此示例演示如何查询指定目录树中的所有文件、打开每个文件并检查其内容。 此类技术可用于对目录树的内容创建索引或反向索引。 此示例中执行的是简单的字符串搜索。 但是，可使用正则表达式执行类型更复杂的模式匹配。 有关详细信息，请参阅如何：将 LINQ 查询与正则表达式合并在一起 (Visual Basic)。
示例
Imports System.IO
Module Module1
'QueryContents
Public Sub Main()
' Modify this path as necessary.
Dim startFolder = "C:\Program Files (x86)\Microsoft Visual Studio 14.0"
' Take a snapshot of the folder contents.
Dim dir As New DirectoryInfo(startFolder)
Dim fileList = dir.GetFiles("*.*", SearchOption.AllDirectories)
Dim searchTerm = "Welcome"
' Search the contents of each file.
' A regular expression created with the Regex class
' could be used instead of the Contains method.
Dim queryMatchingFiles = From file In fileList _
Where file.Extension = ".html" _
Let fileText = GetFileText(file.FullName) _
Where fileText.Contains(searchTerm) _
Select file.FullName
Console.WriteLine("The term " & searchTerm & " was found in:")
' Execute the query.
For Each filename In queryMatchingFiles
Console.WriteLine(filename)
Next
' Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit")
Console.ReadKey()
End Sub
' Read the contents of the file. This is done in a separate
' function in order to handle potential file system errors.
Function GetFileText(name As String) As String
' If the file has been deleted, the right thing
' to do in this case is return an empty string.
Dim fileContents = String.Empty
' If the file has been deleted since we took
' the snapshot, ignore it and return the empty string.
If File.Exists(name) Then
fileContents = File.ReadAllText(name)
End If
Return fileContents
End Function
End Module
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。
