How do I check if a filename matches a wildcard pattern

Question

I\'ve got a wildcard pattern, perhaps \"*.txt\" or \"POS??.dat\".

I also have list of filenames in memory that I need to compare to that pattern.

How would

Answer 1

Some kind of regex/glob is the way to go, but there are some subtleties; your question indicates you want identical semantics to IO.DirectoryInfo.GetFiles. That could be a challenge, because of the special cases involving 8.3 vs. long file names and the like. The whole story is on MSDN.

If you don't need an exact behavioral match, there are a couple of good SO questions:

glob pattern matching in .NET
How to implement glob in C#

Answer 2

The use of RegexOptions.IgnoreCase will fix it.

public class WildcardPattern : Regex {
    public WildcardPattern(string wildCardPattern)
        : base(ConvertPatternToRegex(wildCardPattern), RegexOptions.IgnoreCase) {
    }

    public WildcardPattern(string wildcardPattern, RegexOptions regexOptions)
        : base(ConvertPatternToRegex(wildcardPattern), regexOptions) {
    }

    private static string ConvertPatternToRegex(string wildcardPattern) {
        string patternWithWildcards = Regex.Escape(wildcardPattern).Replace("\\*", ".*");
        patternWithWildcards = string.Concat("^", patternWithWildcards.Replace("\\?", "."), "$");
        return patternWithWildcards;
    }
}

Answer 3

You could translate the wildcards into a regular expression:

*.txt -> ^.+\.txt$

POS??.dat _> ^POS..\.dat$

Use the Regex.Escape method to escape the characters that are not wildcars into literal strings for the pattern (e.g. converting ".txt" to "\.txt").

The wildcard * translates into .+, and ? translates into .

Put ^ at the beginning of the pattern to match the beginning of the string, and $ at the end to match the end of the string.

Now you can use the Regex.IsMatch method to check if a file name matches the pattern.

Answer 4

You can simply do this. You do not need regular expressions.

using Microsoft.VisualBasic.CompilerServices;

if (Operators.LikeString("pos123.txt", "pos?23.*", CompareMethod.Text))
{
  Console.WriteLine("Filename matches pattern");
}

Or, in VB.Net,

If "pos123.txt" Like "pos?23.*" Then
  Console.WriteLine("Filename matches pattern")
End If

In c# you could simulate this with an extension method. It wouldn't be exactly like VB Like, but it would be like...very cool.

Answer 5

For anyone who comes across this question now that it is years later, I found over at the MSDN social boards that the GetFiles() method will accept * and ? wildcard characters in the searchPattern parameter. (At least in .Net 3.5, 4.0, and 4.5)

Directory.GetFiles(string path, string searchPattern)

http://msdn.microsoft.com/en-us/library/wz42302f.aspx

Answer 6

Plz try the below code.

static void Main(string[] args)
    {
        string _wildCardPattern = "*.txt";

        List<string> _fileNames = new List<string>();
        _fileNames.Add("text_file.txt");
        _fileNames.Add("csv_file.csv");

        Console.WriteLine("\nFilenames that matches [{0}] pattern are : ", _wildCardPattern);
        foreach (string _fileName in _fileNames)
        {
            CustomWildCardPattern _patetrn = new CustomWildCardPattern(_wildCardPattern);
            if (_patetrn.IsMatch(_fileName))
            {
                Console.WriteLine("{0}", _fileName);
            }
        }

    }

public class CustomWildCardPattern : Regex
{
    public CustomWildCardPattern(string wildCardPattern)
        : base(WildcardPatternToRegex(wildCardPattern))
    {
    }

    public CustomWildCardPattern(string wildcardPattern, RegexOptions regexOptions)
        : base(WildcardPatternToRegex(wildcardPattern), regexOptions)
    {
    }

    private static string WildcardPatternToRegex(string wildcardPattern)
    {
        string patternWithWildcards = "^" + Regex.Escape(wildcardPattern).Replace("\\*", ".*");
        patternWithWildcards = patternWithWildcards.Replace("\\?", ".") + "$";
        return patternWithWildcards;
    }
}