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The Item Default Stream Property

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The Item Default Stream Property

This content is no longer actively maintained. It is provided as is, for anyone who may still be using these technologies, with no warranties or claims of accuracy with regard to the most recent product version or service release.

Each item in the Exchange store that is not a collection has a special property called the default stream. This property contains any sequence of characters or bytes of any length, just like a file on the file system. At first glance, the stream for an item might appear to be equivalent to another property whose type is text or binary. The primary differences are as follows:

  • The default stream for an item is always available using the same name or index, regardless of the item.
  • The stream can contain a sequence of characters or bytes of any length. Regular text or binary properties have limited size. Text properties can be up to 50 kilobytes (KB).
  • Only the item's stream is available through the Microsoft® Win32® file system application programming interfaces (APIs). In this way, item default streams are the same as the contents of a file on the file system.

When using Microsoft ActiveX® Data Objects (ADO) or Collaboration Data Objects (CDO), you access the item's stream by requesting the property with the value adDefaultStream in the Fields collection. The returned Field object contains a reference to an ADO Stream object (_Stream interface). With OLE DB, the property is requested using the DBGUID_DEFAULTSTREAM flag. The stream is accessed using the returned IStream interface reference. The ADO Stream object differentiates between binary and text streams. No differentiation exists when using the raw IStream interface.

No inherent relationship exists between an item's properties and its stream, with the exception of messages and Microsoft Office documents.

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Build: June 2007 (2007.618.1)

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