DataReader DataReader DataReader DataReader Class

Reads data from an input stream.

Syntax

Declaration

public sealed class DataReaderpublic sealed class DataReaderPublic NotInheritable Class DataReaderpublic sealed class DataReader

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 reader.

Properties summary

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

Gets or sets the read options for the input stream.

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

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

Methods summary

Closes the current stream and releases system resources.

Detaches the buffer that is associated with the data reader.

Detaches the stream that is associated with the data reader.

Creates a new instance of the data reader with data from the specified buffer.

Loads data from the input stream.

Reads a Boolean value from the input stream.

Reads a buffer from the input stream.

Reads a byte value from the input stream.

Reads an array of byte values from the input stream.

Reads a date and time value from the input stream.

Reads a floating-point value from the input stream.

Reads a GUID value from the input stream.

Reads a 16-bit integer value from the input stream.

Reads a 32-bit integer value from the input stream.

Reads a 64-bit integer value from the input stream.

Reads a floating-point value from the input stream.

Reads a string value from the input stream.

Reads a time-interval value from the input stream.

Reads a 16-bit unsigned integer from the input stream.

Reads a 32-bit unsigned integer from the input stream.

Reads a 64-bit unsigned integer from the input stream.

Constructors

  • DataReader(IInputStream)
    DataReader(IInputStream)
    DataReader(IInputStream)
    DataReader(IInputStream)

    Creates and initializes a new instance of the data reader.

    public DataReader(IInputStream inputStream)public New(IInputStream inputStream)Public Sub New(inputStream As IInputStream)public DataReader(IInputStream inputStream)

    Parameters

Properties

  • ByteOrder
    ByteOrder
    ByteOrder
    ByteOrder

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

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

    Property Value

  • InputStreamOptions
    InputStreamOptions
    InputStreamOptions
    InputStreamOptions

    Gets or sets the read options for the input stream.

    public InputStreamOptions InputStreamOptions { get; set; }public InputStreamOptions InputStreamOptions { get; set; }Public ReadWrite Property InputStreamOptions As InputStreamOptionspublic InputStreamOptions InputStreamOptions { get; set; }

    Property Value

  • UnconsumedBufferLength
    UnconsumedBufferLength
    UnconsumedBufferLength
    UnconsumedBufferLength

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

    public uint UnconsumedBufferLength { get; }public uint UnconsumedBufferLength { get; }Public ReadOnly Property UnconsumedBufferLength As uintpublic uint UnconsumedBufferLength { get; }

    Property Value

    • uint
      uint
      uint
      uint

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

  • UnicodeEncoding
    UnicodeEncoding
    UnicodeEncoding
    UnicodeEncoding

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

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

    Property Value

Methods

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

    Closes the current stream and releases system resources.

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

    Remarks

    DataReader 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 DataReader 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 reader.

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

    Returns

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

    Detaches the stream that is associated with the data reader.

    public IInputStream DetachStream()public IInputStream DetachStream()Public Function DetachStream() As IInputStreampublic IInputStream DetachStream()

    Returns

  • FromBuffer(IBuffer)
    FromBuffer(IBuffer)
    FromBuffer(IBuffer)
    FromBuffer(IBuffer)

    Creates a new instance of the data reader with data from the specified buffer.

    public static DataReader FromBuffer(IBuffer buffer)public static DataReader FromBuffer(IBuffer buffer)Public Static Function FromBuffer(buffer As IBuffer) As DataReaderpublic static DataReader FromBuffer(IBuffer buffer)

    Parameters

    Returns

  • LoadAsync(UInt32)
    LoadAsync(UInt32)
    LoadAsync(UInt32)
    LoadAsync(UInt32)

    Loads data from the input stream.

    public DataReaderLoadOperation LoadAsync(UInt32 count)public DataReaderLoadOperation LoadAsync(UInt32 count)Public Function LoadAsync(count As UInt32) As DataReaderLoadOperationpublic DataReaderLoadOperation LoadAsync(UInt32 count)

    Parameters

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

      The count of bytes to load into the intermediate buffer.

    Returns

    Remarks

    The read operation can get more or fewer bytes depending on how the InputStreamOptions property is set.

  • ReadBoolean()
    ReadBoolean()
    ReadBoolean()
    ReadBoolean()

    Reads a Boolean value from the input stream.

    public bool ReadBoolean()public bool ReadBoolean()Public Function ReadBoolean() As boolpublic bool ReadBoolean()

    Returns

    • bool
      bool
      bool
      bool

      The value.

  • ReadBuffer(UInt32)
    ReadBuffer(UInt32)
    ReadBuffer(UInt32)
    ReadBuffer(UInt32)

    Reads a buffer from the input stream.

    public IBuffer ReadBuffer(UInt32 length)public IBuffer ReadBuffer(UInt32 length)Public Function ReadBuffer(length As UInt32) As IBufferpublic IBuffer ReadBuffer(UInt32 length)

    Parameters

    • length
      System.UInt32
      System.UInt32
      System.UInt32
      System.UInt32

      The length of the buffer, in bytes.

    Returns

  • ReadByte()
    ReadByte()
    ReadByte()
    ReadByte()

    Reads a byte value from the input stream.

    public byte ReadByte()public byte ReadByte()Public Function ReadByte() As bytepublic byte ReadByte()

    Returns

    • byte
      byte
      byte
      byte

      The value.

  • ReadBytes(Byte[])
    ReadBytes(Byte[])
    ReadBytes(Byte[])
    ReadBytes(Byte[])

    Reads an array of byte values from the input stream.

    public void ReadBytes(Byte[] value)public void ReadBytes(Byte[] value)Public Function ReadBytes(value As Byte[]) As voidpublic void ReadBytes(Byte[] value)

    Parameters

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

      The array that receives the byte values.

  • ReadDateTime()
    ReadDateTime()
    ReadDateTime()
    ReadDateTime()

    Reads a date and time value from the input stream.

    public DateTime ReadDateTime()public DateTimeOffset ReadDateTime()Public Function ReadDateTime() As DateTimeOffsetpublic DateTime ReadDateTime()

    Returns

  • ReadDouble()
    ReadDouble()
    ReadDouble()
    ReadDouble()

    Reads a floating-point value from the input stream.

    public double ReadDouble()public double ReadDouble()Public Function ReadDouble() As doublepublic double ReadDouble()

    Returns

    • double
      double
      double
      double

      The value.

  • ReadGuid()
    ReadGuid()
    ReadGuid()
    ReadGuid()

    Reads a GUID value from the input stream.

    public Guid ReadGuid()public Guid ReadGuid()Public Function ReadGuid() As Guidpublic Guid ReadGuid()

    Returns

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

      The value.

  • ReadInt16()
    ReadInt16()
    ReadInt16()
    ReadInt16()

    Reads a 16-bit integer value from the input stream.

    public short ReadInt16()public short ReadInt16()Public Function ReadInt16() As shortpublic short ReadInt16()

    Returns

    • short
      short
      short
      short

      The value.

  • ReadInt32()
    ReadInt32()
    ReadInt32()
    ReadInt32()

    Reads a 32-bit integer value from the input stream.

    public int ReadInt32()public int ReadInt32()Public Function ReadInt32() As intpublic int ReadInt32()

    Returns

    • int
      int
      int
      int

      The value.

  • ReadInt64()
    ReadInt64()
    ReadInt64()
    ReadInt64()

    Reads a 64-bit integer value from the input stream.

    public long ReadInt64()public long ReadInt64()Public Function ReadInt64() As longpublic long ReadInt64()

    Returns

    • long
      long
      long
      long

      The value.

  • ReadSingle()
    ReadSingle()
    ReadSingle()
    ReadSingle()

    Reads a floating-point value from the input stream.

    public float ReadSingle()public float ReadSingle()Public Function ReadSingle() As floatpublic float ReadSingle()

    Returns

    • float
      float
      float
      float

      The value.

  • ReadString(UInt32)
    ReadString(UInt32)
    ReadString(UInt32)
    ReadString(UInt32)

    Reads a string value from the input stream.

    public string ReadString(UInt32 codeUnitCount)public string ReadString(UInt32 codeUnitCount)Public Function ReadString(codeUnitCount As UInt32) As stringpublic string ReadString(UInt32 codeUnitCount)

    Parameters

    • codeUnitCount
      System.UInt32
      System.UInt32
      System.UInt32
      System.UInt32

      The length of the string.

    Returns

    • string
      string
      string
      string

      The value.

  • ReadTimeSpan()
    ReadTimeSpan()
    ReadTimeSpan()
    ReadTimeSpan()

    Reads a time-interval value from the input stream.

    public TimeSpan ReadTimeSpan()public TimeSpan ReadTimeSpan()Public Function ReadTimeSpan() As TimeSpanpublic TimeSpan ReadTimeSpan()

    Returns

  • ReadUInt16()
    ReadUInt16()
    ReadUInt16()
    ReadUInt16()

    Reads a 16-bit unsigned integer from the input stream.

    public ushort ReadUInt16()public ushort ReadUInt16()Public Function ReadUInt16() As ushortpublic ushort ReadUInt16()

    Returns

    • ushort
      ushort
      ushort
      ushort

      The value.

  • ReadUInt32()
    ReadUInt32()
    ReadUInt32()
    ReadUInt32()

    Reads a 32-bit unsigned integer from the input stream.

    public uint ReadUInt32()public uint ReadUInt32()Public Function ReadUInt32() As uintpublic uint ReadUInt32()

    Returns

    • uint
      uint
      uint
      uint

      The value.

  • ReadUInt64()
    ReadUInt64()
    ReadUInt64()
    ReadUInt64()

    Reads a 64-bit unsigned integer from the input stream.

    public ulong ReadUInt64()public ulong ReadUInt64()Public Function ReadUInt64() As ulongpublic ulong ReadUInt64()

    Returns

    • ulong
      ulong
      ulong
      ulong

      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.ContractVersionAttribute
Windows.Foundation.Metadata.MarshalingBehaviorAttribute
Windows.Foundation.Metadata.StaticAttribute
Windows.Foundation.Metadata.ThreadingAttribute

Details

Assembly

Windows.Storage.Streams.dll