WindowsRuntimeStorageExtensions.OpenStreamForWriteAsync Method (IStorageFile)
.NET Framework 4.5
Retrieves a stream for writing to a specified file.
Assembly: System.Runtime.WindowsRuntime (in System.Runtime.WindowsRuntime.dll)
[CLSCompliantAttribute(false)] public static Task<Stream> OpenStreamForWriteAsync( this IStorageFile windowsRuntimeFile )
Parameters
- windowsRuntimeFile
- Type: IStorageFile
The Windows Runtime IStorageFile object to write to.
Return Value
Type: System.Threading.Tasks.Task<Stream>A task that represents the asynchronous write operation.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IStorageFile. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).| Exception | Condition |
|---|---|
| ArgumentNullException | windowsRuntimeFile is null. |
| IOException | The file could not be opened or retrieved as a stream. |
The following example shows how to open a file in the application data as a Stream in a Windows Store app, and write to it by using an instance of the StreamWriter class.
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("testfile3.txt"); using (StreamWriter writer = new StreamWriter(await newFile.OpenStreamForWriteAsync())) { await writer.WriteLineAsync("new entry"); await writer.WriteLineAsync(UserText.Text); } } private async void VerifyButton_Click(object sender, RoutedEventArgs e) { StorageFile openedFile = await ApplicationData.Current.LocalFolder.GetFileAsync("testfile3.txt"); using (StreamReader reader = new StreamReader(await openedFile.OpenStreamForReadAsync())) { Results.Text = await reader.ReadToEndAsync(); } } } }
The next example shows the XAML code that is associated with the previous example.
<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>
Windows 8, Windows Server 2012
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
