WindowsRuntimeStorageExtensions.OpenStreamForReadAsync 方法

參考

定義

命名空間:: System.IO

組件:: System.Runtime.WindowsRuntime.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

多載

OpenStreamForReadAsync(IStorageFile)	從指定檔案擷取資料流進行讀取。
OpenStreamForReadAsync(IStorageFolder, String)	從指定上層資料夾中的檔案中擷取資料流進行讀取。

OpenStreamForReadAsync(IStorageFile)

重要

此 API 不符合 CLS 規範。

從指定檔案擷取資料流進行讀取。

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)

參數

windowsRuntimeFile: IStorageFile

要從中讀取的 Windows 執行階段 IStorageFile 物件。

傳回

Task<Stream>

表示非同步讀取作業的工作。

屬性: CLSCompliantAttribute

例外狀況

ArgumentNullException

windowsRuntimeFile 為 null。

IOException

檔案無法開啟，或無法擷取成資料流。

範例

下列範例示範如何在 Windows 市集應用程式中開啟檔案做為 Stream ，並使用類別的 StreamReader 實例來讀取其內容。

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

下一個範例顯示與上一個範例相關聯的 XAML 程式代碼。

<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>

備註

注意

在 Visual Basic 和 C# 中，您可以將這個方法呼叫為類型 IStorageFile之任何對象的實例方法。使用執行個體方法語法呼叫這個方法時，請省略第一個參數。如需詳細資訊，請參閱 Visual Basic) 或擴充方法 ( (C# 程式設計指南中的擴充方法) 。

適用於

OpenStreamForReadAsync(IStorageFolder, String)

重要

此 API 不符合 CLS 規範。

從指定上層資料夾中的檔案中擷取資料流進行讀取。

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)

參數

rootDirectory: IStorageFolder

包含做為讀取來源檔案的 Windows 執行階段 IStorageFile 物件。

relativePath: String

要讀取之檔案的路徑（相對於根資料夾）。

傳回

Task<Stream>

表示非同步讀取作業的工作。

屬性: CLSCompliantAttribute

例外狀況

ArgumentNullException

rootDirectory 或 relativePath 為 null。

ArgumentException

relativePath 是空的或僅包含空白字元。

IOException

檔案無法開啟，或無法擷取成資料流。

範例

下列範例示範如何在 Windows 市集應用程式中開啟檔案做為 Stream ，並使用類別的 StreamReader 實例來讀取其內容。

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

下一個範例顯示與上一個範例相關聯的 XAML 程式代碼。

<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>

備註

注意

在 Visual Basic 和 C# 中，您可以在 IStorageFolder 類型的任何物件上呼叫此方法作為實例方法。使用執行個體方法語法呼叫這個方法時，請省略第一個參數。如需詳細資訊，請參閱 Visual Basic) 或擴充方法 ( (C# 程式設計指南中的擴充方法) 。

適用於

共用方式為

WindowsRuntimeStorageExtensions.OpenStreamForReadAsync 方法

定義

多載

OpenStreamForReadAsync(IStorageFile)

參數

傳回

例外狀況

範例

備註

適用於

OpenStreamForReadAsync(IStorageFolder, String)

參數

傳回

例外狀況

範例

備註

適用於

其他資源