However, the IsAsync property does not have to be true to call the ReadAsync, WriteAsync, or CopyToAsync method. When the property is true, the stream utilizes overlapped I/O to perform file operations asynchronously. You specify this value when you create an instance of the FileStream class using a constructor that has an isAsync, useAsync, or options parameter. The IsAsync property detects whether the file handle was opened asynchronously. For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic. To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). To dispose of the type directly, call its Dispose method in a try/ catch block. When you have finished using the type, you should dispose of it either directly or indirectly. This type implements the IDisposable interface.
FileStream buffers input and output for better performance.
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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. Use the asynchronous methods to perform resource-intensive file operations without blocking the main thread. You can use the Read, Write, CopyTo, and Flush methods to perform synchronous operations, or the ReadAsync, WriteAsync, CopyToAsync, and FlushAsync methods to perform asynchronous operations. Use the FileStream class to read from, write to, open, and close files on a file system, and to manipulate other file-related operating system handles, including pipes, standard input, and standard output. Using SourceStream As FileStream = File.Open(filename, FileMode.OpenOrCreate)Īwait SourceStream.WriteAsync(result, 0, result.Length) Private Async Sub Button_Click(sender As Object, e As RoutedEventArgs)ĭim uniencoding As UnicodeEncoding = New UnicodeEncoding()ĭim filename As String = "c:\Users\exampleuser\Documents\userinputlog.txt"ĭim result As Byte() = uniencoding.GetBytes(UserInput.Text) Using (FileStream SourceStream = File.Open(filename, FileMode.OpenOrCreate))Īwait SourceStream.WriteAsync(result, 0, result.Length) String filename = result = uniencoding.GetBytes(UserInput.Text) UnicodeEncoding uniencoding = new UnicodeEncoding() Private async void Button_Click(object sender, RoutedEventArgs e) The file path needs to be changed to a file that exists on the computer.
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This code runs in a WPF app that has a TextBlock named UserInput and a button hooked up to a Click event handler that is named Button_Click.
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The following example shows how to write to a file asynchronously.
Private Shared Sub AddText(ByVal fs As FileStream, ByVal value As String)ĭim info As Byte() = New UTF8Encoding(True).GetBytes(value)
Private static void AddText(FileStream fs, string value)īyte info = new UTF8Encoding(true).GetBytes(value) ĭim path As String = "c:\temp\MyTest.txt"ĪddText(fs, Environment.NewLine & "and this is on a new line")ĪddText(fs, Environment.NewLine & Environment.NewLine)ĪddText(fs, "The following is a subset of characters:" & Environment.NewLine)ĪddText(fs, Convert.ToChar(i).ToString())ĭim temp As UTF8Encoding = New UTF8Encoding(True) Using (FileStream fs = File.Create(path))ĪddText(fs, "\r\nand this is on a new line") ĪddText(fs, "\r\n\r\nThe following is a subset of characters:\r\n") String path = Delete the file if it exists. While ( fs->Read( b, 0, b->Length ) > 0 )Ĭonsole::WriteLine( temp->GetString( b ) ) UTF8Encoding^ temp = gcnew UTF8Encoding( true ) Void AddText( FileStream^ fs, String^ value )Īrray^info = (gcnew UTF8Encoding( true ))->GetBytes( value ) ĪddText( fs, "This is some more text," ) ĪddText( fs, "\r\nand this is on a new line" ) ĪddText( fs, "\r\n\r\nThe following is a subset of characters:\r\n" ) įor ( int i = 1 i ^b = gcnew array(1024) The following example demonstrates some of the FileStream constructors.
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