Streams.md

title	author	description	keywords	dev_langs
Streams Helper	nmetulev	There are several operations that apps need commonly to do against their APPX, or from the Internet that are not easy. This helper class wraps up some of the most common operations we need in multiple apps.	windows 10, uwp, windows community toolkit, uwp community toolkit, uwp toolkit, Streams	csharp vb

Streams Helper

There are several operations that apps need commonly to do against their APPX, or from the Internet that are not easy. Streams helper class wraps up some of the most common operations we need in multiple apps.

Some common scenarios

• Get a stream from a URI using an in memory stream (rather than needing to download it first).
• Download a URI and write it to a local storage file.
• Get a packaged file stream (files included in the APPX as Content - do not copy).
• Does a file exist local folder?
• Read text from a file using ASCII or specified encoding.

Methods

Methods	Return Type	Description
GetHttpStreamAsync(Uri, CancellationToken)	Task<IRandomAccessStream>	Get the response stream returned by a HTTP get request
GetHttpStreamToStorageFileAsync(Uri, StorageFile)	Task	Get the response stream returned by a HTTP get request and save it to a local file
GetKnowFoldersFileStreamAsync(KnownFolderId, String, FileAccessMode)	Task<IRandomAccessStream>	Return a stream to a specified file from the application local cache folder
GetLocalCacheFileStreamAsync(String, FileAccessMode)	Task<IRandomAccessStream>	Return a stream to a specified file from the application local cache folder
GetLocalFileStreamAsync(String, FileAccessMode)	Task<IRandomAccessStream>	Return a stream to a specified file from the application local folder
GetPackagedFileStreamAsync(String, FileAccessMode)	Task<IRandomAccessStream>	Return a stream to a specified file from the installation folder
IsFileExistsAsync(StorageFolder, String)	Task<bool>	Test if a file exists in the application local folder
IsKnownFolderFileExistsAsync(KnownFolderId, String)	Task<bool>	Test if a file exists in the application local cache folder
IsLocalCacheFileExistsAsync(String)	Task<bool>	Test if a file exists in the application local cache folder
IsLocalFileExistsAsync(String)	Task<bool>	Test if a file exists in the application local folder
IsPackagedFileExistsAsync(String)	Task<bool>	Test if a file exists in the application installation folder
ReadTextAsync(IRandomAccessStream, Encoding)	Task<string>	Read stream content as a string

Example

// Get access to a text file that was included in solution as Content | do not copy local
using (var stream = await StreamHelper.GetPackagedFileStreamAsync("Assets/Sub/test.txt"))
{
    // Read the contents as ASCII text
    var readText = await stream.ReadTextAsync();
}

// Get access to a HTTP resource
using (var stream = await StreamHelper.GetHttpStreamAsync(new Uri("https://dev.windows.com")))
{
    ...
}

' Get access to a text file that was included in solution as Content | do not copy local
Using stream = Await StreamHelper.GetPackagedFileStreamAsync("Assets/Sub/test.txt")
    '  Read the contents as ASCII text
    Dim readText = Await stream.ReadTextAsync()
    ...
End Using

' // Get access to a HTTP resource
Using stream = Await StreamHelper.GetHttpStreamAsync(New Uri("https://dev.windows.com"))
    ...
End Using

Sample Code

You can find more examples in our unit tests

Requirements

Device family	Universal, 10.0.16299.0 or higher
Namespace	Microsoft.Toolkit.Uwp
NuGet package	Microsoft.Toolkit.Uwp

API Source Code

• Stream Helper source code