DataWriter DataWriter DataWriter DataWriter Class

Writes data to an output stream.

Syntax

Declaration

public sealed class DataWriterpublic sealed class DataWriterPublic NotInheritable Class DataWriter

Remarks

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.

#include "pch.h"
#include "WriteReadStream.xaml.h"

using namespace Concurrency;
using namespace DataReaderWriter;
using namespace Platform;
using namespace Windows::Storage::Streams;
using namespace Windows::UI::Xaml;
using namespace Windows::UI::Xaml::Controls;
using namespace Windows::UI::Xaml::Navigation;

Array<String^>^ _inputElements = ref new Array<String^>
{
    "Hello", "World", "1 2 3 4 5", "Très bien!", "Goodbye"
};

WriteReadStream::WriteReadStream()
{
    InitializeComponent();

    // Populate the text block with the input elements.
    ElementsToWrite->Text = "";
    for (unsigned int i = 0; i < _inputElements->Length; i++)
    {
        ElementsToWrite->Text += _inputElements[i] + ";";
    }
}

// Invoked when this page is about to be displayed in a Frame.
void WriteReadStream::OnNavigatedTo(NavigationEventArgs^ e)
{
    // Get a pointer to our main page.
    rootPage = MainPage::Current;
}

// 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.
void DataReaderWriter::WriteReadStream::TransferData(
Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
    // Initialize the in-memory stream where data will be stored.
    InMemoryRandomAccessStream^ stream = ref new InMemoryRandomAccessStream();

    // Create the DataWriter object backed by the in-memory stream.  When
    // dataWriter is deleted, it will also close the underlying stream.
    DataWriter^ dataWriter = ref new DataWriter(stream);
    dataWriter->UnicodeEncoding = UnicodeEncoding::Utf8;
    dataWriter->ByteOrder = ByteOrder::LittleEndian;

    // Create the data reader by using the input stream set at position 0 so that 
    // the stream will be read from the beginning regardless of where the position
    // the original stream ends up in after the store.
    IInputStream^ inputStream = stream->GetInputStreamAt(0);
    DataReader^ dataReader = ref new DataReader(inputStream);
    // The encoding and byte order need to match the settings of the writer 
    / we previously used.
    dataReader->UnicodeEncoding = UnicodeEncoding::Utf8;
    dataReader->ByteOrder = ByteOrder::LittleEndian;

    // Write the input data to the output stream.  Serialize the elements by writing
    // each string separately, preceded by its length.
    for (unsigned int i = 0; i < _inputElements->Length; i++) 
    {
        unsigned int inputElementSize = dataWriter->MeasureString(_inputElements[i]);
        dataWriter->WriteUInt32(inputElementSize);
        dataWriter->WriteString(_inputElements[i]);
    }

    // Send the contents of the writer to the backing stream.
    create_task(dataWriter->StoreAsync()).then([this, dataWriter] (unsigned int bytesStored)
    {
        // For the in-memory stream implementation we are using, the FlushAsync() call 
        // is superfluous, but other types of streams may require it.
        return dataWriter->FlushAsync();
    }).then([this, dataReader, stream] (bool flushOp)
    {
        // Once we have written the contents successfully we load the stream.
        return dataReader->LoadAsync((unsigned int) stream->Size);
    }).then([this, dataReader] (task<unsigned int> bytesLoaded)
    {
        try
        {
            // Check for possible exceptions that could have been thrown 
            // in the async call chain.
            bytesLoaded.get();

            String^ readFromStream = "";

            // 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".
                unsigned int bytesToRead = dataReader->ReadUInt32();
                readFromStream += dataReader->ReadString(bytesToRead) + "\n";
            }

            // Populate the ElementsRead text block with the items we read from the stream
            ElementsRead->Text = readFromStream;
        }
        catch (Exception^ e)
        {
            ElementsRead->Text = "Error: " + e->Message;
        }
    });
}

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;
            }
        }
    }
}

(function () {
    "use strict";
    var page = WinJS.UI.Pages.define("/html/write-read-stream.html", {
        ready: function (element, options) {
            var sourceElement = document.getElementById("ElementsToSend");
            sourceElement.innerHTML = "Hello;World;1 2 3 4 5;Très bien!;Goodbye";
            var sendButton = document.getElementById("SendButton");
            sendButton.addEventListener("click", transferData);
        }
    });

function transferData() {
        var sourceElement = document.getElementById("ElementsToSend");
        var destinationElement = document.getElementById("scenario1Output");

        // First a DataWriter object is created, backed by an in-memory stream where 
        // the data will be stored.
        var writer = Windows.Storage.Streams.DataWriter(
            new Windows.Storage.Streams.InMemoryRandomAccessStream());
        writer.unicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.utf8;
        writer.byteOrder = Windows.Storage.Streams.ByteOrder.littleEndian;

        // We separate the contents of the sourceElement div in multiple strings 
        // using ';' as the separator. Each string will be written separately.
        var elements = sourceElement.innerHTML.split(";");
        elements.forEach(function (element) {
            var codeUnits = writer.measureString(element);
            writer.writeInt32(codeUnits);
            writer.writeString(element);
        });

        var reader;
        var stream;

        // The call to store async sends the actual contents of the writer 
        // to the backing stream.
        writer.storeAsync().then(function () {
            // For the in-memory stream implementation we are using, the flushAsync call 
            // is superfluous, but other types of streams may require it.
            return writer.flushAsync();
        }).then(function () {
            // We detach the stream to prolong its useful lifetime. Were we to fail 
            // to detach the stream, the call to writer.close() would close the underlying 
            // stream, preventing its subsequent use by the DataReader below. Most clients 
            // of DataWriter will have no reason to use the underlying stream after 
            // writer.close() is called, and will therefore have no reason to call
            // writer.detachStream(). Note that once we detach the stream, we assume 
            // responsibility for closing the stream subsequently; after the stream 
            // has been detached, a call to writer.close() will have no effect on the stream.
            stream = writer.detachStream();
            // Make sure the stream is read from the beginning in the reader 
            // we are creating below.
            stream.seek(0);
            // Most DataWriter clients will not call writer.detachStream(), 
            // and furthermore will be working with a file-backed or network-backed stream, 
            // rather than an in-memory-stream. In such cases, it would be particularly 
            // important to call writer.close(). Doing so is always a best practice.
            writer.close();

            reader = new Windows.Storage.Streams.DataReader(stream);
            // The encoding and byte order need to match the settings of the writer 
            // we previously used.
            reader.unicodeEncoding = Windows.Storage.Streams.UnicodeEncoding.utf8;
            reader.byteOrder = Windows.Storage.Streams.ByteOrder.littleEndian;
            // Once we have written the contents successfully we load the stream, 
            // this is also an asynchronous operation
            return reader.loadAsync(stream.size);
        }).done(function () {
            var receivedStrings = "";
            // Keep reading until we consume the complete stream
            while (reader.unconsumedBufferLength > 0) {
                // Note that the call to readString requires a length of "code units" 
                // to read. This is the reason each string is preceeded by its length 
                // when "on the wire".
                var codeUnitsToRead = reader.readInt32();
                receivedStrings += reader.readString(codeUnitsToRead) + "<br/>";
            }
            // Calling reader.close() closes the underlying stream. It would be particularly important
            // to call reader.close() if the underlying stream were file-backed or 
            // network-backed. Note that this call to reader.close() satisfies 
            // our obligation to close the stream previously detached from DataReader.
            reader.close();
            destinationElement.innerHTML = receivedStrings;
        });
    };
})();

Constructors summary

Creates and initializes a new instance of the data writer.

Creates and initializes a new instance of the data writer to an output stream.

Properties summary

Gets or sets the byte order of the data in the output stream.

Gets or sets the Unicode character encoding for the output stream.

Gets the size of the buffer that has not been used.

Methods summary

Closes the current stream and releases system resources.

Detaches the buffer that is associated with the data writer.

Detaches the stream that is associated with the data writer.

Flushes data asynchronously.

Gets the size of a string.

Commits data in the buffer to a backing store.

Writes a Boolean value to the output stream.

Writes the contents of the specified buffer to the output stream.

Writes the specified bytes from a buffer to the output stream.

Writes a byte value to the output stream.

Writes an array of byte values to the output stream.

Writes a date and time value to the output stream.

Writes a floating-point value to the output stream.

Writes a GUID value to the output stream.

Writes a 16-bit integer value to the output stream.

Writes a 32-bit integer value to the output stream.

Writes a 64-bit integer value to the output stream.

Writes a floating-point value to the output stream.

Writes a string value to the output stream.

Writes a time-interval value to the output stream.

Writes a 16-bit unsigned integer value to the output stream.

Writes a 32-bit unsigned integer value to the output stream.

Writes a 64-bit unsigned integer value to the output stream.

Constructors

  • DataWriter()
    DataWriter()
    DataWriter()
    DataWriter()

    Creates and initializes a new instance of the data writer.

    public DataWriter()public DataWriter()Public Function DataWriter() As
  • DataWriter(Windows.Storage.Streams.IOutputStream)
    DataWriter(Windows.Storage.Streams.IOutputStream)
    DataWriter(Windows.Storage.Streams.IOutputStream)
    DataWriter(Windows.Storage.Streams.IOutputStream)

    Creates and initializes a new instance of the data writer to an output stream.

    public DataWriter(Windows.Storage.Streams.IOutputStream)public DataWriter(Windows.Storage.Streams.IOutputStream)Public Function DataWriter(Windows.Storage.Streams.IOutputStream) As

    Parameters

Properties

  • ByteOrder
    ByteOrder
    ByteOrder
    ByteOrder

    Gets or sets the byte order of the data in the output stream.

    public ByteOrder ByteOrder { get; set; }public ByteOrder ByteOrder { get; set; }Public ReadWrite Property ByteOrder As ByteOrder

    Property Value

  • UnicodeEncoding
    UnicodeEncoding
    UnicodeEncoding
    UnicodeEncoding

    Gets or sets the Unicode character encoding for the output stream.

    public UnicodeEncoding UnicodeEncoding { get; set; }public UnicodeEncoding UnicodeEncoding { get; set; }Public ReadWrite Property UnicodeEncoding As UnicodeEncoding

    Property Value

  • UnstoredBufferLength
    UnstoredBufferLength
    UnstoredBufferLength
    UnstoredBufferLength

    Gets the size of the buffer that has not been used.

    public uint UnstoredBufferLength { get; }public uint UnstoredBufferLength { get; }Public ReadOnly Property UnstoredBufferLength As uint

    Property Value

    • uint
      uint
      uint
      uint

      The size of the buffer that has not been used, in bytes.

Methods

  • Close()
    Close()
    Close()
    Close()

    Closes the current stream and releases system resources.

    public void Close()public void Close()Public Function Close() As void

    Remarks

    DataWriter takes ownership of the stream that is passed to its constructor. Calling this method also calls on the associated stream. After calling this method, calls to most other DataWriter methods will fail.

    If you do not want the associated stream to be closed when the reader closes, call DetachStream() before calling this method.

  • DetachBuffer()
    DetachBuffer()
    DetachBuffer()
    DetachBuffer()

    Detaches the buffer that is associated with the data writer.

    public IBuffer DetachBuffer()public IBuffer DetachBuffer()Public Function DetachBuffer() As IBuffer

    Returns

  • DetachStream()
    DetachStream()
    DetachStream()
    DetachStream()

    Detaches the stream that is associated with the data writer.

    public IOutputStream DetachStream()public IOutputStream DetachStream()Public Function DetachStream() As IOutputStream

    Returns

  • FlushAsync()
    FlushAsync()
    FlushAsync()
    FlushAsync()

    Flushes data asynchronously.

    public IAsyncOperation<bool> FlushAsync()public IAsyncOperation<bool> FlushAsync()Public Function FlushAsync() As IAsyncOperation( Of bool )

    Returns

    • The stream flush operation.

  • MeasureString(System.String)
    MeasureString(System.String)
    MeasureString(System.String)
    MeasureString(System.String)

    Gets the size of a string.

    public uint MeasureString(System.String)public uint MeasureString(System.String)Public Function MeasureString(System.String) As uint

    Parameters

    • value
      System.String
      System.String
      System.String
      System.String

      The string.

    Returns

    • uint
      uint
      uint
      uint

      The size of the string, in bytes.

  • StoreAsync()
    StoreAsync()
    StoreAsync()
    StoreAsync()

    Commits data in the buffer to a backing store.

    public DataWriterStoreOperation StoreAsync()public DataWriterStoreOperation StoreAsync()Public Function StoreAsync() As DataWriterStoreOperation

    Returns

  • WriteBoolean(System.Boolean)
    WriteBoolean(System.Boolean)
    WriteBoolean(System.Boolean)
    WriteBoolean(System.Boolean)

    Writes a Boolean value to the output stream.

    public void WriteBoolean(System.Boolean)public void WriteBoolean(System.Boolean)Public Function WriteBoolean(System.Boolean) As void

    Parameters

    • value
      System.Boolean
      System.Boolean
      System.Boolean
      System.Boolean

      The value.

  • WriteBuffer(Windows.Storage.Streams.IBuffer)
    WriteBuffer(Windows.Storage.Streams.IBuffer)
    WriteBuffer(Windows.Storage.Streams.IBuffer)
    WriteBuffer(Windows.Storage.Streams.IBuffer)

    Writes the contents of the specified buffer to the output stream.

    public void WriteBuffer(Windows.Storage.Streams.IBuffer)public void WriteBuffer(Windows.Storage.Streams.IBuffer)Public Function WriteBuffer(Windows.Storage.Streams.IBuffer) As void

    Parameters

  • WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)
    WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)
    WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)
    WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)

    Writes the specified bytes from a buffer to the output stream.

    public void WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)public void WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32)Public Function WriteBuffer(Windows.Storage.Streams.IBuffer,System.UInt32,System.UInt32) As void

    Parameters

    • buffer

      The buffer.

    • start
      System.UInt32
      System.UInt32
      System.UInt32
      System.UInt32

      The starting byte.

    • count
      System.UInt32
      System.UInt32
      System.UInt32
      System.UInt32

      The number of bytes to write.

  • WriteByte(System.Byte)
    WriteByte(System.Byte)
    WriteByte(System.Byte)
    WriteByte(System.Byte)

    Writes a byte value to the output stream.

    public void WriteByte(System.Byte)public void WriteByte(System.Byte)Public Function WriteByte(System.Byte) As void

    Parameters

    • value
      System.Byte
      System.Byte
      System.Byte
      System.Byte

      The value.

  • WriteBytes(System.Byte[])
    WriteBytes(System.Byte[])
    WriteBytes(System.Byte[])
    WriteBytes(System.Byte[])

    Writes an array of byte values to the output stream.

    public void WriteBytes(System.Byte[])public void WriteBytes(System.Byte[])Public Function WriteBytes(System.Byte[]) As void

    Parameters

    • value
      System.Byte[]
      System.Byte[]
      System.Byte[]
      System.Byte[]

      The array of values.

  • WriteDateTime(Windows.Foundation.DateTime)
    WriteDateTime(Windows.Foundation.DateTime)
    WriteDateTime(Windows.Foundation.DateTime)
    WriteDateTime(Windows.Foundation.DateTime)

    Writes a date and time value to the output stream.

    public void WriteDateTime(Windows.Foundation.DateTime)public void WriteDateTime(Windows.Foundation.DateTime)Public Function WriteDateTime(Windows.Foundation.DateTime) As void

    Parameters

  • WriteDouble(System.Double)
    WriteDouble(System.Double)
    WriteDouble(System.Double)
    WriteDouble(System.Double)

    Writes a floating-point value to the output stream.

    public void WriteDouble(System.Double)public void WriteDouble(System.Double)Public Function WriteDouble(System.Double) As void

    Parameters

    • value
      System.Double
      System.Double
      System.Double
      System.Double

      The value.

  • WriteGuid(System.Guid)
    WriteGuid(System.Guid)
    WriteGuid(System.Guid)
    WriteGuid(System.Guid)

    Writes a GUID value to the output stream.

    public void WriteGuid(System.Guid)public void WriteGuid(System.Guid)Public Function WriteGuid(System.Guid) As void

    Parameters

    • value
      System.Guid
      System.Guid
      System.Guid
      System.Guid

      The value.

  • WriteInt16(System.Int16)
    WriteInt16(System.Int16)
    WriteInt16(System.Int16)
    WriteInt16(System.Int16)

    Writes a 16-bit integer value to the output stream.

    public void WriteInt16(System.Int16)public void WriteInt16(System.Int16)Public Function WriteInt16(System.Int16) As void

    Parameters

    • value
      System.Int16
      System.Int16
      System.Int16
      System.Int16

      The value.

  • WriteInt32(System.Int32)
    WriteInt32(System.Int32)
    WriteInt32(System.Int32)
    WriteInt32(System.Int32)

    Writes a 32-bit integer value to the output stream.

    public void WriteInt32(System.Int32)public void WriteInt32(System.Int32)Public Function WriteInt32(System.Int32) As void

    Parameters

    • value
      System.Int32
      System.Int32
      System.Int32
      System.Int32

      The value.

  • WriteInt64(System.Int64)
    WriteInt64(System.Int64)
    WriteInt64(System.Int64)
    WriteInt64(System.Int64)

    Writes a 64-bit integer value to the output stream.

    public void WriteInt64(System.Int64)public void WriteInt64(System.Int64)Public Function WriteInt64(System.Int64) As void

    Parameters

    • value
      System.Int64
      System.Int64
      System.Int64
      System.Int64

      The value.

  • WriteSingle(System.Single)
    WriteSingle(System.Single)
    WriteSingle(System.Single)
    WriteSingle(System.Single)

    Writes a floating-point value to the output stream.

    public void WriteSingle(System.Single)public void WriteSingle(System.Single)Public Function WriteSingle(System.Single) As void

    Parameters

    • value
      System.Single
      System.Single
      System.Single
      System.Single

      The value.

  • WriteString(System.String)
    WriteString(System.String)
    WriteString(System.String)
    WriteString(System.String)

    Writes a string value to the output stream.

    public uint WriteString(System.String)public uint WriteString(System.String)Public Function WriteString(System.String) As uint

    Parameters

    • value
      System.String
      System.String
      System.String
      System.String

      The value.

    Returns

    • uint
      uint
      uint
      uint

      The length of the string, in bytes.

  • WriteTimeSpan(Windows.Foundation.TimeSpan)
    WriteTimeSpan(Windows.Foundation.TimeSpan)
    WriteTimeSpan(Windows.Foundation.TimeSpan)
    WriteTimeSpan(Windows.Foundation.TimeSpan)

    Writes a time-interval value to the output stream.

    public void WriteTimeSpan(Windows.Foundation.TimeSpan)public void WriteTimeSpan(Windows.Foundation.TimeSpan)Public Function WriteTimeSpan(Windows.Foundation.TimeSpan) As void

    Parameters

  • WriteUInt16(System.UInt16)
    WriteUInt16(System.UInt16)
    WriteUInt16(System.UInt16)
    WriteUInt16(System.UInt16)

    Writes a 16-bit unsigned integer value to the output stream.

    public void WriteUInt16(System.UInt16)public void WriteUInt16(System.UInt16)Public Function WriteUInt16(System.UInt16) As void

    Parameters

    • value
      System.UInt16
      System.UInt16
      System.UInt16
      System.UInt16

      The value.

  • WriteUInt32(System.UInt32)
    WriteUInt32(System.UInt32)
    WriteUInt32(System.UInt32)
    WriteUInt32(System.UInt32)

    Writes a 32-bit unsigned integer value to the output stream.

    public void WriteUInt32(System.UInt32)public void WriteUInt32(System.UInt32)Public Function WriteUInt32(System.UInt32) As void

    Parameters

    • value
      System.UInt32
      System.UInt32
      System.UInt32
      System.UInt32

      The value.

  • WriteUInt64(System.UInt64)
    WriteUInt64(System.UInt64)
    WriteUInt64(System.UInt64)
    WriteUInt64(System.UInt64)

    Writes a 64-bit unsigned integer value to the output stream.

    public void WriteUInt64(System.UInt64)public void WriteUInt64(System.UInt64)Public Function WriteUInt64(System.UInt64) As void

    Parameters

    • value
      System.UInt64
      System.UInt64
      System.UInt64
      System.UInt64

      The value.

Device family

Windows 10 (introduced v10.0.10240.0)

API contract

Windows.Foundation.UniversalApiContract (introduced v1)

Attributes

Windows.Foundation.Metadata.ActivatableAttribute
Windows.Foundation.Metadata.ThreadingAttribute
Windows.Foundation.Metadata.MarshalingBehaviorAttribute
Windows.Foundation.Metadata.ActivatableAttribute
Windows.Foundation.Metadata.ContractVersionAttribute

Details

Assembly

Windows.Storage.Streams.dll