VB.Net读取和写入文本文件

StreamReader和StreamWriter类用于读取和写入数据到文本文件。这些类继承自抽象基类Stream，它支持读取和写入字节到文件流中。

StreamReader类

StreamReader类也从抽象基类TextReader继承，它代表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：

示例

以下示例演示如何读取名为 test.txt 的文本文件。该文件读取：

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

文件：fileProg.vb -

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

编译和运行程序时显示的结果如下 -

F:\worksp\vb.net\filehandle>vbc fileProg.vb
Microsoft (R) Visual Basic Compiler version 14.0.1038
for Visual Basic 2012
Copyright (c) Microsoft Corporation.  All rights reserved.
... ...
F:\worksp\vb.net\filehandle>fileProg.exe
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，它表示作者，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。 有关完整的方法列表，请访问Microsoft的文档

示例

以下示例演示如何使用StreamWriter类将文本数据写入文件中：

Imports System.IO
Module writeFile
   Sub Main()
      Dim names As String() = New String() {"Hakou Ali", "Nacy Lee", "Amir Wong", "Marry 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

执行上面示例代码，得到以下结果 -

F:\worksp\vb.net\filehandle>vbc writeFile.vb
Microsoft (R) Visual Basic Compiler version 14.0.1038
for Visual Basic 2012
Copyright (c) Microsoft Corporation.  All rights reserved.
......
F:\worksp\vb.net\filehandle>writeFile.exe
Hakou Ali
Nacy Lee
Amir Wong
Marry Amlan