public static bool PollForMessage <T>(string queueName, Func <T, bool> action, int visibilityTimeoutSeconds = 30, Func <T, bool> condition = null) where T : AzureMessage
{
// Wrap condition in a wrapper function that converts the raw message into the type that condition wants
Func <CloudQueueMessage, bool> rawCondition = null;
if (condition != null)
{
rawCondition = rawMessage => condition.Invoke(AzureMessage.FromMessage(rawMessage) as T);
}
return(PollForMessageRawCondition <T>(queueName, action, visibilityTimeoutSeconds, rawCondition));
}
public static bool PollForMessageRawCondition <T>(string queueName, Func <T, bool> action, int visibilityTimeoutSeconds = 30, Func <CloudQueueMessage, bool> condition = null) where T : AzureMessage
{
CloudQueue queue = StorageAccount.CreateCloudQueueClient().GetQueueReference(queueName);
CloudQueueMessage queueMessage;
queue.CreateIfNotExist();
queueMessage = queue.GetMessage(new TimeSpan(0, 0, visibilityTimeoutSeconds));
if (queueMessage == null)
{
return(false);
}
T message = AzureMessage.FromMessage(queueMessage) as T;
if (condition != null && !condition.Invoke(queueMessage))
{
// Force the message to become visible on the queue, because we don't want to process it. See AzureHelperTest.AddThenDeleteMessageTest for a demonstration that this works.
queue.AddMessage(queueMessage);
queue.DeleteMessage(queueMessage);
return(false);
}
if (!action.Invoke(message))
{
return(false);
}
try
{
queue.DeleteMessage(queueMessage);
}
catch (StorageClientException e)
{
// It took too long to process the message and the visibility timeout expired
// See http://blog.smarx.com/posts/deleting-windows-azure-queue-messages-handling-exceptions
if (e.ExtendedErrorInformation.ErrorCode == "MessageNotFound")
{
System.Diagnostics.Trace.WriteLine("Visibility timeout expired: " + e);
return(false);
}
else
{
throw e;
}
}
return(true);
}