Visual Basic 读取和写入文本

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:

编号方法名称 & 用途1Public Overrides Sub Close

关闭 StreamReader 对象和底层流，并释放与 StreamReader 关联的所有系统资源。

2Public Overrides Function Peek As Integer

返回下一个可用字符，但不使用它。

3Public Overrides Function Read As Integer

从输入流中读取下一个字符，并将字符位置前进一个字符。

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 gayAnd the sun shines daily on the mountain topI took a trip on a sailing shipAnd when I reached JamaicaI made a stop实例Imports System.IOModule 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 SubEnd Module结果如下:

Down the way where the nights are gayAnd the sun shines daily on the mountain topI took a trip on a sailing shipAnd when I reached JamaicaI 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:

编号方法名称 & 用途1Public Overrides Sub Close

关闭当前 StreamWriter 对象和流。

2Public Overrides Sub Flush

清除当前写入使用的所有缓冲区，并将所有缓冲数据写入流。

3Public Overridable Sub Write (value As Boolean)

将布尔值的文本表示形式写入文本字符串或流。 (继承自 TextWriter。)

4Public Overrides Sub Write (value As Char)

将字符写进流。

5Public Overridable Sub Write (value As Decimal)

将十进制值的文本表示形式写入文本字符串或流。

6Public Overridable Sub Write (value As Double)

将 8 字节浮点值的文本表示形式写入文本字符串或流。

7Public Overridable Sub Write (value As Integer)

将 4 字节有符号整数的文本表示形式写入文本字符串或流。

8Public Overrides Sub Write (value As String)

将字符串写入流。

9Public Overridable Sub WriteLine

将行终止符写入文本字符串或流。即写完一段文本字符后换行。

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.IOModule 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 SubEnd Module结果如下:

Hakou AliNacy LeeAmir WongMarry Amlan