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vb.net Threading QuestionI have a thread that does periodic database maintenance. While this
process is going on I would like the rest of the application to hold off on accessing the database. I thought I could share a property in a class to hold the status, but that doesn't seem to work. Any ideas on what the best way for me to determine when the thread is doing it's work? Thanks Mike Mike,
>I have a thread that does periodic database maintenance. While this Don't use a thread, wait until the process is done.> process is going on I would like the rest of the application to hold > off on accessing the database. I thought I could share a property in a > class to hold the status, but that doesn't seem to work. > > Any ideas on what the best way for me to determine when the thread is > doing it's work? > (You can show a nice wait cursor on your screen) Cor Thanks, but in this case the thread is required.
Mike
> Thanks, but in this case the thread is required. What are than the things the users should be able to keep on doing while he cannot get information? To give us an impression. Cor Here is one scenerio.
A thread continually checks the Sql Server to make sure it is available and is responsive. This is done so that another part of the app can gather information and post it to the Sql Server without waiting for connection time out's etc. The information gathering has to work without interuption. If the Server is not responsive, then the information gathering saves the information to a local workstation and will try later to post. So, if the thread is checking the pulse of the Sql Server, how do I let the main part of the app know that the pulse is good? Mike,
Probably would I set the checks in a Thread with just a global switch that tells that the server is available or not. In principle does only that thread change this switch. (However, see the rest) The only part that the mainthread does than looking at this switch to decide to save or to update it. When you start your maintenance you can use another switch that prevents this process to change the first switch and set this first switch (therefore it has on both places to be synclocked). While the maintenance switch is busy the first switch is not updated by the checking thread (it even can be aborted). Probably I would use two switches to stop the checking thread as well. If I wrote something wrong it is more the idea. Just my thought, Cor <mmitch***@capstonetechnology.com> schrieb
> I have a thread that does periodic database maintenance. While this The simplest thing is probably using Synclock on the Connection object.> process is going on I would like the rest of the application to hold > off on accessing the database. I thought I could share a property in > a class to hold the status, but that doesn't seem to work. > > Any ideas on what the best way for me to determine when the thread > is doing it's work? Armin I think I have found my answer in on-line help..
Returning values from procedures that run on separate threads is complicated by the fact that the procedures cannot be functions and cannot use ByRef arguments. The best way to return values is to have your multithreaded procedure call a procedure in your application, and then pass the results as arguments. To do this, raise an event when a task is done, and process the results with an event handler. The following example returns a value by raising an event from a procedure running on a separate thread: <mmitch***@capstonetechnology.com> schrieb
> I think I have found my answer in on-line help.. I thought it was a synchronization problem, not a > > Returning values from procedures that run on separate threads is > complicated by the fact that the procedures cannot be functions and > cannot use ByRef arguments. The best way to return values is to have > your multithreaded procedure call a procedure in your application, > and then pass the results as arguments. To do this, raise an event > when a task is done, and process the results with an event handler. > > The following example returns a value by raising an event from a > procedure running on a separate thread: > how-to-return-results-from-a-thread problem. Armin |
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