|
web
newsgroups
|
|||||||||||||||||||||||
|
|||||||||||||||||||||||
MessageBox in Validating event cancels subsequent eventsIt appears displaying a messagebox in a validating event will cancel the subsequent event. In the program below, button 2's click event doesn't fire if you open a dialog box in button 1's validating event. Am I doing something wrong here? Thanks Al Imports system Imports system.windows.forms ' Create a form, add two buttons and event handlers. ' Click on Button 2 to receive Button 1 validating ' event but not button 2's click event. MessageBox ' appears to kill the click event. Module ValidateTest Sub Main() Dim frm As New Form() Dim btn As New Button btn.Text = "One" btn.Parent = frm AddHandler btn.Validating, AddressOf BtnValidating btn = New Button btn.Left = btn.Width + 3 btn.Text = "Two" btn.Parent = frm AddHandler btn.Click, AddressOf BtnClick Application.Run(frm) End Sub Private Sub BtnValidating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) MessageBox.Show("BtnValidating event") End Sub Private Sub BtnClick(ByVal sender As Object, ByVal e As System.EventArgs) MessageBox.Show("BtnClick event") End Sub End Module Al Santino wrote:
> It appears displaying a messagebox in a validating event will cancel the I'm not sure I understand the problem. Why would the second button's> subsequent event. In the program below, button 2's click event doesn't fire > if you open a dialog box in button 1's validating event. Am I doing > something wrong here? click event be fired when the Validating event for button 1 fires? Show quoteHide quote > > <code snipped> >
Show quote
Hide quote
"Chris Dunaway" <dunaw***@gmail.com> wrote in message Well, I thought it would fire because that was how it's supposed to work.news:1155145580.240502.110380@n13g2000cwa.googlegroups.com... > Al Santino wrote: >> It appears displaying a messagebox in a validating event will cancel the >> subsequent event. In the program below, button 2's click event doesn't >> fire >> if you open a dialog box in button 1's validating event. Am I doing >> something wrong here? > > I'm not sure I understand the problem. Why would the second button's > click event be fired when the Validating event for button 1 fires? > >> >> <code snipped> >> > If you remove the MessageBox call in the validation handler the click event fires for button 2. My understanding is that the second button's event should fire unless you set the cancel arg to true in the validation event handler.
Show quote
Hide quote
"Chris Dunaway" <dunaw***@gmail.com> wrote in message Actually I'm not suggesting it should fire WHEN the validating event fires news:1155145580.240502.110380@n13g2000cwa.googlegroups.com... > Al Santino wrote: >> It appears displaying a messagebox in a validating event will cancel the >> subsequent event. In the program below, button 2's click event doesn't >> fire >> if you open a dialog box in button 1's validating event. Am I doing >> something wrong here? > > I'm not sure I understand the problem. Why would the second button's > click event be fired when the Validating event for button 1 fires? > >> >> <code snipped> >> > but AFTER it fires since the validating event didn't set the cancel argument to true. Al Santino wrote:
> Actually I'm not suggesting it should fire WHEN the validating event fires Perhaps I misunderstood. Are you saying that after the validating> but AFTER it fires since the validating event didn't set the cancel argument > to true. event fires, then the click event for the button doesn't fire, even if you click the button? "Chris Dunaway" <dunaw***@gmail.com> wrote in message Yes. If you run the program, button 1 will start with the focus. If you news:1155159383.843891.118430@n13g2000cwa.googlegroups.com... > Al Santino wrote: > >> Actually I'm not suggesting it should fire WHEN the validating event >> fires >> but AFTER it fires since the validating event didn't set the cancel >> argument >> to true. > > Perhaps I misunderstood. Are you saying that after the validating > event fires, then the click event for the button doesn't fire, even if > you click the button? > click on button 2, the button 1 validating event will fire and the program will display the messagebox. After you close the message box, button 2 will get the focus but its click event will not fire. "Chris Dunaway" <dunaw***@gmail.com> wrote in message Or better put:news:1155159383.843891.118430@n13g2000cwa.googlegroups.com... > Al Santino wrote: > >> Actually I'm not suggesting it should fire WHEN the validating event >> fires >> but AFTER it fires since the validating event didn't set the cancel >> argument >> to true. > > Perhaps I misunderstood. Are you saying that after the validating > event fires, then the click event for the button doesn't fire, even if > you click the button? > Yes. If you run the program, button 1 will start with the focus. If you click on button 2, the button 1 validating event will fire and the program will display the messagebox. After you close the message box, button 2 will get the focus but its click event will not _have fired_. Al Santino wrote:
Show quoteHide quote > "Chris Dunaway" <dunaw***@gmail.com> wrote in message From the code posted I don't see why button2's click event would be > news:1155159383.843891.118430@n13g2000cwa.googlegroups.com... > >>Al Santino wrote: >> >> >>>Actually I'm not suggesting it should fire WHEN the validating event >>>fires >>>but AFTER it fires since the validating event didn't set the cancel >>>argument >>>to true. >> >>Perhaps I misunderstood. Are you saying that after the validating >>event fires, then the click event for the button doesn't fire, even if >>you click the button? >> > > Or better put: > > Yes. If you run the program, button 1 will start with the focus. If you > click on button 2, the button 1 validating event will fire and the program > will display the messagebox. After you close the message box, button 2 will > get the focus but its click event will not _have fired_. > > triggered at all. The click event will not fire simply because a button get's the focus. -- Rinze van Huizen C-Services Holland b.v Hello, Rinze,
Since the user HAS clicked on button2 with the mouse, I think this SHOULD be enough to cause its click event to fire. Sadly, it doesn't. Cheers, Randy C-Services Holland b.v. wrote: Show quoteHide quote > > From the code posted I don't see why button2's click event would be > triggered at all. The click event will not fire simply because a button > get's the focus. > R. MacDonald wrote:
> Now that I think about it, the button click event is not fired until> Since the user HAS clicked on button2 with the mouse, I think this > SHOULD be enough to cause its click event to fire. Sadly, it doesn't. > the button is *released*. Since the code is throwing up a message box, focus is away from Button2 therefore the click is not registered. Think about this: Suppose you had a textbox and a button on the form and you had the validating event on the textbox. Suppose you entered invalid data into the textbox and clicked the button, should the button click event still be fired if the textbox was not validated? I'm beginning to think this is by design, perhaps a bit unexpected, but by design. R. MacDonald wrote:
> Since the user HAS clicked on button2 with the mouse, I think this I'm not so sure. Look at this code below. If the textbox has the word> SHOULD be enough to cause its click event to fire. Sadly, it doesn't. hello in it when Button2 is clicked, should Button2's event fire anyway? I don't think so. I think the OP's problem is because of the Message Box. It steals focus from Button2 so that when the mouse is release, the message is not being sent to button 2. If you remove the Message Box from the validating event, the click event should fire. Public Class Form1 Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click MsgBox("Button 2 Clicked") End Sub Private Sub TextBox1_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating If TextBox1.Text.ToUpper = "HELLO" Then MsgBox("Invalid Value in textbox") e.Cancel = True End If End Sub End Class Yes, if you remove the Message Box things work fine. But I'd like to use
this in the case where someone enters fills in some controls on a form and then chooses to close the form. I want to give them a choice of canceling the quit, proceeding without saving, or proceeding and saving. This seems like a rather common behaviour. I would expect that setting the cancel arguement to "true" would cancel the subsequent click event and setting it to false would not. Show quoteHide quote "Chris Dunaway" <dunaw***@gmail.com> wrote in message news:1155324358.593558.177120@74g2000cwt.googlegroups.com... > R. MacDonald wrote: > >> Since the user HAS clicked on button2 with the mouse, I think this >> SHOULD be enough to cause its click event to fire. Sadly, it doesn't. > > I'm not so sure. Look at this code below. If the textbox has the word > hello in it when Button2 is clicked, should Button2's event fire > anyway? I don't think so. I think the OP's problem is because of the > Message Box. It steals focus from Button2 so that when the mouse is > release, the message is not being sent to button 2. If you remove the > Message Box from the validating event, the click event should fire. > > > > Public Class Form1 > > Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As > System.EventArgs) Handles Button2.Click > MsgBox("Button 2 Clicked") > End Sub > > Private Sub TextBox1_Validating(ByVal sender As System.Object, > ByVal e As System.ComponentModel.CancelEventArgs) Handles > TextBox1.Validating > If TextBox1.Text.ToUpper = "HELLO" Then > MsgBox("Invalid Value in textbox") > e.Cancel = True > End If > End Sub > End Class > Hello, Al,
Chris's idea that the event is being "absorbed" by the MessageBox may be on the right track, but I suspect this is not "by design" but is more likely due to lack of design. Either way, I can't see how to use this idea to come up with a work-around. But it sounds as if, rather than using the MessageBox as part of validating the contents of a control, you are actually using it to validate the closing of the form. I know it doesn't address the problem of the missing click event, but perhaps you can solve your problem by modifying your approach. In a similar case when I wanted the user to validate or cancel closing/saving, I have used the Form's Closing event for this purpose. (Well actually, since it was a base for several derived forms, I overrode the OnClosing method.) The main problem with this approach is that it is still necessary to invoke the Validation code for the currently ActiveControl. I haven't yet found a good generic way to do this (in VB), and so have had to add code to each derived form to find the active control and directly call its validation handler. (I think it should be possible to locate and call the handler in a generic fashion, and I'm still hoping to figure out how to do this.) Cheers, Randy Al Santino wrote: Show quoteHide quote > Yes, if you remove the Message Box things work fine. But I'd like to use > this in the case where someone enters fills in some controls on a form and > then chooses to close the form. I want to give them a choice of canceling > the quit, proceeding without saving, or proceeding and saving. This seems > like a rather common behaviour. > > I would expect that setting the cancel arguement to "true" would cancel the > subsequent click event and setting it to false would not. > > Hi Randy,
Would that it were. I have a SplitContainer with a list of items on the left and a form on the right. When you click on an item in the list on the left it displays the fields for the item on the right. You can edit the fields on the right. When you click on an item in the left the form's validate event fires to see whether you changed an item. If so, it displays a messagebox asking whether you wish to save your changes. I like your idea of using the form closing event but, unfortunately, the form doesn't close each time. I do appreciate your giving this some thought. Al Show quoteHide quote "R. MacDonald" <sci***@NO-SP-AMcips.ca> wrote in message news:44e0254a$0$7361$dbd41001@news.wanadoo.nl... > Hello, Al, > > Chris's idea that the event is being "absorbed" by the MessageBox may be > on the right track, but I suspect this is not "by design" but is more > likely due to lack of design. Either way, I can't see how to use this > idea to come up with a work-around. > > But it sounds as if, rather than using the MessageBox as part of > validating the contents of a control, you are actually using it to > validate the closing of the form. > > I know it doesn't address the problem of the missing click event, but > perhaps you can solve your problem by modifying your approach. > > In a similar case when I wanted the user to validate or cancel > closing/saving, I have used the Form's Closing event for this purpose. > (Well actually, since it was a base for several derived forms, I overrode > the OnClosing method.) The main problem with this approach is that it is > still necessary to invoke the Validation code for the currently > ActiveControl. I haven't yet found a good generic way to do this (in VB), > and so have had to add code to each derived form to find the active > control and directly call its validation handler. (I think it should be > possible to locate and call the handler in a generic fashion, and I'm > still hoping to figure out how to do this.) > > Cheers, > Randy > > > Al Santino wrote: >> Yes, if you remove the Message Box things work fine. But I'd like to use >> this in the case where someone enters fills in some controls on a form >> and then chooses to close the form. I want to give them a choice of >> canceling the quit, proceeding without saving, or proceeding and saving. >> This seems like a rather common behaviour. >> >> I would expect that setting the cancel arguement to "true" would cancel >> the subsequent click event and setting it to false would not. >> Hello, Al,
Yes, I can see that's a sticky problem. Too often in this sort of situation we end up succumbing to non-elegant work-arounds that involve "remembering" which control we were on, which control we were going to, whether or not we were navigating by mouse-click, tab or code, etc. and then programming around all the possibilities -- Very messy, because there are usually so many possibilities. I can't think of a good solution just now, but I'll let you know if I have any late-night inspirations. Cheers, Randy Al Santino wrote: Show quoteHide quote > Hi Randy, > > Would that it were. I have a SplitContainer with a list of items on the left > and a form on the right. When you click on an item in the list on the left > it displays the fields for the item on the right. You can edit the fields on > the right. When you click on an item in the left the form's validate event > fires to see whether you changed an item. If so, it displays a messagebox > asking whether you wish to save your changes. > > I like your idea of using the form closing event but, unfortunately, the > form doesn't close each time. I do appreciate your giving this some thought. > > Al > > > "R. MacDonald" <sci***@NO-SP-AMcips.ca> wrote in message > news:44e0254a$0$7361$dbd41001@news.wanadoo.nl... > >>Hello, Al, >> >>Chris's idea that the event is being "absorbed" by the MessageBox may be >>on the right track, but I suspect this is not "by design" but is more >>likely due to lack of design. Either way, I can't see how to use this >>idea to come up with a work-around. >> >>But it sounds as if, rather than using the MessageBox as part of >>validating the contents of a control, you are actually using it to >>validate the closing of the form. >> >>I know it doesn't address the problem of the missing click event, but >>perhaps you can solve your problem by modifying your approach. >> >>In a similar case when I wanted the user to validate or cancel >>closing/saving, I have used the Form's Closing event for this purpose. >>(Well actually, since it was a base for several derived forms, I overrode >>the OnClosing method.) The main problem with this approach is that it is >>still necessary to invoke the Validation code for the currently >>ActiveControl. I haven't yet found a good generic way to do this (in VB), >>and so have had to add code to each derived form to find the active >>control and directly call its validation handler. (I think it should be >>possible to locate and call the handler in a generic fashion, and I'm >>still hoping to figure out how to do this.) >> >>Cheers, >>Randy >> >> >>Al Santino wrote: >> >>>Yes, if you remove the Message Box things work fine. But I'd like to use >>>this in the case where someone enters fills in some controls on a form >>>and then chooses to close the form. I want to give them a choice of >>>canceling the quit, proceeding without saving, or proceeding and saving. >>>This seems like a rather common behaviour. >>> >>>I would expect that setting the cancel arguement to "true" would cancel >>>the subsequent click event and setting it to false would not. >>> > > Hello, Al,
I have tried your code (VB.Net 2003) and can confirm that I see the same (inappropriate) behaviour. It sure looks like a problem to me. I hope someone can provide an explanation and/or workaround. Cheers, Randy Al Santino wrote: Show quoteHide quote > Hi, > > It appears displaying a messagebox in a validating event will cancel the > subsequent event. In the program below, button 2's click event doesn't fire > if you open a dialog box in button 1's validating event. Am I doing > something wrong here? > Thanks > Al > > Imports system > Imports system.windows.forms > ' Create a form, add two buttons and event handlers. > ' Click on Button 2 to receive Button 1 validating > ' event but not button 2's click event. MessageBox > ' appears to kill the click event. > Module ValidateTest > Sub Main() > Dim frm As New Form() > Dim btn As New Button > btn.Text = "One" > btn.Parent = frm > AddHandler btn.Validating, AddressOf BtnValidating > > btn = New Button > btn.Left = btn.Width + 3 > btn.Text = "Two" > btn.Parent = frm > AddHandler btn.Click, AddressOf BtnClick > > Application.Run(frm) > End Sub > > Private Sub BtnValidating(ByVal sender As Object, > ByVal e As System.ComponentModel.CancelEventArgs) > MessageBox.Show("BtnValidating event") > End Sub > > Private Sub BtnClick(ByVal sender As Object, ByVal e As > System.EventArgs) > MessageBox.Show("BtnClick event") > End Sub > End Module > > > Hi Randy,
Thanks for taking the time to try it. I'll keep my fingers crossed about the workaround. Al Show quoteHide quote "R. MacDonald" <sci***@NO-SP-AMcips.ca> wrote in message news:44daed34$0$5469$dbd4b001@news.wanadoo.nl... > Hello, Al, > > I have tried your code (VB.Net 2003) and can confirm that I see the same > (inappropriate) behaviour. > > It sure looks like a problem to me. I hope someone can provide an > explanation and/or workaround. > > Cheers, > Randy > > > Al Santino wrote: >> Hi, >> >> It appears displaying a messagebox in a validating event will cancel the >> subsequent event. In the program below, button 2's click event doesn't >> fire if you open a dialog box in button 1's validating event. Am I doing >> something wrong here? >> Thanks >> Al >> >> Imports system >> Imports system.windows.forms >> ' Create a form, add two buttons and event handlers. >> ' Click on Button 2 to receive Button 1 validating >> ' event but not button 2's click event. MessageBox >> ' appears to kill the click event. >> Module ValidateTest >> Sub Main() >> Dim frm As New Form() >> Dim btn As New Button >> btn.Text = "One" >> btn.Parent = frm >> AddHandler btn.Validating, AddressOf BtnValidating >> >> btn = New Button >> btn.Left = btn.Width + 3 >> btn.Text = "Two" >> btn.Parent = frm >> AddHandler btn.Click, AddressOf BtnClick >> >> Application.Run(frm) >> End Sub >> >> Private Sub BtnValidating(ByVal sender As Object, >> ByVal e As System.ComponentModel.CancelEventArgs) >> MessageBox.Show("BtnValidating event") >> End Sub >> >> Private Sub BtnClick(ByVal sender As Object, ByVal e As >> System.EventArgs) >> MessageBox.Show("BtnClick event") >> End Sub >> End Module >> >> 
Other interesting topics
Referencing Controls created at run time.
MS VB Newbie Tutorial Dataset End all running code of .dll Class item not accessible because it's private... but it's not? Drawstring question... Description of Function How do I send null values to an integer type variable? Writing to a file opened in another class Launch External Program |
|||||||||||||||||||||||
