StreamReader.Peek 方法
定义
返回下一个可用字符,但不使用它。Returns the next available character but does not consume it.
public:
override int Peek();
public override int Peek ();
override this.Peek : unit -> int
Public Overrides Function Peek () As Integer
返回
为表示下一个要读取的字符的整数,或者,如果没有要读取的字符或该流不支持查找,则为 -1。An integer representing the next character to be read, or -1 if there are no characters to be read or if the stream does not support seeking.
例外
出现 I/O 错误。An I/O error occurs.
示例
下面的代码示例读取文件中的行,直到到达文件末尾。The following code example reads lines from a file until the end of the file is reached.
using namespace System;
using namespace System::IO;
int main()
{
String^ path = "c:\\temp\\MyTest.txt";
try
{
if ( File::Exists( path ) )
{
File::Delete( path );
}
StreamWriter^ sw = gcnew StreamWriter( path );
try
{
sw->WriteLine( "This" );
sw->WriteLine( "is some text" );
sw->WriteLine( "to test" );
sw->WriteLine( "Reading" );
}
finally
{
delete sw;
}
StreamReader^ sr = gcnew StreamReader( path );
try
{
while ( sr->Peek() > -1 )
{
Console::WriteLine( sr->ReadLine() );
}
}
finally
{
delete sr;
}
}
catch ( Exception^ e )
{
Console::WriteLine( "The process failed: {0}", e );
}
}
using System;
using System.IO;
class Test
{
public static void Main()
{
string path = @"c:\temp\MyTest.txt";
try
{
if (File.Exists(path))
{
File.Delete(path);
}
using (StreamWriter sw = new StreamWriter(path))
{
sw.WriteLine("This");
sw.WriteLine("is some text");
sw.WriteLine("to test");
sw.WriteLine("Reading");
}
using (StreamReader sr = new StreamReader(path))
{
while (sr.Peek() > -1)
{
Console.WriteLine(sr.ReadLine());
}
}
}
catch (Exception e)
{
Console.WriteLine("The process failed: {0}", e.ToString());
}
}
}
Imports System.IO
Imports System.Text
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
Try
If File.Exists(path) Then
File.Delete(path)
End If
Dim sw As StreamWriter = New StreamWriter(path)
sw.WriteLine("This")
sw.WriteLine("is some text")
sw.WriteLine("to test")
sw.WriteLine("Reading")
sw.Close()
Dim sr As StreamReader = New StreamReader(path)
Do While sr.Peek() > -1
Console.WriteLine(sr.ReadLine())
Loop
sr.Close()
Catch e As Exception
Console.WriteLine("The process failed: {0}", e.ToString())
End Try
End Sub
End Class
注解
Peek方法返回一个整数值,以确定文件的末尾或发生了其他错误。The Peek method returns an integer value in order to determine whether the end of the file, or another error has occurred. 这允许用户首先检查返回值是否为-1,然后再将其强制转换为 Char 类型。This allows a user to first check if the returned value is -1 before casting it to a Char type.
此方法重写 TextReader.Peek。This method overrides TextReader.Peek.
StreamReader不会更改对象的当前位置 Peek 。The current position of the StreamReader object is not changed by Peek.