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XmlWriter.WriteBase64 Method

When overridden in a derived class, encodes the specified binary bytes as Base64 and writes out the resulting text.

Namespace:  System.Xml
Assembly:  System.Xml (in System.Xml.dll)

public abstract void WriteBase64(
	byte[] buffer,
	int index,
	int count
)

Parameters

buffer
Type: System.Byte[]

Byte array to encode.

index
Type: System.Int32

The position in the buffer indicating the start of the bytes to write.

count
Type: System.Int32

The number of bytes to write.

ExceptionCondition
ArgumentNullException

buffer is null.

ArgumentOutOfRangeException

index or count is less than zero.

-or-

The buffer length minus index is less than count.

InvalidOperationException

An XmlWriter method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.”

For example, the byte buffer may contain the binary contents of a GIF image. This clearly would not be valid XML. The Base64 encoding is designed to represent arbitrary byte sequences in a text form comprised of the 65 US-ASCII characters ([A-Za-z0-9+/=]) where each character encodes 6 bits of the binary data. For more information, see Requests for Comments (RFC) 1521 located on the Request for Comments Web site at http://www.rfc-editor.org/.

For the asynchronous version of this method, see WriteBase64Async.

The following example uses the WriteBase64 method to write Base64 data. The Base64 data is embedded within an <image> element.


public static void Base64EncodeImageFile() {

  int bufferSize = 1000;
  byte[] buffer = new byte[bufferSize];
  int readBytes = 0;
	
  using (XmlWriter writer = XmlWriter.Create("output.xml")) {

       FileStream inputFile = new FileStream(@"C:\artFiles\sunset.jpg",
                                                                    FileMode.OpenOrCreate, FileAccess.Read, FileShare.Read);
       writer.WriteStartDocument();
       writer.WriteStartElement("image");
       BinaryReader br = new BinaryReader(inputFile);
       Console.WriteLine("\r\nWriting Base64 data...");

       do {
          readBytes = br.Read(buffer, 0, bufferSize);
          writer.WriteBase64(buffer, 0, readBytes);
       } while (bufferSize <= readBytes);
       br.Close();
		
    writer.WriteEndElement();// </image>
    writer.WriteEndDocument();
		
  }
}

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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