從文字檔案讀取和寫入文字檔案

StreamReader 和 StreamWriter 類用於從文字檔案讀取資料和向文字檔案寫入資料。這些類繼承自抽象基類 Stream，該基類支援將位元組讀寫到檔案流中。

StreamReader 類

StreamReader 類也繼承自抽象基類 TextReader，該基類表示用於讀取一系列字元的讀取器。下表描述了 StreamReader 類的一些常用方法：

示例

以下示例演示瞭如何讀取名為 Jamaica.txt 的文字檔案。檔案內容如下：

Down the way where the nights are gay
And the sun shines daily on the mountain top
I took a trip on a sailing ship
And when I reached Jamaica
I made a stop

Imports System.IO
Module fileProg
   Sub Main()
      Try
         ' Create an instance of StreamReader to read from a file. 
         ' The using statement also closes the StreamReader. 
         Using sr As StreamReader = New StreamReader("e:/jamaica.txt")
            Dim line As String
            ' Read and display lines from the file until the end of  
            ' the file is reached. 
            line = sr.ReadLine()
            While (line <> Nothing)
               Console.WriteLine(line)
               line = sr.ReadLine()
            End While
         End Using
      Catch e As Exception
         ' Let the user know what went wrong.
         Console.WriteLine("The file could not be read:")
         Console.WriteLine(e.Message)
      End Try
      Console.ReadKey()
   End Sub
End Module

猜猜編譯並執行程式時會顯示什麼！

StreamWriter 類

StreamWriter 類繼承自抽象類 TextWriter，該類表示一個寫入器，可以寫入一系列字元。

下表顯示了此類的一些最常用的方法：

以上列表並不詳盡。有關方法的完整列表，請訪問 Microsoft 的文件

示例

以下示例演示瞭如何使用 StreamWriter 類將文字資料寫入檔案：

Imports System.IO
Module fileProg
   Sub Main()
      Dim names As String() = New String() {"Zara Ali", _
         "Nuha Ali", "Amir Sohel", "M Amlan"}
      Dim s As String
      Using sw As StreamWriter = New StreamWriter("names.txt")
         For Each s In names
            sw.WriteLine(s)
         Next s
      End Using
      ' Read and show each line from the file. 
      Dim line As String
      Using sr As StreamReader = New StreamReader("names.txt")
         line = sr.ReadLine()
         While (line <> Nothing)
            Console.WriteLine(line)
            line = sr.ReadLine()
         End While
      End Using
      Console.ReadKey()
   End Sub
End Module

編譯並執行上述程式碼後，將產生以下結果：

Zara Ali
Nuha Ali
Amir Sohel
M Amlan