Creating a Message Attachment

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A message attachment is some additional data, such as a file, another message, or an OLE object, that you can send or save along with a message. Each attachment has a collection of properties that identifies it and describes its type and how it is rendered. Like recipients, message attachments can only be accessed through the message to which they belong. Therefore, for an attachment to be usable, its message must be open.

To create a message attachment

1. Call the message's IMessage::CreateAttach method and pass NULL as the interface identifier. CreateAttach returns a number that uniquely identifies the new attachment within the message. The attachment number is stored in the PR_ATTACH_NUM (PidTagAttachNumber) property and is valid only as long as the message containing the attachment is open.

2. Call IMAPIProp::SetProps to set PR_ATTACH_METHOD (PidTagAttachMethod) to indicate how to access the attachment. PR_ATTACH_METHOD is required. Set it to:

   • ATTACH_BY_VALUE if the attachment is binary data.

   • ATTACH_BY_REFERENCE, ATTACH_BY_REF_RESOLVE, or ATTACH_BY_REF_ONLY if the attachment is a file.

   • ATTACH_EMBEDDED_MSG if the attachment is a message.

   • ATTACH_OLE if the attachment is an OLE object.

3. Set the appropriate attachment data property:

   • PR_ATTACH_DATA_BIN (PidTagAttachDataBinary) for binary data and OLE 1 objects.

   • PR_ATTACH_PATHNAME (PidTagAttachPathname) for files.

   • PR_ATTACH_DATA_OBJ (PidTagAttachDataObject) for messages and OLE 2 objects.

4. Set PR_ATTACH_RENDERING (PidTagAttachRendering) to hold the graphic representation of the attachment for file or binary attachments. Do not set it for OLE objects, which store the rendering information internally, or for attached messages.

5. Set PR_RENDERING_POSITION (PidTagRenderingPosition) to indicate where the attachment should be displayed. PR_RENDERING_POSITION applies only to clients that set the PR_BODY property. If you only support PR_RTF_COMPRESSED, place the following placeholder information in the compressed stream:

   \objattph
   
   

   To set PR_RENDERING_POSITION, assign either a number that represents an ordinal offset in characters, with the first character of PR_BODY being 0, if you need to know where in the message the attachment is rendered, or 0xFFFFFFFF, if you do not render attachments within PR_BODY.

6. Set PR_ATTACH_FILENAME (PidTagAttachFilename) to indicate the short name of the file for a file attachment and PR_ATTACH_LONG_FILENAME (PidTagAttachLongFilename) to indicate the name of the file as supported on a platform that handles the long filename format. Both properties are optional. However, if you set PR_ATTACH_LONG_FILENAME, also set PR_ATTACH_FILENAME.

7. Set PR_DISPLAY_NAME (PidTagDisplayName) to indicate the name for the attachment that can appear in a dialog box. PR_DISPLAY_NAME is optional.

To set PR_ATTACH_DATA_BIN

1. Call IMAPIProp::OpenProperty to open the property with the IStream interface.

2. If a file contains the data and it is open or if you need explicit control over buffer size, call IStream::Write in a loop to place the data in the stream.

3. Another option is to call OpenStreamOnFile to create a stream to access the data file and then call this stream's IStream::CopyTo method to copy the data to the stream returned by OpenProperty.

4. Call the new stream's IStream::Commit method.

To set PR_ATTACH_DATA_OBJ

1. Call IMAPIProp::OpenProperty to open the property with the IStreamDocfile interface to create a stream that works with structured storage. IStreamDocfile is implemented by message store providers to give clients a higher-performance way to store and retrieve structured storage. The IStreamDocfile interface is the same as IStream, but the content of the stream is guaranteed to be formatted as structured storage. If this call succeeds, create the stream with the same steps outlined for setting PR_ATTACH_DATA_BIN.

2. If OpenProperty fails:

   1. Call OpenProperty again asking for IStorage.

   2. Call StgOpenStorage to open the OLE object and return a storage object.

   3. Call the returned storage object's IStorage::CopyTo method to copy to the storage object returned from OpenProperty.

   4. Call the new storage object's IStorage::Commit method.

To set PR_ATTACH_PATHNAME

1. Allocate an SPropValue structure, setting the ulPropTag member to PR_ATTACH_PATHNAME and the Value.LPSZ member to the character string that represents the filename.

2. Call the attachment's IMAPIProp::SetProps method.

Note
If your platform supports long filenames, set both PR_ATTACH_PATHNAME and PR_ATTACH_LONG_PATHNAME. It might be necessary to make an operating system call to retrieve the short filename.

See Also

Concepts

MAPI Attachments