DataWriter class

Applies to Windows and Windows Phone

Writes data to an output stream.

Syntax


public sealed class DataWriter : IDataWriter,
    IDisposable

Attributes

[MarshalingBehavior(Agile)]
[Threading(Both)]
[Version(0x06020000)]

Members

The DataWriter class has these types of members:

Constructors

The DataWriter class has these constructors.

ConstructorDescription
DataWriter() Creates and initializes a new instance of the data writer.
DataWriter(IOutputStream) Creates and initializes a new instance of the data writer to an output stream.

 

Methods

The DataWriter class has these methods. With C#, Visual Basic, and C++, it also inherits methods from the Object class.

MethodDescription
Close [C++, JavaScript]Closes the current stream and releases system resources.
DetachBuffer Detaches the buffer that is associated with the data writer.
DetachStream Detaches the stream that is associated with the data writer.
Dispose [C#, VB]Performs tasks associated with freeing, releasing, or resetting unmanaged resources.
FlushAsync Flushes data asynchronously.
MeasureString Gets the size of a string.
StoreAsync Commits data in the buffer to a backing store.
WriteBoolean Writes a Boolean value to the output stream.
WriteBuffer(IBuffer) Writes the contents of the specified buffer to the output stream.
WriteBuffer(IBuffer, UInt32, UInt32) Writes the specified bytes from a buffer to the output stream.
WriteByte Writes a byte value to the output stream.
WriteBytes Writes an array of byte values to the output stream.
WriteDateTime Writes a date and time value to the output stream.
WriteDouble Writes a floating-point value to the output stream.
WriteGuid Writes a GUID value to the output stream.
WriteInt16 Writes a 16-bit integer value to the output stream.
WriteInt32 Writes a 32-bit integer value to the output stream.
WriteInt64 Writes a 64-bit integer value to the output stream.
WriteSingle Writes a floating-point value to the output stream.
WriteString Writes a string value to the output stream.
WriteTimeSpan Writes a time-interval value to the output stream.
WriteUInt16 Writes a 16-bit unsigned integer value to the output stream.
WriteUInt32 Writes a 32-bit unsigned integer value to the output stream.
WriteUInt64 Writes a 64-bit unsigned integer value to the output stream.

 

Properties

The DataWriter class has these properties.

PropertyAccess typeDescription

ByteOrder

Read/writeGets or sets the byte order of the data in the output stream.

UnicodeEncoding

Read/writeGets or sets the Unicode character encoding for the output stream.

UnstoredBufferLength

Read-onlyGets the size of the buffer that has not been used.

 

Examples

The following example shows how to write and read strings to an in-memory stream. For the full code sample, see Reading and writing data sample.



using System;
using System.Diagnostics;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Navigation;

// This is the click handler for the 'Copy Strings' button.  Here we will parse the
// strings contained in the ElementsToWrite text block, write them to a stream using
// DataWriter, retrieve them using DataReader, and output the results in the
// ElementsRead text block.
private async void TransferData(object sender, RoutedEventArgs e)
{
    // Initialize the in-memory stream where data will be stored.
    using (var stream = new Windows.Storage.Streams.InMemoryRandomAccessStream())
    {
        // Create the data writer object backed by the in-memory stream.
        using (var dataWriter = new Windows.Storage.Streams.DataWriter(stream))
        {
            dataWriter.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
            dataWriter.ByteOrder = Windows.Storage.Streams.ByteOrder.LittleEndian;

            // Parse the input stream and write each element separately.
            string[] inputElements = ElementsToWrite.Text.Split(';');
            foreach (string inputElement in inputElements)
            {
                uint inputElementSize = dataWriter.MeasureString(inputElement);
                dataWriter.WriteUInt32(inputElementSize);
                dataWriter.WriteString(inputElement);
            }

            // Send the contents of the writer to the backing stream.
            await dataWriter.StoreAsync();

            // For the in-memory stream implementation we are using, the flushAsync call 
            // is superfluous,but other types of streams may require it.
            await dataWriter.FlushAsync();

            // In order to prolong the lifetime of the stream, detach it from the 
            // DataWriter so that it will not be closed when Dispose() is called on 
            // dataWriter. Were we to fail to detach the stream, the call to 
            // dataWriter.Dispose() would close the underlying stream, preventing 
            // its subsequent use by the DataReader below.
            dataWriter.DetachStream();
        }

        // Create the input stream at position 0 so that the stream can be read 
        // from the beginning.
        using (var inputStream = stream.GetInputStreamAt(0))
        {
            using (var dataReader = new Windows.Storage.Streams.DataReader(inputStream))
            {
                // The encoding and byte order need to match the settings of the writer 
                // we previously used.
                dataReader.UnicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.Utf8;
                dataReader.ByteOrder = Windows.Storage.Streams.ByteOrder.LittleEndian;

                // Once we have written the contents successfully we load the stream.
                await dataReader.LoadAsync((uint)stream.Size);

                var receivedStrings = "";

                // Keep reading until we consume the complete stream.
                while (dataReader.UnconsumedBufferLength > 0)
                {
                    // Note that the call to readString requires a length of "code units" 
                    // to read. This is the reason each string is preceded by its length 
                    // when "on the wire".
                    uint bytesToRead = dataReader.ReadUInt32();
                    receivedStrings += dataReader.ReadString(bytesToRead) + "\n";
                }

                // Populate the ElementsRead text block with the items we read 
                // from the stream.
                ElementsRead.Text = receivedStrings;
            }
        }
    }
}

Requirements

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8

Namespace

Windows.Storage.Streams
Windows::Storage::Streams [C++]

Metadata

Windows.winmd

See also

Reading and writing data sample
StreamSocket sample
DataReader
DataWriterStoreOperation

 

 

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