The “GetFiles” function, returns all files in the given folder, including subfolders, that match the “includeMask”. The result is sorted by the file CreationTime. The function excludes all files that match the “excludeMask”

To call the function:

List<FileInfo> files = FileSystemHelper.GetFiles(@"C:\Windows","*.*", "*.exe", SortOrder.Ascending, SearchOption.AllDirectories);

The function:
/// <summary>
/// Get files in a folder sorted by creation datetime and filtered by include mask and exclude mask
/// </summary>
/// <param name=”folder”>The folder containing the files</param>
/// <param name=”includeMask”>Include files that meet the given mask</param>
/// <param name=”excludeMask”>Exclude files that meet the given mask</param>
/// <param name=”sortOrder”>Sort order, ascending or descending</param>
/// <param name=”searchOption”>AllDirectories or TopDirectoryOnly</param>
/// <returns></returns>
public staticList<FileInfo> GetFiles(string folder, string includeMask, string excludeMask, SortOrder sortOrder, SearchOption searchOption)
{
    DirectoryInfo folderDirectoryInfo = newDirectoryInfo(folder);
    List<FileInfo> files = newList<FileInfo>(folderDirectoryInfo.GetFiles(includeMask, searchOption));
   
    stringexcludeMaskRegEx = FileSystemHelper.WildcardToRegex(excludeMask);

    // exclude files
   files = (fromfile infiles
             where!Regex.IsMatch(file.Name, excludeMaskRegEx)
             selectfile).ToList<FileInfo>();

    if(files.Count > 0)
    {
        switch(sortOrder)
        {
            caseSortOrder.Ascending:
                // Sort files oldest first
               files.Sort(
                    delegate(FileInfo firstFile, FileInfo secondFile)
                    {
                        returnfirstFile.CreationTime.CompareTo(secondFile.CreationTime);
                    }
                );
                break;
            caseSortOrder.Descending:
                // Sort files newest first
               files.Sort(
                    delegate(FileInfo firstFile, FileInfo secondFile)
                    {
                        returnsecondFile.CreationTime.CompareTo(firstFile.CreationTime);
                    }
                );
                break;
        }

    }

    returnfiles;
}

/// <summary>
/// Convert a wildcard mask to regular expression
/// </summary>
/// <param name="pattern">wildcard string</param>
/// <returns>Regular expression string</returns>
public static string WildcardToRegex(string pattern)
{
    return string.Format("^{0}$", Regex.Escape(pattern).Replace("\\*", ".*").Replace("\\?", "."));
}

public enum SortOrder
{
        Ascending,
        Descending
}