Stream.WriteAsync Method (Byte(), Int32, Int32)
Asynchronously writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written.
Assembly: mscorlib (in mscorlib.dll)
<ComVisibleAttribute(False)> <HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading := True)> Public Function WriteAsync ( buffer As Byte(), offset As Integer, count As Integer ) As Task
The buffer to write data from.
The zero-based byte offset in buffer from which to begin copying bytes to the stream.
The maximum number of bytes to write.
Return ValueType: System.Threading.Tasks.Task
A task that represents the asynchronous write operation.
buffer is null.
offset or count is negative.
The sum of offset and count is larger than the buffer length.
The stream does not support writing.
The stream has been disposed.
The stream is currently in use by a previous write operation.
Themethod enables you to perform resource-intensive I/O operations without blocking the main thread. This performance consideration is particularly important in a Windows 8.x Store app or desktop app where a time-consuming stream operation can block the UI thread and make your app appear as if it is not working. The async methods are used in conjunction with the async and await keywords in Visual Basic and C#.
Use the CanWrite property to determine whether the current instance supports writing.
Imports System.IO Imports System.Text Class MainWindow Private Async Sub Button_Click(sender As Object, e As RoutedEventArgs) Dim uniencoding As UnicodeEncoding = New UnicodeEncoding() Dim filename As String = "c:\Users\exampleuser\Documents\userinputlog.txt" Dim result As Byte() = uniencoding.GetBytes(UserInput.Text) Using SourceStream As FileStream = File.Open(filename, FileMode.OpenOrCreate) SourceStream.Seek(0, SeekOrigin.End) Await SourceStream.WriteAsync(result, 0, result.Length) End Using End Sub End Class
Available since 4.5
Available since 4.5
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Available since 8.1