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TransferEncoding Enumeration

Specifies the Content-Transfer-Encoding header information for an e-mail message attachment.

Namespace: System.Net.Mime
Assembly: System (in system.dll)

Public Enumeration TransferEncoding
Dim instance As TransferEncoding

public enum TransferEncoding
public enum TransferEncoding

 Member nameDescription
Base64Encodes stream-based data. See RFC 2406 Section 6.8. 
QuotedPrintableEncodes data that consists of printable characters in the US-ASCII character set. See RFC 2406 Section 6.7. 
SevenBitUsed for data that is not encoded. The data is in 7-bit US-ASCII characters with a total line length of no longer than 1000 characters. See RFC2406 Section 2.7. 
UnknownIndicates that the transfer encoding is unknown. 

The values in the TransferEncoding enumeration are used with the AttachmentBase.TransferEncoding property.

The Content-Transfer-Encoding header specifies the encoding of the associated message body so that it meets SMTP requirements. SMTP requires data for transport to be in 7-bit US-ASCII characters with lines no longer than 1000 characters.

Content-Transfer-Encoding values are described in detail in RFC 2045 Section 6, available at

The following code example displays TransferEncoding used by an attachment.

public static void DisplayStreamAttachment(Attachment a)
    Stream s = a.ContentStream;
    StreamReader reader = new StreamReader(s);
    Console.WriteLine("Content: {0}", reader.ReadToEnd());
    Console.WriteLine("Content Type {0}", a.ContentType.ToString());
    Console.WriteLine("Transfer Encoding {0}", a.TransferEncoding);
    // Note that you cannot close the reader before the e-mail is sent. 
    // Closing the reader before sending the e-mail will close the 
    // ContentStream and cause an SmtpException.
    reader = null;

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0