HOW TO：查詢具有指定之屬性或名稱的檔案
這個範例顯示如何尋找所指定目錄樹狀結構中具有所指定副檔名 (例如 ".txt") 的所有檔案。 同時也會顯示如何根據建立時間傳回樹狀結構中最新或最舊的檔案。
範例
Module FindFileByExtension
Sub Main()
' Change the drive\path if necessary
Dim root As String = "C:\Program Files\Microsoft Visual Studio 9.0"
'Take a snapshot of the folder contents
Dim dir As New System.IO.DirectoryInfo(root)
Dim fileList = dir.GetFiles("*.*", System.IO.SearchOption.AllDirectories)
' This query will produce the full path for all .txt files
' under the specified folder including subfolders.
' It orders the list according to the file name.
Dim fileQuery = From file In fileList _
Where file.Extension = ".txt" _
Order By file.Name _
Select file
For Each file In fileQuery
Console.WriteLine(file.FullName)
Next
' Create and execute a new query by using
' the previous query as a starting point.
' fileQuery is not executed again until the
' call to Last
Dim fileQuery2 = From file In fileQuery _
Order By file.CreationTime _
Select file.Name, file.CreationTime
' Execute the query
Dim newestFile = fileQuery2.Last
Console.WriteLine("\r\nThe newest .txt file is {0}. Creation time: {1}", _
newestFile.Name, newestFile.CreationTime)
' Keep the console window open in debug mode
Console.WriteLine("Press any key to exit.")
Console.ReadKey()
End Sub
End Module
class FindFileByExtension
{
// This query will produce the full path for all .txt files
// under the specified folder including subfolders.
// It orders the list according to the file name.
static void Main()
{
string startFolder = @"c:\program files\Microsoft Visual Studio 9.0\";
// Take a snapshot of the file system.
System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(startFolder);
// This method assumes that the application has discovery permissions
// for all folders under the specified path.
IEnumerable<System.IO.FileInfo> fileList = dir.GetFiles("*.*", System.IO.SearchOption.AllDirectories);
//Create the query
IEnumerable<System.IO.FileInfo> fileQuery =
from file in fileList
where file.Extension == ".txt"
orderby file.Name
select file;
//Execute the query. This might write out a lot of files!
foreach (System.IO.FileInfo fi in fileQuery)
{
Console.WriteLine(fi.FullName);
}
// Create and execute a new query by using the previous
// query as a starting point. fileQuery is not
// executed again until the call to Last()
var newestFile =
(from file in fileQuery
orderby file.CreationTime
select new { file.FullName, file.CreationTime })
.Last();
Console.WriteLine("\r\nThe newest .txt file is {0}. Creation time: {1}",
newestFile.FullName, newestFile.CreationTime);
// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit");
Console.ReadKey();
}
}
編譯程式碼
建立一個以 .NET Framework 3.5 版為目標的 Visual Studio 專案。 根據預設，專案有 System.Core.dll 的參考，以及 System.Linq 命名空間的 using 指示詞 (C#) 或 Imports 陳述式 (Visual Basic)。 請在 C# 專案中，加入 System.IO 命名空間的 using 指示詞。
請將這段程式碼複製到您的專案，
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。