WindowsRuntimeStorageExtensions.OpenStreamForWriteAsync Method (IStorageFile)

.NET Framework (current version)

Retrieves a stream for writing to a specified file.

This API is not CLS-compliant. 

Namespace:  System.IO
Assembly:  System.Runtime.WindowsRuntime (in System.Runtime.WindowsRuntime.dll)

<ExtensionAttribute> _
<CLSCompliantAttribute(False)> _
Public Shared Function OpenStreamForWriteAsync ( _
	windowsRuntimeFile As IStorageFile _
) As Task(Of Stream)


Type: IStorageFile

The Windows Runtime IStorageFile object to write to.

Return Value

Type: System.Threading.Tasks.Task(Of 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).


windowsRuntimeFile is Nothing.


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.

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("testfile4.txt")

        Using writer As StreamWriter = New StreamWriter(Await newFile.OpenStreamForWriteAsync())
            Await writer.WriteLineAsync("new entry")
            Await writer.WriteLineAsync(UserText.Text)
        End Using 
    End Sub 

    Private Async Sub VerifyButton_Click(sender As Object, e As RoutedEventArgs)
        Dim openedFile As StorageFile = Await ApplicationData.Current.LocalFolder.GetFileAsync("testfile4.txt")
        Using reader As StreamReader = New StreamReader(Await openedFile.OpenStreamForReadAsync())
            Results.Text = Await reader.ReadToEndAsync()
        End Using 
    End Sub 
End Class

The next example shows the XAML code that is associated with the previous example.


    <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>

.NET Framework

Supported in: 4.6, 4.5

.NET for Windows Phone apps

Supported in: Windows Phone Silverlight 8