9.10 Find Files That Match a Wildcard Expression

Problem

You need to process multiple files based on a filter expression (such as *.dll or mysheet20??.xls).

Solution

Use the overloaded version of the System.IO.DirectoryInfo.GetFiles method that accepts a filter expression and returns an array of FileInfo objects.

Discussion

The DirectoryInfo and Directory objects both provide a way to search the current directories for files that match a specific filter expression. These search expressions can use the standard ? and * wildcards. You can use a similar technique to retrieve directories that match a specified search pattern by using the overloaded DirectoryInfo.GetDirectories method.

For example, the following code retrieves the names of all the files in a specified directory that match a specified filter string. The directory and filter expression are submitted as command-line arguments. The code then iterates through the retrieved FileInfo collection of matching files and displays the name and size of each one.

 using System; using System.IO; public class WildcardTest {     private static void Main(string[] args) {         if (args.Length != 2) {             Console.WriteLine(               "USAGE:  WildcardTest [directory] [filterExpression]");             return;         }         DirectoryInfo dir = new DirectoryInfo(args[0]);         FileInfo[] files = dir.GetFiles(args[1]);                      // Display the name of all the files.         foreach (FileInfo file in files) {             Console.Write("Name: " + file.Name + "  ");             Console.WriteLine("Size: " + file.Length.ToString());         }         Console.ReadLine();     } } 

If you want to search subdirectories, you'll need to add your own recursion. Several of the recipes in this chapter demonstrate recursive file processing logic, including recipes 9.3 and 9.4.