Databases
StackOverflow2013
Postsdbo
POProblems related to showing MessageBox from non-GUI threads
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POProblems related to showing MessageBox from non-GUI threads
    primarykey
    data
    text
    <p>I'm working on a heavily data-bound Win.Forms application where I've found some strange behavior. The app has separate I/O threads receiving updates through asynchronous web-requests which it then sends to the main/GUI thread for processing and updating of application-wide data-stores (which in turn may be data-bound to various GUI-elements, etc.). The server at the other end of the web-requests requires periodic requests or the session times out.</p> <p>I've gone through several attempted solutions of dealing with thread-issues etc. and I've observed the following behavior:</p> <ol> <li><p>If I use Control.Invoke for sending updates from I/O-thread(s) to main-thread and this update causes a MessageBox to be shown the main form's message pump stops until the user clicks the ok-button. This also blocks the I/O-thread from continuing eventually leading to timeouts on the server.</p></li> <li><p>If I use Control.BeginInvoke for sending updates from I/O-thread(s) to main-thread the main form's message pump does <em>not</em> stop, but if the processing of an update leads to a messagebox being shown, the processing of the rest of that update is halted until the user clicks ok. Since the I/O-threads keep running and the message pump keeps processing messages several BeginInvoke's for updates may be called before the one with the message box is finished. This leads to out-of-sequence updates which is unacceptable.</p></li> <li><p>I/O-threads add updates to a blocking queue (very similar to <a href="https://stackoverflow.com/questions/530211/creating-a-blocking-queuet-in-net/530228#530228">Creating a blocking Queue&lt;T&gt; in .NET?</a>). GUI-thread uses a Forms.Timer that periodically applies all updates in the blocking queue. This solution solves both the problem of blocking I/O threads and sequentiality of updates i.e. next update will be never be started until previous is finished. However, there is a small performance cost as well as introducing a latency in showing updates that is unacceptable in the long run. I would like update-processing in the main-thread to be event-driven rather than polling.</p></li> </ol> <p>So to my question. How should I do this to:</p> <ol> <li>avoid blocking the I/O-threads </li> <li>guarantee that updates are finished in-sequence</li> <li>keep the main message pump running while showing a message box as a result of an update.</li> </ol> <p>Update: See solution below</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCommunity
    1. USHans Løken
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POProblems related to showing MessageBox from non-GUI threads
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POProblems related to showing MessageBox from non-GUI threads
      1. USMatt Ellen
      1. VTFavorite
    3. VO
      singulars
      1. POProblems related to showing MessageBox from non-GUI threads
      1. USmafu
      1. VTFavorite
    1. COQuestion: Must the GUI only be updated after the user clicks OK on the messageBox or can they just be informed that an update has happened e.g. via a message in a MultiLine TextBox?
      singulars
      1. POProblems related to showing MessageBox from non-GUI threads
      1. USAsher
    2. COIt has to be a popup but I am uncertain if it needs to be modal. I could possibly create my own non-modal popup instead.
      singulars
      1. POProblems related to showing MessageBox from non-GUI threads
      1. USHans Løken
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload