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Form Visibility Issue VB.NET 2003I am having a problem with a windows form when controlling its visibility. My application has a form that displays a timing function. Normally the timing form is hidden. An object has a timer that causes some processing to happen and at certain times it is required to make the timing display visible. To do this it calls a delegate to request that the form be displayed. Up until this point the hidden form is being upated by the same delegate with time information, but it is hidden. When the show event happens the outline of the form appears and the application becomes non-responsive to any future requests to hide or display the form. This appears like a threading issue, but as I understand it as long as the timing form is being called from the timer thread through "Invoke", which it is, it should work. Any suggestions please. Thank you, Sid. "Sid Price" <s**@nowhere.com> wrote in You might want to try BeginInvoke instead.news:uCplUgYZGHA.3400@TK2MSFTNGP02.phx.gbl: > When the show event happens the outline of the form appears and the > application becomes non-responsive to any future requests to hide or > display the form. > > This appears like a threading issue, but as I understand it as long as > the timing form is being called from the timer thread through > "Invoke", which it is, it should work. Any suggestions please. So althought invoke is correct - if the invoked function takes a long time to run, it'll still block the UI. Also any sub calls? They should all be checked for InvokeRequired as well. Oh lastly - were all objects created on same thread? If not - you'll need to check Object.InvokeRequired on each object - so that the call is marhsalled to the right thread.
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"Spam Catcher" <spamhoneypot@rogers.com> wrote in message Many thanks for your note (whoever you are :o)) I implemented the news:Xns97ACB58D1BAACusenethoneypotrogers@127.0.0.1... > "Sid Price" <s**@nowhere.com> wrote in > news:uCplUgYZGHA.3400@TK2MSFTNGP02.phx.gbl: > >> When the show event happens the outline of the form appears and the >> application becomes non-responsive to any future requests to hide or >> display the form. >> >> This appears like a threading issue, but as I understand it as long as >> the timing form is being called from the timer thread through >> "Invoke", which it is, it should work. Any suggestions please. > > You might want to try BeginInvoke instead. > > So althought invoke is correct - if the invoked function takes a long time > to run, it'll still block the UI. > > Also any sub calls? They should all be checked for InvokeRequired as well. > > Oh lastly - were all objects created on same thread? If not - you'll need > to check Object.InvokeRequired on each object - so that the call is > marhsalled to the right thread. "InvokeRequired" check and followed it with the "BeginInvoke" and this seems to have resolved the problem. Again, many thanks,. Sid. I have a little more information on this issue if anyone has any ideas I
would much appreciate hearing them: The problem occurs under the following two conditions. 1. The dipslay form is hidden and needs to be shown, AND 2. The call to show the display form is NOT in the thread that instantiated the form. Note that the following code is used to figure out if the call needs to use BeginInvoke or not: If mDisplayWindow.InvokeRequired = True Then mDisplayWindow.BeginInvoke(New DVisible(AddressOf Delegate_Visible), New Object() {DisplayVisible}) Else mDisplayWindow.Visible = DisplayVisible End If I have checked that when the request to show the form comes from the thread BeginInvoke is being called regardless of the form being currently visible or not. Thank you, Sid. Show quoteHide quote "Spam Catcher" <spamhoneypot@rogers.com> wrote in message news:Xns97ACB58D1BAACusenethoneypotrogers@127.0.0.1... > "Sid Price" <s**@nowhere.com> wrote in > news:uCplUgYZGHA.3400@TK2MSFTNGP02.phx.gbl: > >> When the show event happens the outline of the form appears and the >> application becomes non-responsive to any future requests to hide or >> display the form. >> >> This appears like a threading issue, but as I understand it as long as >> the timing form is being called from the timer thread through >> "Invoke", which it is, it should work. Any suggestions please. > > You might want to try BeginInvoke instead. > > So althought invoke is correct - if the invoked function takes a long time > to run, it'll still block the UI. > > Also any sub calls? They should all be checked for InvokeRequired as well. > > Oh lastly - were all objects created on same thread? If not - you'll need > to check Object.InvokeRequired on each object - so that the call is > marhsalled to the right thread. 
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