如何将 LINQ 查询与正则表达式合并 (Visual Basic)
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。
示例
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)
Next
Next
' 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。
编译代码
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。
