ADO Stream Object

The ActiveX Data Object(ADO) Stream object provides access to a stream of text data or binary data. By access, we mean the ability to write ,read, and manage the stream.

A buffer area from which the content of the Stream can be read. The nature of the contents of a Stream could be text or binary type of information, although Microsoft documentation mentions just the binary part.

We can obtained a Stream object by three ways:

1. From a URL pointing to an object containing text data or binary data. This object can be a simple document, a Record object representing a structured document, or a folder.

2. By opening the default ADO Stream object associated with a Record object. You can obtain the default stream associated with the Record object when the Record is opened, to eliminate a round-trip just to open the stream.

3. By instantiating a ADO Stream object. These Stream objects can be used to store records or data for the purposes of our application. Unlike a Stream associated with the URL, or the default Stream of the Records, an instantiated Stream has no association with an underlying source by default.

Use the ADO Stream object to access an item's stream.

For example:

Dim Stm As ADODB.Stream
Dim Rec as New ADODB.Record
Dim Conn as New ADODB.Connection
Dim Stm2 as New ADODB.Stream
Dim Url As String

Url = "http://server/public/dataitem.txt"

Conn.Provider = "ExOLEDB.DataSource"
Conn.Open Url
Rec.Open Url, Conn
Set Stm = Rec.Fields(adDefaultStream).Value
' Or, alternately
Stm2.Open Rec, adModeRead, adOpenStreamFromRecord

'...
Conn.Close
Rec.Close
Stm.Close
Stm2.Close
Set Conn = Nothing
Set Rec = Nothing
Set Stm = Nothing
Set Stm2 = Nothing

Properties of ADO Stram Object.

Property	Description
CharSet	Sets or returns a value that specifies into which character set the contents are to be translated. This property is only used with text Stream objects (type is adTypeText)
EOS	Returns whether the current position is at the end of the stream or not
LineSeparator	Sets or returns the line separator character used in a text Stream object
Mode	Sets or returns the available permissions for modifying data
Position	Sets or returns the current position (in bytes) from the beginning of a Stream object
Size	Returns the size of an open Stream object
State	Returns a value describing if the Stream object is open or closed
Type	Sets or returns the type of data in a Stream object

Methods of ADO Stram Object.

Methods	Description
Cancel	Cancels an execution of an Open call on a Stream object
Close	Closes a Stream object
CopyTo	Copies a specified number of characters/bytes from one Stream object into another Stream object
Flush	Sends the contents of the Stream buffer to the associated underlying object
LoadFromFile	Loads the contents of a file into a Stream object
Open	Opens a Stream object
Read	Reads the entire stream or a specified number of bytes from a binary Stream object
ReadText	Reads the entire stream, a line, or a specified number of characters from a text Stream object
SaveToFile	Saves the binary contents of a Stream object to a file
SetEOS	Sets the current position to be the end of the stream (EOS)
SkipLine	Skips a line when reading a text Stream
Write	Writes binary data to a binary Stream object
WriteText	Writes character data to a text Stream object