WindowsRuntimeStreamExtensions.AsStreamForRead Metodo

public:
[System::Runtime::CompilerServices::Extension]
 static System::IO::Stream ^ AsStreamForRead(Windows::Storage::Streams::IInputStream ^ windowsRuntimeStream);

[System.CLSCompliant(false)]
public static System.IO.Stream AsStreamForRead (this Windows.Storage.Streams.IInputStream windowsRuntimeStream);

[<System.CLSCompliant(false)>]
static member AsStreamForRead : Windows.Storage.Streams.IInputStream -> System.IO.Stream

<Extension()>
Public Function AsStreamForRead (windowsRuntimeStream As IInputStream) As Stream

Parametri

Restituisce

Flusso convertito.

Attributi

CLSCompliantAttribute

Eccezioni

Esempio

Nell'esempio seguente viene illustrato come usare i AsStreamForWrite metodi e AsStreamForRead per convertire un flusso gestito in e da un flusso nel Windows Runtime.

using System;
using System.IO;
using Windows.Storage;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace ExampleApplication
{
    public sealed partial class BlankPage : Page
    {
        public BlankPage()
        {
            this.InitializeComponent();
        }

        private async void CreateButton_Click(object sender, RoutedEventArgs e)
        {
            StorageFile newFile = await ApplicationData.Current.LocalFolder.CreateFileAsync("testfile.txt");
            var streamNewFile = await newFile.OpenAsync(FileAccessMode.ReadWrite);

            using (var outputNewFile = streamNewFile.GetOutputStreamAt(0))
            {
                using (StreamWriter writer = new StreamWriter(outputNewFile.AsStreamForWrite()))
                {
                    await writer.WriteLineAsync("content for new file");
                    await writer.WriteLineAsync(UserText.Text);
                }
            }
        }

        private async void VerifyButton_Click(object sender, RoutedEventArgs e)
        {
            StorageFile openedFile = await ApplicationData.Current.LocalFolder.GetFileAsync("testfile.txt");
            var streamOpenedFile = await openedFile.OpenAsync(FileAccessMode.Read);

            using (var inputOpenedFile = streamOpenedFile.GetInputStreamAt(0))
            {
                using (StreamReader reader = new StreamReader(inputOpenedFile.AsStreamForRead()))
                {
                    Results.Text = await reader.ReadToEndAsync();
                }
            }
        }
    }
}

Imports System.IO
Imports Windows.Storage

NotInheritable Public Class BlankPage
    Inherits Page

    Private Async Sub CreateButton_Click(sender As Object, e As RoutedEventArgs)
        Dim newFile As StorageFile = Await ApplicationData.Current.LocalFolder.CreateFileAsync("testfile.txt")
        Dim streamNewFile = Await newFile.OpenAsync(FileAccessMode.ReadWrite)

        Using outputNewFile = streamNewFile.GetOutputStreamAt(0)
            Using writer As StreamWriter = New StreamWriter(outputNewFile.AsStreamForWrite())
                Await writer.WriteLineAsync("content for new file")
                Await writer.WriteLineAsync(UserText.Text)
            End Using
        End Using
    End Sub

    Private Async Sub VerifyButton_Click(sender As Object, e As RoutedEventArgs)
        Dim openedFile As StorageFile = Await ApplicationData.Current.LocalFolder.GetFileAsync("testfile.txt")
        Dim streamOpenedFile = Await openedFile.OpenAsync(FileAccessMode.Read)

        Using inputOpenedFile = streamOpenedFile.GetInputStreamAt(0)

            Using reader As StreamReader = New StreamReader(inputOpenedFile.AsStreamForRead())
                Results.Text = Await reader.ReadToEndAsync()
            End Using
        End Using
    End Sub
End Class

Ecco il codice XAML associato all'esempio precedente.

<Page
    x:Class="ExampleApplication.BlankPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:ExampleApplication"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <StackPanel Background="{StaticResource ApplicationPageBackgroundBrush}" VerticalAlignment="Center" HorizontalAlignment="Center">
        <TextBlock Text="Provide text to write to file:"></TextBlock>
        <TextBox Name="UserText" Width="400"></TextBox>
        <Button Name="CreateButton" Content="Create File" Click="CreateButton_Click"></Button>
        <Button Name="VerifyButton" Content="Verify Contents" Click="VerifyButton_Click"></Button>
        <TextBlock Name="Results"></TextBlock>
    </StackPanel>
</Page>

Commenti

Durante la conversione del flusso viene usata una dimensione del buffer predefinita di 16.384 byte. Per specificare una dimensione del buffer diversa, usare l'overload AsStreamForRead(IInputStream, Int32) .

public:
[System::Runtime::CompilerServices::Extension]
 static System::IO::Stream ^ AsStreamForRead(Windows::Storage::Streams::IInputStream ^ windowsRuntimeStream, int bufferSize);

[System.CLSCompliant(false)]
public static System.IO.Stream AsStreamForRead (this Windows.Storage.Streams.IInputStream windowsRuntimeStream, int bufferSize);

[<System.CLSCompliant(false)>]
static member AsStreamForRead : Windows.Storage.Streams.IInputStream * int -> System.IO.Stream

<Extension()>
Public Function AsStreamForRead (windowsRuntimeStream As IInputStream, bufferSize As Integer) As Stream

Parametri

Restituisce

Flusso convertito.

Attributi

CLSCompliantAttribute

Eccezioni

Commenti

Questo metodo consente di specificare una dimensione del buffer durante la conversione del flusso. Per usare le dimensioni predefinite del buffer di 16.384 byte, usare l'overload AsStreamForRead(IInputStream) .

Nella maggior parte delle situazioni, il buffering migliora le prestazioni delle operazioni di flusso. È possibile disabilitare il buffer impostando bufferSize su zero, ma è consigliabile eseguire questa operazione solo quando si è certi che la disabilitazione del buffer sia appropriata per la situazione.