I have a long process I run that needs to be complete before the user can continue. I can change the cursor to an hourglass, but I want to update the Status Strip on the bottom during the process. I set the statusstrip label to "Downloading... ", but it will not show up on the form. I need to display this message before it starts the process. I can put a thread.sleep for 1 second after I do the initial process, but that seems sloppy to me. Any suggestions? Here is my code launched from a button click:
'update the label--This does not show because the process starts before the UI updates
slDBList.Text = "Retrieving Databases..."Tr yMe.Cursor = Cursors.WaitCur sorDim lstServers As List(Of String)'set to false in case of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the servers list cbServers.DataS ource = Nothing'clear the databases list dbDatabases.Dat aSource = NothingIf chkSort.Checked = True ThenlstServers = GetSqlServers(T rue)ElselstServ ers = GetSqlServers(F alse)End IfcbServers.Dat aSource = lstServers'set to true to enabled the selected index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt = ""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error: " & ex.ToString, "Data Error", MessageBoxButto ns.OK, MessageBoxIcon. Error)boolServe rsLoaded = FalseslDBList.T ext = ""FinallyMe.Cur sor = Cursors.ArrowEn d Try
Jun 27 '08
32  1707 
When I do this I get a cross thread error. Any ideas?
John
"kimiraikko nen" <ki************ *@gmail.comwrot e in message
news:9a******** *************** ***********@r66 g2000hsg.google groups.com...
On May 21, 9:09 pm, "John Wright" <riley_wri...@h otmail.comwrote :
I have a long process I run that needs to be complete before the user can
continue. I can change the cursor to an hourglass, but I want to update
the Status Strip on the bottom during the process. I set the statusstrip
label to "Downloading... ", but it will not show up on the form. I need to
display this message before it starts the process. I can put a
thread.sleep for 1 second after I do the initial process, but that seems
sloppy to me. Any suggestions? Here is my code launched from a button
click:
'update the label--This does not show because the process starts before
the UI updates
slDBList.Text = "Retrieving Databases..."Tr yMe.Cursor =
Cursors.WaitCur sorDim lstServers As List(Of String)'set to false in case
of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the
servers list cbServers.DataS ource = Nothing'clear the databases list
dbDatabases.Dat aSource = NothingIf chkSort.Checked = True ThenlstServers =
GetSqlServers(T rue)ElselstServ ers = GetSqlServers(F alse)End
IfcbServers.Dat aSource = lstServers'set to true to enabled the selected
index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt =
""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error:
" & ex.ToString, "Data Error", MessageBoxButto ns.OK,
MessageBoxIcon. Error)boolServe rsLoaded = FalseslDBList.T ext =
""FinallyMe.Cur sor = Cursors.ArrowEn d Try
Hi,
Could you put the code above into BackgroundWorke r's Do_Work event sub
and run it using RunWorkerAsync method?
And just set statusStrip text in button_click event.
Like this:
Private Sub Button1_Click (ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
StatusStrip1.te xt = "Downloading... "
BackgroundWorke r1.RunWorketAsy nc()
End Sub
Private Sub BackgroundWorke r1_DoWork(ByVal sender As System.Object,
ByVal e As System.Componen tModel.DoWorkEv entArgs) Handles
Backgroundworke r1.DoWork
' Here is the code that you sent in your original post
End Sub
....should work fine.
Thanks,
Onur Güzel
Joergen,
Be aware that you never should do what you advice as it is a critical
process that has to be completed, and the user can end that in the middle
without knowing what is the effect.
Think by instance in a paying process by banks, were steps have to be done,
I would never be the one who would give an advice as yours.
Just my idea,
Cor
"Joergen Bech @ post1.tele.dk>" <jbech<NOSPAMNO SPAMschreef in bericht
news:7m******** *************** *********@4ax.c om...
>
Run the task on another thread. If you are using .Net 2.0 or later
(VS2005/VS2008), this is fairly easy with the BackgroundWorke r class.
http://msdn.microsoft.com/en-us/libr...undworker.aspx
Do not run the task on the UI thread or you will get the results you
are currently seeing.
/Joergen Bech
On Wed, 21 May 2008 12:09:09 -0600, "John Wright"
<ri**********@h otmail.comwrote :
>>I have a long process I run that needs to be complete before the user can
continue. I can change the cursor to an hourglass, but I want to update
the Status Strip on the bottom during the process. I set the statusstrip
label to "Downloading... ", but it will not show up on the form. I need to
display this message before it starts the process. I can put a
thread.slee p for 1 second after I do the initial process, but that seems
sloppy to me. Any suggestions? Here is my code launched from a button
click:
'update the label--This does not show because the process starts before
the UI updates
slDBList.Te xt = "Retrieving Databases..."Tr yMe.Cursor =
Cursors.WaitC ursorDim lstServers As List(Of String)'set to false in case
of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the
servers list cbServers.DataS ource = Nothing'clear the databases list
dbDatabases.D ataSource = NothingIf chkSort.Checked = True ThenlstServers =
GetSqlServers (True)ElselstSe rvers = GetSqlServers(F alse)End
IfcbServers.D ataSource = lstServers'set to true to enabled the selected
index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt =
""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error:
" & ex.ToString, "Data Error", MessageBoxButto ns.OK,
MessageBoxIco n.Error)boolSer versLoaded = FalseslDBList.T ext =
""FinallyMe.C ursor = Cursors.ArrowEn d Try
John,
Mostly it helps, when you set it in a seperate method.
Cor
"John Wright" <ri**********@h otmail.comschre ef in bericht news:eT******** ******@TK2MSFTN GP06.phx.gbl...
I have a long process I run that needs to be complete before the user can continue. I can change the cursor to an hourglass, but I want to update the Status Strip on the bottom during the process. I set the statusstrip label to "Downloading... ", but it will not show up on the form. I need to display this message before it starts the process. I can put a thread.sleep for 1 second after I do the initial process, but that seems sloppy to me. Any suggestions? Here is my code launched from a button click:
'update the label--This does not show because the process starts before the UI updates
slDBList.Text = "Retrieving Databases..."Tr yMe.Cursor = Cursors.WaitCur sorDim lstServers As List(Of String)'set to false in case of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the servers list cbServers.DataS ource = Nothing'clear the databases list dbDatabases.Dat aSource = NothingIf chkSort.Checked = True ThenlstServers = GetSqlServers(T rue)ElselstServ ers = GetSqlServers(F alse)End IfcbServers.Dat aSource = lstServers'set to true to enabled the selected index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt = ""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error: " & ex.ToString, "Data Error", MessageBoxButto ns.OK, MessageBoxIcon. Error)boolServe rsLoaded = FalseslDBList.T ext = ""FinallyMe.Cur sor = Cursors.ArrowEn d Try
Sorry,
I had not yet readed Mayurs answer,
That is most probably your answer,
As that does not work, combine his and mine.
Cor
"Cor Ligthert[MVP]" <no************ @planet.nlschre ef in bericht news:BF******** *************** ***********@mic rosoft.com...
John,
Mostly it helps, when you set it in a seperate method.
Cor
"John Wright" <ri**********@h otmail.comschre ef in bericht news:eT******** ******@TK2MSFTN GP06.phx.gbl...
I have a long process I run that needs to be complete before the user can continue. I can change the cursor to an hourglass, but I want to update the Status Strip on the bottom during the process. I set the statusstrip label to "Downloading... ", but it will not show up on the form. I need to display this message before it starts the process. I can put a thread.sleep for 1 second after I do the initial process, but that seems sloppy to me. Any suggestions? Here is my code launched from a button click:
'update the label--This does not show because the process starts before the UI updates
slDBList.Text = "Retrieving Databases..."Tr yMe.Cursor = Cursors.WaitCur sorDim lstServers As List(Of String)'set to false in case of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the servers list cbServers.DataS ource = Nothing'clear the databases list dbDatabases.Dat aSource = NothingIf chkSort.Checked = True ThenlstServers = GetSqlServers(T rue)ElselstServ ers = GetSqlServers(F alse)End IfcbServers.Dat aSource = lstServers'set to true to enabled the selected index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt = ""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error: " & ex.ToString, "Data Error", MessageBoxButto ns.OK, MessageBoxIcon. Error)boolServe rsLoaded = FalseslDBList.T ext = ""FinallyMe.Cur sor = Cursors.ArrowEn d Try
From what I understand, we were talking about a heavy, long-running
task with an unresponsive interface. In the case of a bank
transaction, we would be dealing with an optimistic or pessimistic
locking problem - not a threading one, as multithreading would be
entirely inappropriate in such a scenario.
The BackgroundWorke r class is there for a reason and I was not
the only one suggesting it.
The class provides properties, events, and methods for controlling
how an asynchronous task could or should be aborted.
It is up to the coder to use these properly to ensure that the ACID
properties of the operation are maintained.
The form that initiated the process should not just kill it directly
at the user's request: The pattern is to send a signal to the task,
asking it to cancel itself. The long-running task should periodically
check this flag and either ignore it or do whatever is necessary to
back out of whatever it is doing.
I have used BackgroundWorke r myself in a similar scenario and I
can assure you that I took steps to ensure that the only thing the
user could do was watch the progress or cancel the operation
before being able to do anything else.
As for DoEvents as an alternative, I would like to direct you and
the original poster to these articles: http://www.codinghorror.com/blog/archives/000159.html http://www.codinghorror.com/blog/archives/000370.html
Bear in mind that the first article before BackgroundWorke r came
onto the scene and made life much easier in this regard.
The important thing is the comments section, which contains
information and anecdotes that could be said to be of more
value than the articles themselves.
For my own part, I have seen applications where DoEvents
statements were littered all over the place to improve responsiveness.
Those apps were a mess of reentrancy problems, which only goes
to show that if you do not know what you are doing in the first place,
you should not touch DoEvents, let alone BackgroundWorke r.
Though DoEvents code is "easier" to debug than BackgroundWorke r
ditto, the issues are the same.
Better to have an unresponsive application that works than a
responsive one that doesn't.
Getting back to BackgroundWorke r: The code example in the
online documentation should be enough to getting started with.
Regards,
Joergen Bech
On Thu, 22 May 2008 05:45:30 +0200, "Cor Ligthert[MVP]"
<no************ @planet.nlwrote :
>Joergen,
Be aware that you never should do what you advice as it is a critical
process that has to be completed, and the user can end that in the middle
without knowing what is the effect.
Think by instance in a paying process by banks, were steps have to be done,
I would never be the one who would give an advice as yours.
Just my idea,
Cor
"Joergen Bech @ post1.tele.dk>" <jbech<NOSPAMNO SPAMschreef in bericht
news:7m******* *************** **********@4ax. com...
>>
Run the task on another thread. If you are using .Net 2.0 or later
(VS2005/VS2008), this is fairly easy with the BackgroundWorke r class.
http://msdn.microsoft.com/en-us/libr...undworker.aspx
Do not run the task on the UI thread or you will get the results you
are currently seeing.
/Joergen Bech
On Wed, 21 May 2008 12:09:09 -0600, "John Wright"
<ri**********@ hotmail.comwrot e:
>>>I have a long process I run that needs to be complete before the user can
continue. I can change the cursor to an hourglass, but I want to update
the Status Strip on the bottom during the process. I set the statusstrip
label to "Downloading... ", but it will not show up on the form. I need to
display this message before it starts the process. I can put a
thread.sle ep for 1 second after I do the initial process, but that seems
sloppy to me. Any suggestions? Here is my code launched from a button
click:
'update the label--This does not show because the process starts before
the UI updates
slDBList.Tex t = "Retrieving Databases..."Tr yMe.Cursor =
Cursors.Wait CursorDim lstServers As List(Of String)'set to false in case
of an error boolServersLoad ed = FalseboolDBLoad ed = False'clear the
servers list cbServers.DataS ource = Nothing'clear the databases list
dbDatabases. DataSource = NothingIf chkSort.Checked = True ThenlstServers =
GetSqlServer s(True)ElselstS ervers = GetSqlServers(F alse)End
IfcbServers. DataSource = lstServers'set to true to enabled the selected
index change on the dropdown boolServersLoad ed = TrueslDBList.Te xt =
""Catch ex As ExceptionMessag eBox.Show("Erro r loading server list. Error:
" & ex.ToString, "Data Error", MessageBoxButto ns.OK,
MessageBoxIc on.Error)boolSe rversLoaded = FalseslDBList.T ext =
""FinallyMe. Cursor = Cursors.ArrowEn d Try
"Mayur H Chauhan" <ma***@orioninc .comschrieb
How about Application.DoE vents ? This might help for processing
pending thread.
Doevents should not be used anymore. It was valid with previous VB
versions where multi threading was (appart from appartment threading)
almost impossible. Doevents creates more problems than necessary. First,
the classification of UI tasks and independent other tasks would have to
be removed. Not every task has an abstract and regular event/callback
mechanism that can be used to update the UI, especially when talking
about long running database activities. In addition, you'd have
to be aware of code reentrance. Moreover, why create new code to process
messages even if there is already a message loop that is made for it? My
experience is that almost every time when I was using Doevents, 5 LOC
later I'd wished to go the "clean" way and had used a separate thread
instead.
Armin
"Cor Ligthert[MVP]" <no************ @planet.nlschri eb
Joergen,
Be aware that you never should do what you advice as it is a
critical process that has to be completed, and the user can end that
in the middle without knowing what is the effect.
Think by instance in a paying process by banks, were steps have to
be done, I would never be the one who would give an advice as yours.
Just my idea,
Cor
Like Joergen, I don't understand this plea. Using another thread to
avoid the UI thread being blocked is the (only) right action, IMO. But
maybe you meant that the UI thread also have to be in an appropriate
state depending on the whole situation, where I would agree.
Armin
On Thu, 22 May 2008 11:09:12 +0200, "Armin Zingler"
<az*******@free net.dewrote:
>"Mayur H Chauhan" <ma***@orioninc .comschrieb
>How about Application.DoE vents ? This might help for processing
pending thread.
Doevents should not be used anymore. It was valid with previous VB
versions where multi threading was (appart from appartment threading)
almost impossible. Doevents creates more problems than necessary. First,
the classification of UI tasks and independent other tasks would have to
be removed. Not every task has an abstract and regular event/callback
mechanism that can be used to update the UI, especially when talking
about long running database activities. In addition, you'd have
to be aware of code reentrance. Moreover, why create new code to process
messages even if there is already a message loop that is made for it? My
experience is that almost every time when I was using Doevents, 5 LOC
later I'd wished to go the "clean" way and had used a separate thread
instead.
Armin
I would like to add that as a general tool for UI responsiveness,
DoEvents is not all it is cracked up to be, as opposed to
BackgroundWorke r:
If we are just running a homogenous loop, sure, we can call DoEvents
every nn iterations, giving the interface a chance to refresh itself,
but if the long-running tasks consists of a number of different
subtasks, we cannot depend on all tasks to be able to call DoEvents
at the same, regular intervals. Suppose the task is waiting for a
response or timeout from a database server?
Using BackgroundWorke r (or threads), on the other hand, the
scenario is like this:
1. User initiates task.
2. UI displays "Processing ..."
3. User clicks Cancel button.
4. UI displays "Cancelling ..."
5. Message is sent to thread, asking it to stop whatever it is doing
6. When the task, which is dutifully monitoring the Cancel flag when
it can, has finished, it informs the thread about its status.
7. UI displays "Cancelled" or "Completed" .
So in the case of subtasks where it is not possible to call DoEvents
for a few seconds, the DoEvents approach would still result in a
- sometimes - unresponsive interface, whereas the BackgroundWorke r
approach would allow the user to click the Cancel button immediately
and then see a "Cancelling ..." message for a couple of seconds until
the task had a chance to respond.
Regards,
Joergen Bech
but if the long-running tasks consists of a number of different
subtasks, we cannot depend on all tasks to be able to call DoEvents
at the same, regular intervals.
Agree. That's what I meant with "Not every task has an abstract and
regular event/callback mechanism that can be used to update the UI,
especially when talking about long running database activities."
(But I see it as your agreement supplemented by the BGW)
Armin
On Thu, 22 May 2008 13:06:46 +0200, "Armin Zingler"
<az*******@free net.dewrote:
>but if the long-running tasks consists of a number of different
subtasks, we cannot depend on all tasks to be able to call DoEvents
at the same, regular intervals.
Agree. That's what I meant with "Not every task has an abstract and
regular event/callback mechanism that can be used to update the UI,
especially when talking about long running database activities."
So you did. And so much more nicely put than my long-winded
explanation. Do you know the type of person who reads half a
post, and, blinded to the details, thinks he has an idea what
the whole thing contains, proceeds to write a follow-up?
Well, that was a good example, however much I usually try to avoid
being such a person.
>(But I see it as your agreement supplemented by the BGW)
I'll pretend that additional information was my excuse for
posting it and saves some face.
Regards,
Joergen Bech This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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