StreamReader.Peek 方法

定義

命名空間:

System.IO

組件:

System.Runtime.dll

來源:

StreamReader.cs

傳回下一個可供使用的字元，但不使用它。

public:
 override int Peek();

public override int Peek ();

override this.Peek : unit -> int

Public Overrides Function Peek () As Integer

傳回

Int32

整數，表示要讀取的下一個字元，如果沒有要讀取的字元或資料流不支援搜尋，則為 -1。

例外狀況

IOException

發生 I/O 錯誤。

範例

下列程式代碼範例會從檔案讀取行，直到到達檔案結尾為止。

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

備註

方法會 Peek 傳回整數值，以判斷檔案的結尾還是發生另一個錯誤。 這可讓使用者先檢查傳回的值是否為 -1，再將其 Char 轉換成類型。

這個方法會覆寫 TextReader.Peek。

物件的目前位置 StreamReader 不會由 Peek變更。

另請參閱

• 檔案和資料流 I/O
• 作法：讀取檔案中的文字
• 作法：將文字寫入檔案