Visual Basic Code Example: Time Sent Filters
This example provides a private Sub procedure that retrieves all the messages in a queue that were sent at a specific time. Filtering is done by peeking at the MSMQMessage.SentTime property of each message in the queue and removing only those messages sent at the specified time.
To filter messages by sent time
Declare the objects needed to read the messages in the queue.
|When declaring the MSMQMessage object when reading messages, the New keyword cannot be used.|
Obtain an MSMQQueueInfo object. The following example initializes the MSMQQueueInfo object by setting the MSMQQueueInfo.PathName property using the computer name and queue name provided by the caller.
Because this procedure sets the MSMQQueueInfo.PathName property of the MSMQQueueInfo object, Message Queuing must obtain the format name of the queue before opening the queue. The format name of a public queue must be retrieved from the directory service, and the format name of a local private queue can be obtained from information stored on the local computer. However, a remote private queue cannot be opened unless the MSMQQueueInfo.FormatName property is set with a direct format name. This procedure can be modified to receive the format name from the caller or to generate a direct format name. The applicable format name can then be used to set the FormatName property. For more information, see Format Names.
Call MSMQQueueInfo.Open to open the queue with receive access. When opening a queue with receive access the application can peek at or retrieve the messages in the queue.
Call MSMQQueue.PeekCurrent to initialize the cursor. This call points the cursor to the first message in the queue.
Using a loop, filter out messages with specified sent time.
If the message has the correct sent time, the call to MSMQQueue.ReceiveCurrent removes the message and Message Queuing moves the cursor to the next message.
If the message does not have the correct sent time, the call to MSMQQueue.PeekNext moves the cursor to the next message.
When there are no messages left, call MSMQQueue.Close to release resources used to open queue and exit the Sub procedure.
The following code example can be run on all versions of Message Queuing.
Private Sub FilterSentTime( _ strQueueName As String, _ strComputerName As String, _ dSentTime As Date _ ) ' Declare Message Queuing objects. Dim qinfo As New MSMQQueueInfo Dim q As MSMQQueue Dim msg As MSMQMessage ' Set the path name in the MSMQQueueInfo object. qinfo.PathName = strComputerName & "\" & strQueueName ' Open the public queue with receive access. On Error GoTo ErrorHandler Set q = qinfo.Open(Access:=MQ_RECEIVE_ACCESS, ShareMode:=MQ_DENY_NONE) ' Initialize the cursor. Set msg = q.PeekCurrent(ReceiveTimeout:=1000) ' Peek at the messages in the queue. Do While Not msg Is Nothing ' Check if the message was sent at the requested time. If msg.SentTime = dSentTime Then ' Remove the message. Set msg = q.ReceiveCurrent(ReceiveTimeout:=1000) MsgBox "A message with the requested sending time was removed." Set msg = q.PeekCurrent(ReceiveTimeout:=1000) Else Set msg = q.PeekNext(ReceiveTimeout:=1000) End If Loop ' Close the queue. q.Close Exit Sub ErrorHandler: MsgBox "Error " + Hex(Err.Number) + " was returned. " + Chr(13) + _ "Description: " + Err.Description If Not q Is Nothing And q.IsOpen2 Then q.Close EndIf End Sub