 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
.NET Forum / .NET Framework / New Users / December 2004Updating a windows forms control from a thread
I've gotten this question a couple of times in interviews and I don't know what they are looking for: How do you update a control's property, such as a textbox.text property, from a thread, in .NET? It seems to me you just update it normally. What are the interviewers looking for here? Thanks. - W "DW" <dddddwwwww@hotmail.com> schrieb: > I've gotten this question a couple of times in interviews and I don't know > what they are looking for: > > How do you update a control's property, such as a textbox.text property, > from a thread, in .NET? It seems to me you just update it normally. What > are the interviewers looking for here? Always create your forms in your application's main UI thread. Instance members of Windows Forms forms and controls are not safe for multithreading, so accessing them directly can cause problems. In addition to that, your forms need a message pump which is normally provided by the app's main UI thread. More information: Multithreading in Windows Forms applications <URL:http://dotnet.mvps.org/dotnet/faqs/?id=multithreading&lang=en>  SignatureM S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://dotnet.mvps.org/dotnet/faqs/ Herfried, We have a problem based on updating the UI from worker threads.. Our app uses a docking style MDI UI, where each form is capable of receiving updates from a central "controller", as well as performing form specific tasks. We use the Control.Invoke() lark, which of course works, but when we are making updates to many forms (We could have a form showing a graph, one a table, one a report etc.. all based on their own interpretation fo the data being pumped out) we find that the UI becomes very slow, sticky and unmanageable. Is is possible to assign each form its own UI thread/message pump so they can all act independantly of each other? Steve > "DW" <dddddwwwww@hotmail.com> schrieb: >> I've gotten this question a couple of times in interviews and I don't [quoted text clipped - 15 lines] > Multithreading in Windows Forms applications > <URL:http://dotnet.mvps.org/dotnet/faqs/?id=multithreading&lang=en> Updating the GUI from a working thread is a big no-no... (thats just me quoting someone here) Picho > I've gotten this question a couple of times in interviews and I don't know > what they are looking for: [quoted text clipped - 4 lines] > > - W Thanks Picho. Then specifically, how would you do that? Could you provide a small code example. I've been looking for one unsuccessfully. Thanks again. - DW > Updating the GUI from a working thread is a big no-no... > [quoted text clipped - 10 lines] >> >> - W Well, I am no expert but... I have this good book by Chris Sells - " Windows Forms Programming in C#". there is a whole chapter discussing multi-threaded UI, and how shared data is to be accessed using monitors. personally (I might get banned from this group for my bad habbits...), I usually raise events from the worker thread that have handlers in the UI thread that reflects changes in the UI. an example can be provided if you provide a skeletal context of your specific problem. Picho. > Thanks Picho. Then specifically, how would you do that? Could you > provide a small code example. I've been looking for one unsuccessfully. [quoted text clipped - 15 lines] >>> >>> - W "DW" <dddddwwwww@hotmail.com> schrieb: > Thanks Picho. Then specifically, how would you do that? 'Control.Invoke'/'Control.BeginInvoke'. You'll find more information in my other reply. SignatureM S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://dotnet.mvps.org/dotnet/faqs/ Thank you to Herfried and Picho. Now I understand how to do this. - David > "DW" <dddddwwwww@hotmail.com> schrieb: >> Thanks Picho. Then specifically, how would you do that? > > 'Control.Invoke'/'Control.BeginInvoke'. You'll find more information in > my other reply. Herfried what do you say about my event drivven solution? > "DW" <dddddwwwww@hotmail.com> schrieb: >> Thanks Picho. Then specifically, how would you do that? > > 'Control.Invoke'/'Control.BeginInvoke'. You'll find more information in > my other reply. "Picho" <SPAM_picho@telhai.ac.il> schrieb: > Herfried what do you say about my event drivven solution? In general, event driven solutions are not thread-safe too, but this depends on the implementation of the event. More information: <URL:http://www.google.de/groups?selm=%23XkWlYOuCHA.1656%40TK2MSFTNGP09> SignatureM S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://dotnet.mvps.org/dotnet/faqs/ Theres no "in general" about it - it suggests there are situations where it is OK. Raising an event from the worker thread executes code on the worker thread that is part of the UI. YOU MUST NOT DO THIS. The mostr frustrating thing is that the WInforms classes don't tell you this ... until the next version, where in debug they will throw an exception. Regards Richard Blewett - DevelopMentor http://www.dotnetconsult.co.uk/weblog http://www.dotnetconsult.co.uk "Picho" <SPAM_picho@telhai.ac.il> schrieb: > Herfried what do you say about my event drivven solution? In general, event driven solutions are not thread-safe too, but this depends on the implementation of the event. More information: <URL:http://www.google.de/groups?selm=%23XkWlYOuCHA.1656%40TK2MSFTNGP09 To my understanding, the non-thread-safe operations are the += and -= of the event. what if I make sure these only happen before I start the worker thread and after it finishes working? > Theres no "in general" about it - it suggests there are situations where > it is OK. Raising an event from the worker thread executes code on the [quoted text clipped - 16 lines] > > <URL:http://www.google.de/groups?selm=%23XkWlYOuCHA.1656%40TK2MSFTNGP09
Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
|
Reply to this Message
|
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.