log
c:\logs\client-2021-03-16.log
c:\logs\client-2021-03-17.log
c:\logs\client-2021-03-18.log
c:\logs\client-2021-03-19.log
c:\logs\client-2021-03-20.log
c:\logs\client-2021-03-21.log
c:\logs\client-2021-03-22.log
c:\logs\client-2021-03-23.log
c:\logs\client-2021-03-24.log
c:\logs\client-2021-03-25.log
c:\logs\client-2021-03-26.log
c:\logs\client-2021-03-27.log
c:\logs\client-2021-03-28.log
c:\logs\client-2021-03-29.log
c:\logs\client-2021-03-30.log
c:\logs\client-2021-03-31.log
c:\logs\client-2021-04-01.log
c:\logs\client-2021-04-02.log
c:\logs\client-2021-04-03.log
c:\logs\client-2021-04-05.log
c:\logs\client-2021-04-06.log
c:\logs\client-2021-04-07.log
c:\logs\client-2021-04-08.log
c:\logs\client-2021-04-09.log
c:\logs\client-2021-04-10.log
c:\logs\client-2021-04-12.log
c:\logs\client-2021-04-13.log
c:\logs\client-2021-04-14.log
c:\logs\client-2021-04-15.log
c:\logs\client-2021-04-16.log
c:\logs\client-2021-04-17.log
c:\logs\client-2021-04-18.log
c:\logs\client-2021-04-19.log
c:\logs\client-2021-04-20.log
c:\logs\client-2021-04-21.log
c:\logs\client-2021-04-22.log
c:\logs\client-2021-04-23.log
c:\logs\client-2021-04-24.log
c:\logs\client-2021-04-25.log
c:\logs\client-2021-04-26.log
c:\logs\client-2021-04-27.log

I've checked the RegEx pattern against a couple of testers, including one for .NET and it passes so I'm not sure where the discrepancy is. Any help would be greatly appreciated.

Answer 1

The way you escape your pattern is breaking the RegEx. Here's an example of how you can do it:

var source = @"c:\logs\client-2021-03-01.log";
var pattern = $@"c:\\logs\\client-2021-03-.*.log";

var regex = new Regex(pattern, RegexOptions.IgnoreCase);

var match = regex.Match(source); // This is now true