HOW TO：查詢資料夾中的檔案內容 (LINQ)
更新：2007 年 11 月
這個範例顯示如何查詢所指定目錄樹狀結構中的所有檔案、開啟每個檔案，然後檢查檔案的內容。這類技巧可以用來建立索引，或將目錄樹狀結構內容的索引反轉。在這個範例中，執行的是簡單字串搜尋。不過，您可以使用規則運算式 (Regular Expression) 執行更複雜的模式比對類型。如需詳細資訊，請參閱 HOW TO：使用規則運算式合併 LINQ 查詢。
範例
Module QueryContents
Public Sub Main()
' Modify this path as necessary.
Dim startFolder = "c:\program files\Microsoft Visual Studio 9.0\VB\"
' Take a snapshot of the file system.
Dim fileList = GetFiles(startFolder)
Dim searchTerm = "Visual Studio"
' 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 = ".htm" _
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(ByVal 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 System.IO.File.Exists(name) Then
fileContents = System.IO.File.ReadAllText(name)
End If
Return fileContents
End Function
' Function to retrieve a list of files. Note that this is a copy
' of the file information.
Function GetFiles(ByVal root As String) As System.Collections.Generic.IEnumerable(Of System.IO.FileInfo)
Return From file In My.Computer.FileSystem.GetFiles _
(root, FileIO.SearchOption.SearchAllSubDirectories, "*.*") _
Select New System.IO.FileInfo(file)
End Function
End Module
class QueryContents
{
public static void Main()
{
// Modify this path as necessary.
string startFolder = @"c:\program files\Microsoft Visual Studio 9.0\";
// Take a snapshot of the file system.
IEnumerable<System.IO.FileInfo> fileList = GetFiles(startFolder);
string searchTerm = @"Visual Studio";
// Search the contents of each file.
// A regular expression created with the RegEx class
// could be used instead of the Contains method.
// queryMatchingFiles is an IEnumerable<string>.
var queryMatchingFiles =
from file in fileList
where file.Extension == ".htm"
let fileText = GetFileText(file.FullName)
where fileText.Contains(searchTerm)
select file.FullName;
// Execute the query.
Console.WriteLine("The term \"{0}\" was found in:", searchTerm);
foreach (string filename in queryMatchingFiles)
{
Console.WriteLine(filename);
}
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
// Read the contents of the file.
static string GetFileText(string name)
{
string fileContents = String.Empty;
// If the file has been deleted since we took
// the snapshot, ignore it and return the empty string.
if (System.IO.File.Exists(name))
{
fileContents = System.IO.File.ReadAllText(name);
}
return fileContents;
}
// This method assumes that the application has discovery
// permissions for all folders under the specified path.
static IEnumerable<System.IO.FileInfo> GetFiles(string path)
{
if (!System.IO.Directory.Exists(path))
throw new System.IO.DirectoryNotFoundException();
string[] fileNames = null;
List<System.IO.FileInfo> files = new List<System.IO.FileInfo>();
fileNames = System.IO.Directory.GetFiles(path, "*.*", System.IO.SearchOption.AllDirectories);
foreach (string name in fileNames)
{
files.Add(new System.IO.FileInfo(name));
}
return files;
}
}
編譯程式碼
建立一個以 .NET Framework 3.5 版為目標的 Visual Studio 專案。此專案預設包含 System.Core.dll 的參考，以及 System.Linq 命名空間 (Namespace) 的 using 指示詞 (C#) 或 Imported 命名空間 (Visual Basic)。請在 C# 專案中，加入 System.IO 命名空間的 using 指示詞。
將此程式碼複製至您的專案。
按 F5 編譯和執行程式。
按任何鍵離開主控台視窗。
穩固程式設計
如需對多種類型的文件和檔案內容執行大量查詢作業，可考慮使用 Windows 桌面搜尋引擎。