GetItemDataStream Method (ZipWriter)

In This Topic

Returns a new Stream object that implements a write-only stream around the WriteItemData method.

Syntax

Visual Basic
C#

'Declaration
 
Public Function GetItemDataStream() As Stream

'Usage
 
Dim instance As ZipWriter
Dim value As Stream
 
value = instance.GetItemDataStream()

public Stream GetItemDataStream()

Return Value

A write-only System.IO.Stream object.

Remarks

The method creates a new write-only, non-seeking stream object based on the ZipWriter instance's current item. Each call to the stream's Stream.Write method will call WriteItemData.

The method allows you to use the Stream class interface to write item data into ZipWriter instead of using WriteItemData directly. This makes it possible to integrate ZipWriter with
other classes that use the Stream class interface without the need for "glue code."

Dispose should be called on the stream when all the current item's data has been written.

The stream returned by the method should be considered unique to the current item. This means you should not reuse the stream with later items. Instead, get a new stream instance by calling the method again. The example below illustrates this.

WriteItemData can still be called to write data even if this method is used. This can be done after the stream returned by the method has been closed or even while the stream is active.

The method can be used to create nested zip archives with ZipWriter. A nested zip archive is when an item in an archive is another zip archive. By providing the stream returned by the method to a new instance of ZipWriter, a nested zip archive will be created. See this page for an example.

Example

The following examples show how to create a ZipWriter instance that will write into a stream that has been prepared.

C#
VB.NET

static void Example()
{
  string zipFilePath = @"D:\RealTimeZipExamples\MyZipFile.zip";

  // Create a stream for a new zip file
  using( FileStream zipFileStream = new FileStream( zipFilePath, FileMode.Create, FileAccess.Write, FileShare.None ) )
  {
    // Create a ZipWriter instance that will write into a stream that has been prepared
    using( ZipWriter writer = new ZipWriter( zipFileStream ) )
    {
      ZipItemLocalHeader header = new ZipItemLocalHeader();

      header.FileName = "File1.xml";
      writer.WriteItemLocalHeader( header );

      // Instead of using WriteItemData(), we will get a writing stream to the item's data 
      using( Stream itemStream = writer.GetItemDataStream() )
      {
        // The stream will be 'closed' automatically by the 'using' statement. This will not 
        // close the zip file or the current item. It will only indicate to the stream 
        // that its work is done and clear its resources. 

        // Having a stream object handy here makes using a XmlWriter very easy 
        using( XmlWriter xml = XmlWriter.Create( itemStream ) )
        {
          xml.WriteStartDocument();
          xml.WriteStartElement( "SomeType" );
          xml.WriteElementString( "ID", "Something" );
          xml.WriteEndElement();
          xml.WriteEndDocument();
        }
      }

      header.FileName = "File2.xml";
      writer.WriteItemLocalHeader( header );
      using( Stream itemStream = writer.GetItemDataStream() )
      {
        using( XmlWriter xml = XmlWriter.Create( itemStream ) )
        {
          xml.WriteStartDocument();
          xml.WriteStartElement( "SomeOtherType" );

          byte[] someData = new byte[] { 12, 45, 67, 35, 67, 255, 255, 45 };

          // This is legal 
          writer.WriteItemData( someData );

          xml.WriteEndElement();
          xml.WriteEndDocument();
        }
      }

      byte[] someOtherData = new byte[] { 6, 34, 56, 108, 127, 98, 44, 35, 67, 255, 255, 45 };

      // This is also legal 
      writer.WriteItemData( someOtherData );
    }
  }
}

Private Shared Sub Example()
  Dim zipFilePath As String = "D:\RealTimeZipExamples\MyZipFile.zip"

  ' Create a stream for a new zip file
  Using zipFileStream As New FileStream(zipFilePath, FileMode.Create, FileAccess.Write, FileShare.None)
    ' Create a ZipWriter instance that will write into a stream that has been prepared
    Using writer As New ZipWriter(zipFileStream)
      Dim header As New ZipItemLocalHeader()

      header.FileName = "File1.xml"
      writer.WriteItemLocalHeader(header)

      ' Instead of using WriteItemData(), we will get a writing stream to the item's data 
      Using itemStream As Stream = writer.GetItemDataStream()
        ' The stream will be 'closed' automatically by the 'using' statement. This will not 
        ' close the zip file or the current item. It will only indicate to the stream 
        ' that its work is done and clear its resources. 

        ' Having a stream object handy here makes using a XmlWriter very easy 
        Using xml As XmlWriter = XmlWriter.Create(itemStream)
          xml.WriteStartDocument()
          xml.WriteStartElement("SomeType")
          xml.WriteElementString("ID", "Something")
          xml.WriteEndElement()
          xml.WriteEndDocument()
        End Using
      End Using

      header.FileName = "File2.xml"
      writer.WriteItemLocalHeader(header)
      Using itemStream As Stream = writer.GetItemDataStream()
        Using xml As XmlWriter = XmlWriter.Create(itemStream)
          xml.WriteStartDocument()
          xml.WriteStartElement("SomeOtherType")

          Dim someData() As Byte = {12, 45, 67, 35, 67, 255, 255, 45}

          ' This is legal 
          writer.WriteItemData(someData)

          xml.WriteEndElement()
          xml.WriteEndDocument()
        End Using
      End Using

      Dim someOtherData() As Byte = {6, 34, 56, 108, 127, 98, 44, 35, 67, 255, 255, 45}

      ' This is also legal 
      writer.WriteItemData(someOtherData)
    End Using
  End Using
End Sub

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

ZipWriter Class
ZipWriter Members

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