如何合併 LINQ 查詢與規則運算式 (Visual Basic)
此範例會示範如何使用 Regex 類別來建立規則運算式，以在文字字串中進行更複雜的比對。 LINQ 查詢讓您輕鬆地準確篩選出您想要用規則運算式搜尋的檔案，並調整結果。
範例
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
請注意，您也可以對由 Regex 搜尋所傳回的 MatchCollection 物件進行查詢。 在本例中，結果只會產生每個相符項目的值。 不過，它也可以使用 LINQ 對該集合執行所有種類的篩選、排序及群組。 因為 MatchCollection 為非泛型 IEnumerable 集合，所以您必須在查詢中明確地陳述範圍變數的類型。
編譯程式碼
建立 Visual Basic 主控台應用程式專案、複製並貼上程式碼範例，以及調整專案屬性中的 Startup 物件值。
