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    <p>From what I can tell, this behavior is <em>as intended</em> for <code>MessageQueue.CanWrite</code>. If you delve deep enough into the guts of the MessageQueue class, you'll find it creates some helper objects which influence the value of this property in the following manner:</p> <ol> <li><p>If you pass <code>QueueAccessMode.Send</code> (or <code>SendAndReceive</code>), an internal access mode helper will be created which returns <code>true</code> if <code>(this.accessMode &amp; QueueAccessMode.Send) != (QueueAccessMode)0</code>.</p></li> <li><p>If #1 is <code>true</code>, it then attempts to open the queue to store it into the cache, using the access mode and sharing you have requested. At this point a call to the native method <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/ms699817%28v=vs.85%29.aspx" rel="nofollow"><code>MQOpenQueue</code></a> is made, which has the following in its remarks (emphasis mine):</p> <blockquote> <p>If the access rights for opening the queue in the mode requested are not allowed for the calling application, the following two things can happen:</p> <ul> <li><strong>If <code>dwAccess</code> is set to <code>MQ_SEND_ACCESS</code>, <code>MQOpenQueue</code> will succeed</strong>, but errors will be returned when the application tries to send a message.</li> <li>If <code>dwAccess</code> is set to <code>MQ_PEEK_ACCESS</code> or <code>MQ_RECEIVE_ACCESS</code>, <code>MQOpenQueue</code> will fail and return <code>MQ_ERROR_ACCESS_DENIED</code> (0xC00E0025). In this case a queue handle is not returned to <code>phQueue</code>. </li> </ul> </blockquote></li> </ol> <p>Therefore, given a <code>QueueAccessMode.Send</code> (or <code>SendAndReceive</code>) with a valid queue name and sharing mode, it is my understanding that <code>CanWrite</code> will return <code>true</code>, even if you truly do not have access to send a message.</p> <p>Basically it appears that you will only receive <code>CanWrite == false</code> if and only if:</p> <ol> <li>You pass a <code>QueueAccessMode</code> which is not <code>Send</code> or <code>SendAndReceive</code>.</li> </ol>
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    1. POMessageQueue.CanWrite always returns true
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    1. COThanks for digging into this. Why would toggling the Receive Message permissions on the queue result in a true/false toggle of the "CanRead" property and when I send a message to the queue, with Send disabled, the message never makes it to the queue but I'm not receiving an exception either. That seems strange to me. I would think that CanRead and CanWrite would behave in the same manner.
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    2. CO@ChadLazette: I wish I had a better answer for you, but from what I can see this behavior is not based on the real permissions of the queue on the other end.
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    3. COFair enough. I appreciate it. I'll have to come up with another way to verify whether a user can send a message.
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