Check if there are Messages in MessageQueue in C#?

Question

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Win2008-R2

Hello

I'm working with MessageQueue and I'd like to know if there a way to know if there are message on Queue or not. I'm using it, but is too slow:

C#

private bool HasMessage()
{
   return _MessageQueue.GetAllMessages().Count() > 0;
}

I'd appreciate if someone know a easy way to get this

Posted 5-Jun-13 9:02am

Jeankininho

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Sergey Alexandrovich Kryukov 5-Jun-13 15:27pm

Why? This is the whole point.
—SA

Jeankininho 5-Jun-13 15:35pm

My code is: while(HasMessage()); So while there are message in Queue...

Sergey Alexandrovich Kryukov 5-Jun-13 15:39pm

Wrong approach! This is not how threading is reasonably uses. This is called "spin wait" and is a big abuse.
Please see my answer. If you need more help, explain the detail of your architecture, starting from you goal.
—SA

Jeankininho 5-Jun-13 15:45pm

I just want know:
There are a way to know if there are Messages on the queue? Simple.

Sergey Alexandrovich Kryukov 5-Jun-13 15:56pm

No. You are trying to abuse the code design, and I'm just trying to help you to overcome it; everything else is up to you.
And thank you for accepting my answer, I really think it should help you.
—SA

2 solutions

Solution 1

Hello,

Have a look at this documentation on MSDN. I think this is what you are looking for.

Regards,

Posted 5-Jun-13 9:22am

Prasad Khandekar

Comments

Sergey Alexandrovich Kryukov 5-Jun-13 15:35pm

It won't answer the question, because this call is blocking.
However, the thing is: this is what OP should really be doing. In other words, the code design should be reviewed the way not using information of the queue item count.

I actually answered in detail, please see Solution 2.

—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2013-06-05T09:27:00

Such property is not available, due to the multithreading nature of the class System.Messaging.MessageQueue:
http://msdn.microsoft.com/en-us/library/system.messaging.messagequeue.aspx[^].

You can thing of it as of some full-proof feature. Otherwise, what does it mean if you check up availability of the message at some moment of time and assign the result to, say, some Boolean or integer ("count") variable/member? During this operation, the only available message could be removed by some other thread, or some message could be added to the previously empty queue. Even if the thread synchronization operation is used on the queue operations, it can happen during assignment operations or somewhere else.

You can get the equivalent effect if you simply peek a message (that is, get without removing from the queue) with some small timeout: http://msdn.microsoft.com/en-us/library/t5te2tk0.aspx[^].

But this is not a really correct approach. Instead, you should review your code design the way not using message count at all. The technique is designed to be used in separate thread, which perform blocking calls, and, in particular, are put to the wait state unconditionally, until a message becomes available. This is that very main blocking operation: http://msdn.microsoft.com/en-us/library/829zyck7.aspx[^].

—SA