此示例演示如何使用 Regex 类在文本字符串中为更复杂的匹配创建正则表达式。 通过 LINQ 查询可以轻松地准确筛选要用正则表达式搜索的文件,并对结果进行改良。

Imports System.IO
Imports System.Text.RegularExpressions
Class LinqRegExVB
    Shared Sub Main()
        ' Root folder to query, along with all subfolders.
        ' Modify this path as necessary so that it accesses your Visual Studio folder.
        Dim startFolder As String = "C:\Program Files (x86)\Microsoft Visual Studio 14.0\"
        ' One of the following paths may be more appropriate on your computer.
        'Dim startFolder As String = "C:\Program Files (x86)\Microsoft Visual Studio\2017\"
        ' Take a snapshot of the file system.
        Dim fileList As IEnumerable(Of FileInfo) = GetFiles(startFolder)
        ' Create a regular expression to find all things "Visual".
        Dim searchTerm As New Regex("Visual (Basic|C#|C\+\+|Studio)")
        ' Search the contents of each .htm file.
        ' Remove the where clause to find even more matches!
        ' This query produces a list of files where a match
        ' was found, and a list of the matches in that file.
        ' Note: Explicit typing of "Match" in select clause.
        ' This is required because MatchCollection is not a
        ' generic IEnumerable collection.
        Dim queryMatchingFiles = From afile In fileList
                                Where afile.Extension = ".htm"
                                Let fileText = File.ReadAllText(afile.FullName)
                                Let matches = searchTerm.Matches(fileText)
                                Where (matches.Count > 0)
                                Select Name = afile.FullName,
                                       Matches = From match As Match In matches
                                                 Select match.Value
        ' Execute the query.
        Console.WriteLine("The term " & searchTerm.ToString() & " was found in:")
        For Each fileMatches In queryMatchingFiles
            ' Trim the path a bit, then write
            ' the file name in which a match was found.
            Dim s = fileMatches.Name.Substring(startFolder.Length - 1)
            Console.WriteLine(s)
            ' For this file, write out all the matching strings
            For Each match In fileMatches.Matches
                Console.WriteLine("  " + match)
        ' Keep the console window open in debug mode
        Console.WriteLine("Press any key to exit")
        Console.ReadKey()
    End Sub
    ' Function to retrieve a list of files. Note that this is a copy
    ' of the file information.
    Shared Function GetFiles(root As String) As IEnumerable(Of FileInfo)
        Return From file In My.Computer.FileSystem.GetFiles(
                   root, FileIO.SearchOption.SearchAllSubDirectories, "*.*")
               Select New FileInfo(file)
    End Function
End Class

请注意,还可以查询 RegEx 搜索返回的 MatchCollection 对象。 在本例中,只在结果中生成每个匹配项的值。 但是,也可以使用 LINQ 对集合执行筛选、排序和分组等各种操作。 由于 MatchCollection 为非泛型 IEnumerable 集合,所以必须显式声明查询中范围变量的类型。

创建 Visual Basic 控制台应用程序项目,复制并粘贴代码示例,并调整项目属性中的启动对象值。

  • LINQ 和字符串 (Visual Basic)
  • LINQ 和文件目录 (Visual Basic)
  •