我认为我在 C# 中的正则表达式模式不正确

Question

I'm checking to see if my regular expression matches my string. I have a filename that looks like somename_somthing.txt and I want to match it to somename_*.txt , but my code is failing when I try to pass something that should match. Here is my code.

string pattern = "somename_*.txt";
Regex r = new Regex(pattern, RegexOptions.IgnoreCase);
using (ZipFile zipFile = ZipFile.Read(fullPath))
{
   foreach (ZipEntry e in zipFile)
   {
       Match m = r.Match("somename_something.txt");
       if (!m.Success)
       {
           throw new FileNotFoundException("A filename with format: " + pattern + " not found.");
        }
    }
}

Answer 1

In General

Regex give in this code matches the _ with an * meaning zero or more underscores instead of what you intended. The * is used to denote zero or more of the previous item. Instead try

^somename_(.*)\.txt$

This matches exactly the first part "somename_".

Then anything (.*)

And finally the end ".txt". The backslash escapes the 'dot'.

More Specific

You can also say if you only want letters and not numbers or symbols in the middle part of the match with:

^somename_[a-z]*\.txt$

Answer 2

The asterisk is matching the underscore and throwing it off.

Try:

somename_(\w+).txt

The (\\w+) here will match the group at this location.

You can see it match here: https://regex101.com/r/qS8wA5/1

Answer 3

As written, your regular expression

somename_*.txt

matches (in a case-insensitive manner):

• the literal text somename , followed by
• zero or more underscore characters ( _ ), followed
• any character (other than newline), followed
• the literal text txt

And it will match that anywhere in the source text. You probably want to write something like

Regex myPattern = new Regex( @"
    ^        # anchor the match to start-of-text, followed by
    somename # the literal 'somename', followed by
    _        # a literal underscore character, followed by
    .*       # zero or of any character (except newline), followed by
    \.       # a literal period/fullstop, followed by
    txt      # the literal text 'txt' 
    $        # with the match anchored at end-of-text
  " , RegexOptions.IgnoreCase|RegexOptions.IgnorePatternWhitespace
  ) ;

Answer 4

Hi I think the pattern should be

string pattern = "somename_.*\\.txt";

Regards