WindowsRuntimeStorageExtensions::OpenStreamForReadAsync Method (IStorageFolder, String)
Retrieves a stream for reading from a file in the specified parent folder.
This API is not CLS-compliant. Namespace: System.IO
Assembly: System.Runtime.WindowsRuntime (in System.Runtime.WindowsRuntime.dll)
[CLSCompliantAttribute(false)] [ExtensionAttribute] public: static Task<Stream^>^ OpenStreamForReadAsync( IStorageFolder^ rootDirectory, String^ relativePath )
Parameters
- rootDirectory
- Type: IStorageFolder
The Windows Runtime IStorageFolder object that contains the file to read from.
- relativePath
- Type: System::String
The path, relative to the root folder, to the file to read from.
Return Value
Type: System.Threading.Tasks::Task<Stream>A task that represents the asynchronous read operation.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IStorageFolder. 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 | rootDirectory or relativePath is nullptr. |
| ArgumentException | relativePath is empty or contains only white-space characters. |
| 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 read its contents by using an instance of the StreamReader class.
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"> <Button Content="Open File" Click="Button_Click_1"></Button> <TextBlock Name="DisplayContentsBlock"></TextBlock> </StackPanel> </Page>