C-C++ Code Example: Retrieving PROPID_Q_LABEL

 

Updated: July 19, 2016

Applies To: Windows 10, Windows 7, Windows 8, Windows 8.1, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server Technical Preview, Windows Vista

This example provides an application-defined function that retrieves the PROPID_Q_LABEL property of an existing queue and returns the label to the caller.

This function can return the label of a local private queue from information stored on the local computer, but must retrieve information stored in the directory service to return the label of a local or remote public queue. This function cannot be used to obtain the label of a remote private queue.

A direct format name can be passed to this function only for a local private queue.

To retrieve PROPID_Q_LABEL

  1. Define the maximum number of queue properties to be specified and the queue property counter.

  2. Define the MQQUEUEPROPS structure.

  3. Specify PROPID_Q_LABEL

  4. Initialize the MQQUEUEPROPS structure.

  5. Validate the input parameters provided by the caller.

  6. Call MQGetQueueProperties to retrieve the label of the queue. If the call fails the returned error code is returned to the caller.

  7. Pass a pointer to the string containing the retrieved label of the queue to the caller on return.

System_CAPS_ICON_note.jpg Note

After your application no longer needs the label buffer, the caller must free the memory allocated for it using MQFreeMemory.

The following code example can be run on all versions of Message Queuing.

HRESULT GetQueueLabelProp(  
                          LPCWSTR wszQueueFormatName,   
                          LPWSTR *pwszValue  
                          )  
{  
  
  // Define the maximum number of queue properties and a property counter.  
  const int NUMBEROFPROPERTIES = 1;  
  DWORD cPropId=0;  
  
  // Define a queue property structure.  
  MQQUEUEPROPS   QueueProps;  
  QUEUEPROPID    aQueuePropId[NUMBEROFPROPERTIES];  
  MQPROPVARIANT  aQueuePropVar[NUMBEROFPROPERTIES];  
  HRESULT        aQueuePropStatus[NUMBEROFPROPERTIES];  
  HRESULT hr = MQ_OK;  
  
  // Specify the PROPID_Q_LABEL property.  
  aQueuePropId[cPropId] = PROPID_Q_LABEL;       // Property ID  
  aQueuePropVar[cPropId].vt = VT_NULL;          // Type indicator  
  cPropId++;  
  
  // Initialize the MQQUEUEPROPS structure.  
  QueueProps.cProp = cPropId;  
  QueueProps.aPropID = aQueuePropId;  
  QueueProps.aPropVar = aQueuePropVar;  
  QueueProps.aStatus = aQueuePropStatus;  
  
  // Validate the input string.  
  if (wszQueueFormatName == NULL) return MQ_ERROR_INVALID_PARAMETER;  
  
  // Get the queue properties.  
  hr = MQGetQueueProperties(wszQueueFormatName, &QueueProps);  
  if (FAILED(hr))  
  {  
    return hr;  
  }  
  
  // Set *pwszValue to point to the string containing the queue label  
  // returned by MQGetQueueProperties.  
  *pwszValue = aQueuePropVar[0].pwszVal;  
  return hr;  
}  

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