如何将 LINQ 查询与正则表达式合并在一起 - Visual Basic

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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)