WindowsRuntimeStreamExtensions.AsStreamForRead Metod

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

Parametrar

Returer

Den konverterade strömmen.

Attribut

CLSCompliantAttribute

Undantag

Exempel

I följande exempel visas hur du använder metoderna AsStreamForWrite och AsStreamForRead för att konvertera en hanterad ström till och från en ström i 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

Här är XAML-koden som är associerad med föregående exempel.

<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>

Kommentarer

En standardbuffertstorlek på 16 384 byte används när strömmen konverteras. Om du vill ange en annan buffertstorlek använder du överlagringen 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

Parametrar

Returer

Den konverterade strömmen.

Attribut

CLSCompliantAttribute

Undantag

Kommentarer

Du använder den här metoden för att ange en buffertstorlek när du konverterar strömmen. Om du vill använda standardbuffertstorleken på 16 384 byte använder du överlagringen AsStreamForRead(IInputStream) .

I de flesta fall förbättrar buffring prestandan för strömåtgärder. Du kan inaktivera buffring genom att ange bufferSize noll, men du bör bara göra det när du är säker på att det är lämpligt att inaktivera buffring för din situation.