Assembly: System.Xml (in system.xml.dll)
'Declaration Public Overridable Function ReadElementContentAsBase64 ( _ buffer As Byte(), _ index As Integer, _ count As Integer _ ) As Integer 'Usage Dim instance As XmlReader Dim buffer As Byte() Dim index As Integer Dim count As Integer Dim returnValue As Integer returnValue = instance.ReadElementContentAsBase64(buffer, index, count)
public function ReadElementContentAsBase64 ( buffer : byte, index : int, count : int ) : int
The buffer into which to copy the resulting text. This value cannot be a null reference (Nothing in Visual Basic).
The offset into the buffer where to start copying the result.
The maximum number of bytes to copy into the buffer. The actual number of bytes copied is returned from this method.
Return ValueThe number of bytes written to the buffer.
The buffer value is a null reference (Nothing in Visual Basic).
The current node is not an element node.
The index into the buffer or index + count is larger than the allocated buffer size.
The XmlReader implementation does not support this method.
The element contains mixed-content.
The content cannot be converted to the requested type.
This method reads the element content, decodes it using Base64 encoding, and returns the decoded binary bytes (for example, an inline Base64-encoded GIF image) into the buffer. For more information, see RFC 1521, "MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies". You can obtain RFCs from the Request for Comments Web site at http://www.rfc-editor.org.
ReadElementContentAsBase64 can only read simple-content elements. The element can contain text, white space, significant white space, CDATA sections, comments and processing instructions. It can also contain entity references, which are automatically expanded. The element cannot have child elements.
This method is very similar to the ReadContentAsBase64 method except that it can only be called on element node types.
If the count value is higher than the number of bytes in the document, or if it is equal to the number of bytes in the document, the XmlReader reads all the remaining bytes in the document and returns the number of bytes read. The next XmlReader method call returns a zero and moves the reader to the node following the EndElement.
If you call Read before all of the element content is consumed, the reader may behave as if the first content was consumed and then the Read method was called. This means that the reader will read all the text until the end element is encountered. It will then read the end tag node, read the next node, and then position itself on the next subsequent node.
The following example reads an inline Base64 encoded image. The Base64 data is embedded within the <image> element. A BinaryWriter is used to create a new binary data file.
Public Shared Sub Base64DecodeImageFile() Dim buffer(999) As Byte Dim readBytes As Integer = 0 Using reader As XmlReader = XmlReader.Create("output.xml") Dim outputFile As New FileStream("C:\artFiles\data\newImage.jpg", FileMode.OpenOrCreate, FileAccess.Write, FileShare.Write) ' Read to the image element. reader.ReadToFollowing("image") ' Read the Base64 data. Console.WriteLine(vbCr + vbLf + "Reading Base64...") Dim bw As New BinaryWriter(outputFile) readBytes = reader.ReadElementContentAsBase64(buffer, 0, 50) While (readBytes > 0) bw.Write(buffer, 0, readBytes) readBytes = reader.ReadElementContentAsBase64(buffer, 0, 50) End While outputFile.Close() End Using End Sub 'Base64DecodeImageFile
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.