Visual Basic 读取和写入文本

StreamReader 和 StreamWriter 类用于从文本文件读取数据和将数据写入文本文件。这些类继承自抽象基类 Stream，抽象基类流支持将字节读写到文件流中。

StreamReader 类

StreamReader 类还继承自抽象基类 TextReader，该类表示用于读取一系列字符的读取器。

下表介绍了 StreamReader 类的一些常用方法:

实例

下面的实例演示如何读取名为 Jamaica.txt 的文本文件:

Jamaica.txt：

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

实例

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

结果如下:

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

StreamWriter 类

StreamWriter 类继承自抽象类 TextWriter，它代表写入，可以编写一系列字符。

下表显示了该类最常用的一些方法:

以上列表并不详尽。更完整的方法列表，请访问 Microsoft 的文档。

实例

以下实例演示如何使用 StreamWriter 类将文本数据写入文件中:

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

结果如下:

Hakou Ali
Nacy Lee
Amir Wong
Marry Amlan