Поделиться через

Rendering an Attachment in Plain Text

  • Статья

This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This page may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist.

To render an attachment in a message with plain text, retrieve the attachment's PR_RENDERING_POSITION (PidTagRenderingPosition) property and apply it to the data in the PR_ATTACH_RENDERING (PidTagAttachRendering) property. There are two ways to retrieve PR_RENDERING_POSITION:

  • Open the attachment by calling the message's IMessage::OpenAttach method and then ask for the PR_RENDERING_POSITION property by calling the attachment's IMAPIProp::GetProps method. For more information, see IMessage::OpenAttach and IMAPIProp::GetProps.

  • Call the message's IMessage::GetAttachmentTable method to access its attachment table and retrieve the column that holds the PR_RENDERING_POSITION property. This way is always preferable. For more information, see IMessage::GetAttachmentTable.

Keep in mind that many RTF-aware message stores do not calculate PR_RENDERING_POSITION until a client requests the PR_BODY (PidTagBody) property of a message. Until that time, PR_RENDERING_POSITION usually represents an approximate value. Message store providers are allowed to supply clients with an approximate value to enhance performance.

The rendering for a file or binary attachment is stored in its PR_ATTACH_RENDERING property. You have the choice of retrieving PR_ATTACH_RENDERING in the same ways as you retrieved PR_RENDERING_POSITION: directly from the attachment or from the attachment table. For PR_ATTACH_RENDERING, the first strategy, although more time-consuming, is safer. Because some message store providers truncate their table columns to 255 bytes, or in a few cases 510 bytes, it is difficult to be sure that the PR_ATTACH_RENDERING column contains the complete rendering. When retrieving the property directly from the attachment, it will always be complete.

Neither OLE nor message attachments set PR_ATTACH_RENDERING. Instead, rendering information for OLE 1 attachments is stored in the message text stream. For OLE 2 attachments, it is stored in a special child stream of the storage object. Rendering information for message attachments is available through the form manager.

To retrieve the rendering for a message attachment

  1. Use the message class of the message to access the form manager.

  2. Access the form manager's PR_MINI_ICON property. For more information, see PR_MINI_ICON (PidTagMiniIcon).