OpenObject Method

Article
10/31/2008

OpenObject Method

The OpenObject method binds to and opens data from the specified object.

Syntax

Sub OpenObject(ByVal Source as Object, ByVal InterfaceName as String)
HRESULT OpenObject(IUnknown* Source, BSTR InterfaceName);

Parameters

Source
The object reference (interface) to the object to open.

InterfaceName
A string that indicates the type of interface passed in the first argument. Can be one of the following strings: IBodyPart, _Stream, IStream, and IMessage.

Remarks

You can use the IDataSource.OpenObject method to open messaging data from other objects that implement an appropriate interface; for example, you may have a message in serialized format that is contained within a Microsoft® ActiveX® Data Objects (ADO) Stream object. You can open the object and load the serialized message data into a Message object. Similarly, you can have the serial message data in an object that exposes the IStream, IBodyPart, and IMessage interfaces.

Note Circular binding is not supported. You cannot use OpenObject to open the same object, such as the following:

SameMsg.DataSource.OpenObject SameMsg, "IMessage"

Also, you cannot bind to BodyPart objects within the Message objects body part hierarchy. You must use a separate Message object.

One example how you can use the OpenObject method is the manipulation of encapsulated messages. A received message can contain a body part for which the ContentMediaType property is message. You might want to see the address of the sender and the subject of this encapsulated message but the body part object does not expose properties for these. You can create a new Message object and call the IDataSource.OpenObject method, passing the object reference of the encapsulated message body part. This effectively imports the contents of the encapsulated message into the Message object. You can then examine and manipulate the properties and contents of the message by using the new Message object. To save any changes you have made, you can call the IDataSource.Save method, and the modified message contents will be saved back to the source body part.

If you are using C++, do not pass the IStream interface to the OpenObject method if you want the interface that is returned by IDataSource.Source to be accessible to scripting languages.

If the interface name passed (the InterfaceName) is not recognized, the method raises an exception.

After a successful call to OpenObject, the IDataSource.SourceClass property returns the interface name specified by the InterfaceName parameter. Likewise, the IDataSource.Source property returns the object reference specified by the Source property.

Example

' Reference to Microsoft ActiveX Data Objects 2.5 Library
' Reference to Microsoft CDO for Windows 2000 Library
Function LoadMessageFromFile(Path As String) As Message
    Dim Stm As New Stream
    Stm.Open
    Stm.LoadFromFile Path
    Dim iMsg As New CDO.Message
    Dim iDsrc As IDataSource
    Set iDsrc = iMsg
    iDsrc.OpenObject Stm, "_Stream"
    Set LoadMessageFromFile = iMsg
End Function

Function ExtractMessage(iBp As IBodyPart) As Message
    Dim iMsg As New CDO.Message
    Dim iDsrc As IDataSource
    Set iDsrc = iMsg
    iDsrc.OpenObject iBp, "IBodyPart"
    Set ExtractMessage = iMsg
End Function
IMessagePtr ExtractMessage(IBodyPartPtr iBp)
{
      IMessagePtr iMsg(__uuidof(Message));
      IDataSourcePtr iDsrc;
      iDsrc = iMsg;

      try
      {
            iDsrc->OpenObject(iBp,_bstr_t("IBodyPart"));
      }
      catch(_com_error error)
      {
            throw error;
      }
      return iMsg;

}

IMessagePtr Load_Message_from_File(_bstr_t path)
{
      /*
      ** This example shows a common use of the ADO Stream
      ** object with CDO, namely, opening a serialized
      ** message from a file on disk and loading it into
      ** a CDO Message object.
      **/

      _StreamPtr  pStm(__uuidof(Stream));
      _variant_t varOptional(DISP_E_PARAMNOTFOUND,VT_ERROR);
      try {
            pStm->raw_Open(
                            varOptional,
                            adModeUnknown,
                            adOpenStreamUnspecified,
                            NULL,
                            NULL);
            pStm->LoadFromFile(path);
      }
      catch(_com_error e)
      {
            throw e;
      }

      IMessagePtr iMsg(__uuidof(Message));
      IDataSourcePtr iDsrc;
      iDsrc = iMsg;

      try {
            iDsrc->OpenObject(pStm,_bstr_t("_Stream"));
      }
      catch(_com_error e)
      {
            throw e;
      }
      return iMsg;
}

Sub EmbedMessage(iMsg As CDO.Message, iBp As IBodyPart)
    Dim iDsrc
    Set iDsrc = iMsg.DataSource
    iDsrc.SaveToObject iBp, "IBodyPart"
End Sub

Function ExtractMessage(iBp As IBodyPart) As Message
    Dim iMsg
    Set iMsg = CreateObject("CDO.Message")
    Dim iDsrc
    Set iDsrc = iMsg.DataSource
    iDsrc.OpenObject iBp, "IBodyPart"
    Set ExtractMessage = iMsg
End Function

Function LoadMessageFromFile(Path) As Message
    Dim Stm
    Set Stm = CreateObject("ADODB.Stream")
    Stm.Open
    Stm.LoadFromFile Path
    Dim iMsg
    Set iMsg = CreateObject("CDO.Message")
    Dim iDsrc
    Set iDsrc = iMsg
    iDsrc.OpenObject Stm, "_Stream"
    Set LoadMessageFromFile = iMsg
End Function

Sub SaveMessageToFile(iMsg, Filepath)
    Dim Stm
    Set Stm = CreateObject("ADODB.Stream")
    Stm.Open
    Stm.Type = adTypeText ' 2
    Stm.Charset = "US-ASCII"

    Dim iDsrc
    Set iDsrc = iMsg.DataSource
    iDsrc.SaveToObject Stm, "_Stream"

    Stm.SaveToFile Filepath, adSaveCreateOverWrite

End Sub

OpenObject Method