Bagikan melalui

WindowsRuntimeStorageExtensions.OpenStreamForReadAsync Metode

  • Referensi

Definisi

Ruang nama:
System.IO
Rakitan:
System.Runtime.WindowsRuntime.dll

Overload

OpenStreamForReadAsync(IStorageFile)

Mengambil aliran untuk membaca dari file tertentu.
OpenStreamForReadAsync(IStorageFolder, String)

Mengambil aliran untuk membaca dari file di folder induk yang ditentukan.

OpenStreamForReadAsync(IStorageFile)

Penting

API ini bukan kompatibel CLS.

Mengambil aliran untuk membaca dari file tertentu.

public:
[System::Runtime::CompilerServices::Extension]
 static System::Threading::Tasks::Task<System::IO::Stream ^> ^ OpenStreamForReadAsync(Windows::Storage::IStorageFile ^ windowsRuntimeFile);
[System.CLSCompliant(false)]
public static System.Threading.Tasks.Task<System.IO.Stream> OpenStreamForReadAsync (this Windows.Storage.IStorageFile windowsRuntimeFile);
[<System.CLSCompliant(false)>]
static member OpenStreamForReadAsync : Windows.Storage.IStorageFile -> System.Threading.Tasks.Task<System.IO.Stream>
<Extension()>
Public Function OpenStreamForReadAsync (windowsRuntimeFile As IStorageFile) As Task(Of Stream)

Parameter

windowsRuntimeFile
IStorageFile

Objek Windows Runtime IStorageFile untuk dibaca.

Mengembalikan

Task<Stream>

Tugas yang mewakili operasi baca asinkron.

Atribut
CLSCompliantAttribute

Pengecualian

ArgumentNullException

windowsRuntimeFileadalah null.

IOException

File tidak dapat dibuka atau diambil sebagai aliran.

Contoh

Contoh berikut menunjukkan cara membuka file sebagai Stream di aplikasi Bursa Windows, dan membaca kontennya dengan menggunakan instans StreamReader kelas .

using System;
using System.IO;
using System.Text;
using Windows.Storage.Pickers;
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 Button_Click_1(object sender, RoutedEventArgs e)
        {
            StringBuilder contents = new StringBuilder();
            string nextLine;
            int lineCounter = 1;

            var openPicker = new FileOpenPicker();
            openPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
            openPicker.FileTypeFilter.Add(".txt");
            StorageFile selectedFile = await openPicker.PickSingleFileAsync();

            using (StreamReader reader = new StreamReader(await selectedFile.OpenStreamForReadAsync()))
            {
                while ((nextLine = await reader.ReadLineAsync()) != null)
                {
                    contents.AppendFormat("{0}. ", lineCounter);
                    contents.Append(nextLine);
                    contents.AppendLine();
                    lineCounter++;
                    if (lineCounter > 3)
                    {
                        contents.AppendLine("Only first 3 lines shown.");
                        break;
                    }
                }
            }
            DisplayContentsBlock.Text = contents.ToString();
        }
    }
}

Imports System.Text
Imports System.IO
Imports Windows.Storage.Pickers
Imports Windows.Storage

NotInheritable Public Class BlankPage
    Inherits Page

    

    Private Async Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
        Dim contents As StringBuilder = New StringBuilder()
        Dim nextLine As String
        Dim lineCounter As Integer = 1

        Dim openPicker = New FileOpenPicker()
        openPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary

        openPicker.FileTypeFilter.Add(".txt")
        Dim selectedFile As StorageFile = Await openPicker.PickSingleFileAsync()

        Using reader As StreamReader = New StreamReader(Await selectedFile.OpenStreamForReadAsync())
            nextLine = Await reader.ReadLineAsync()
            While (nextLine <> Nothing)
                contents.AppendFormat("{0}. ", lineCounter)
                contents.Append(nextLine)
                contents.AppendLine()
                lineCounter = lineCounter + 1
                If (lineCounter > 3) Then
                    contents.AppendLine("Only first 3 lines shown.")
                    Exit While
                End If
                nextLine = Await reader.ReadLineAsync()
            End While
        End Using
        DisplayContentsBlock.Text = contents.ToString()
    End Sub
End Class

Contoh berikutnya menunjukkan kode XAML yang terkait dengan contoh sebelumnya.

<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="Display lines from a file."></TextBlock>
        <Button Content="Load File" Click="Button_Click_1"></Button>
        <TextBlock Name="DisplayContentsBlock"></TextBlock>
    </StackPanel>
</Page>

Keterangan

Catatan

Di Visual Basic dan C#, Anda dapat memanggil metode ini sebagai metode instans pada objek jenis IStorageFileapa pun . Saat Anda menggunakan sintaks metode instans untuk memanggil metode ini, hilangkan parameter pertama. Untuk informasi selengkapnya, lihat Metode Ekstensi (Visual Basic) atau Metode Ekstensi (Panduan Pemrograman C#).

Berlaku untuk

OpenStreamForReadAsync(IStorageFolder, String)

Penting

API ini bukan kompatibel CLS.

Mengambil aliran untuk membaca dari file di folder induk yang ditentukan.

public:
[System::Runtime::CompilerServices::Extension]
 static System::Threading::Tasks::Task<System::IO::Stream ^> ^ OpenStreamForReadAsync(Windows::Storage::IStorageFolder ^ rootDirectory, System::String ^ relativePath);
[System.CLSCompliant(false)]
public static System.Threading.Tasks.Task<System.IO.Stream> OpenStreamForReadAsync (this Windows.Storage.IStorageFolder rootDirectory, string relativePath);
[<System.CLSCompliant(false)>]
static member OpenStreamForReadAsync : Windows.Storage.IStorageFolder * string -> System.Threading.Tasks.Task<System.IO.Stream>
<Extension()>
Public Function OpenStreamForReadAsync (rootDirectory As IStorageFolder, relativePath As String) As Task(Of Stream)

Parameter

rootDirectory
IStorageFolder

Objek Windows Runtime IStorageFile yang berisi file untuk dibaca.

relativePath
String

Jalur, relatif terhadap folder akar, ke file untuk dibaca.

Mengembalikan

Task<Stream>

Tugas yang mewakili operasi baca asinkron.

Atribut
CLSCompliantAttribute

Pengecualian

ArgumentNullException

rootDirectory atau relativePath adalah null.

ArgumentException

relativePath kosong atau hanya berisi karakter spasi kosong.

IOException

File tidak dapat dibuka atau diambil sebagai aliran.

Contoh

Contoh berikut menunjukkan cara membuka file sebagai Stream di aplikasi Bursa Windows, dan membaca kontennya dengan menggunakan instans StreamReader kelas .

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

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

        private async void CreateTestFile()
        {
            StorageFile newFile = await ApplicationData.Current.LocalFolder.CreateFileAsync("testfile.txt");
            await FileIO.WriteTextAsync(newFile, "example content in file");
        }

        private async void Button_Click_1(object sender, RoutedEventArgs e)
        {
            using (StreamReader reader = new StreamReader(
                await ApplicationData.Current.LocalFolder.OpenStreamForReadAsync("testfile.txt")))
            {
                string contents = await reader.ReadToEndAsync();
                DisplayContentsBlock.Text = contents;
            }
        }
    }
}

Imports System.IO
Imports Windows.Storage

NotInheritable Public Class BlankPage
    Inherits Page

    Protected Overrides Sub OnNavigatedTo(e As Navigation.NavigationEventArgs)
        CreateTestFile()
    End Sub

    Private Async Sub CreateTestFile()
        Dim newFile As StorageFile = Await ApplicationData.Current.LocalFolder.CreateFileAsync("testfile.txt")
        Await FileIO.WriteTextAsync(newFile, "example content in file")
    End Sub

    Private Async Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
        Using reader As StreamReader = New StreamReader(
                Await ApplicationData.Current.LocalFolder.OpenStreamForReadAsync("testfile.txt"))

            Dim contents As String = Await reader.ReadToEndAsync()
            DisplayContentsBlock.Text = contents
        End Using
    End Sub
End Class

Contoh berikutnya menunjukkan kode XAML yang terkait dengan contoh sebelumnya.

<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">
        <Button Content="Open File" Click="Button_Click_1"></Button>
        <TextBlock Name="DisplayContentsBlock"></TextBlock>
    </StackPanel>
</Page>

Keterangan

Catatan

Di Visual Basic dan C#, Anda dapat memanggil metode ini sebagai metode instans pada objek jenis IStorageFolder apa pun. Saat Anda menggunakan sintaks metode instans untuk memanggil metode ini, hilangkan parameter pertama. Untuk informasi selengkapnya, lihat Metode Ekstensi (Visual Basic) atau Metode Ekstensi (Panduan Pemrograman C#).

Berlaku untuk