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Subclassed Textbox OnLeave OverridesI'm trying to make a subclass of the Textbox. One of the things I did there is the following: Protected Overrides Sub OnLeave(ByVal e As System.EventArgs) If Me.DataType = 1 Or Me.DataType = 2 Then If IsNumeric(Me.Text) Then Me.TextAlign = HorizontalAlignment.Right End If End If MyBase.OnLeave(e) End Sub For the sake of clarity I removed all the code that doesn't pertain to this problem. The offending code is the setting of the TextAlign property. This causes the focus to go back to the instance. In other words: When I try to tab to the next control on the form, the OnEnter event occurs again, and this control keeps the focus. When I take the setting of the TextAlign property out, the focus changes normally. Any ideas on how to prevent the focus shifting back when setting this property? Tia, Martin Try overriding OnLostFocus instead. That should work.
The reason this happens is because I think the control is recreated with a new handle when you do this... and I guess that throws a kink into "tab out" process. Changing the textalign property *after* the control has already lost focus should work. Show quoteHide quote "Martin" <x@y.com> wrote in message news:%23jcujkRKGHA.1848@TK2MSFTNGP12.phx.gbl... > Hi all, > > I'm trying to make a subclass of the Textbox. One of the things I did > there is the following: > > Protected Overrides Sub OnLeave(ByVal e As System.EventArgs) > If Me.DataType = 1 Or Me.DataType = 2 Then > If IsNumeric(Me.Text) Then > Me.TextAlign = HorizontalAlignment.Right > End If > End If > MyBase.OnLeave(e) > End Sub > > For the sake of clarity I removed all the code that doesn't pertain to > this problem. > The offending code is the setting of the TextAlign property. This causes > the focus to go back to the instance. In other words: When I try to tab to > the next control on the form, the OnEnter event occurs again, and this > control keeps the focus. When I take the setting of the TextAlign property > out, the focus changes normally. > > Any ideas on how to prevent the focus shifting back when setting this > property? > > Tia, > Martin > Hi CMM,
Thanks for your reply. Coming from VB6 I tried the onlostfocus first. But if I do it there, I get a Windows Exception (Could not create Handle or something). That is the reason why I moved the code here. Maybe I need an event that happens a bit earlier. Martin Show quoteHide quote "CMM" <cmm@nospam.com> wrote in message news:%23AO%236KSKGHA.1312@TK2MSFTNGP09.phx.gbl... > Try overriding OnLostFocus instead. That should work. > > The reason this happens is because I think the control is recreated with a > new handle when you do this... and I guess that throws a kink into "tab > out" process. Changing the textalign property *after* the control has > already lost focus should work. > > "Martin" <x@y.com> wrote in message > news:%23jcujkRKGHA.1848@TK2MSFTNGP12.phx.gbl... >> Hi all, >> >> I'm trying to make a subclass of the Textbox. One of the things I did >> there is the following: >> >> Protected Overrides Sub OnLeave(ByVal e As System.EventArgs) >> If Me.DataType = 1 Or Me.DataType = 2 Then >> If IsNumeric(Me.Text) Then >> Me.TextAlign = HorizontalAlignment.Right >> End If >> End If >> MyBase.OnLeave(e) >> End Sub >> >> For the sake of clarity I removed all the code that doesn't pertain to >> this problem. >> The offending code is the setting of the TextAlign property. This causes >> the focus to go back to the instance. In other words: When I try to tab >> to the next control on the form, the OnEnter event occurs again, and this >> control keeps the focus. When I take the setting of the TextAlign >> property out, the focus changes normally. >> >> Any ideas on how to prevent the focus shifting back when setting this >> property? >> >> Tia, >> Martin >> > > At what point does that exception get thrown? I don't get that error. Try
handling the LostFocus event instead of overriding OnLoadFocus. That works here. Hi CMM,
Followed your advice and used the lostfocus event itself. That worked! Thanks a lot! Being a newbie in .Net it still puzzles me somewhat... I read a few publications on overriding events, from SYBEX and from Microsoft itself. And they seem to contradict eachother. What I did is this (this worked): Private Sub Entrybox_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.LostFocus If Me.DataType = 1 Or Me.DataType = 2 Then If IsNumeric(Me.Text) Then Me.TextAlign = HorizontalAlignment.Right If Me.DataType = 2 Then Me.Text = Format(Val(Me.Text), "N") End If End If End If End Sub The thing I don't understand is the bit "Handles Me.LostFocus". According to a Microsoft publication this shouldn't be there, because it would trigger the LostFocus event twice. <QUOTE> Protected Overrides Sub Button1_Click(ByVal sender As System.Object, _ ByVal e as System.EventArgs) Static Counter as Integer = 0 Counter += 1 MessageBox.Show (" This inherited button has been clicked " & _ Counter.ToString() & " times.") End Sub The Handles clause is no longer associated with the method. This is not an oversight, but rather an important part of how events are handled in the ..NET Framework. The event handler is already associated with the event in the base class, and this association is passed on to the inheriting class. </QUOTE> However when I try to do the same with the "EntryBox_LostFocus" event, I get error messages from the IDE: "Sub 'EntryBox_LostFocus' cannot be declared 'overrides' because it does not override a sub in the base class. A perfectly understandable message, because the baseclass may know 'LostFocus' but definitely not 'EntryBox_LostFocus'. But without the "handles" clause how would 'EntryBox_LostFocus' get triggered? The Microsoft example doesn't seem to make a whole lot of sense. The Sybex book follows your recommendation, except that they use the 'Enter' and 'Leave' events. So, is the Microsoft example wrong? Or am I missing something? Martin Show quoteHide quote "CMM" <cmm@nospam.com> wrote in message news:Off8jhTKGHA.3936@TK2MSFTNGP12.phx.gbl... > At what point does that exception get thrown? I don't get that error. Try > handling the LostFocus event instead of overriding OnLoadFocus. That works > here. > The confusion I think lies in the difference between "Event LostFocus" and
"Sub OnLostFocus." OnLostFocus is the procedure in the base class that eventually ends up calling RaiseEvent LostFocus... consider it an Event Thrower. You can override this procedure and actually prevent the base class from throwing an event simply by neglecting to call "MyBase.OnLostFocus." Since OnLostFocus is not an "event" you don't do "Handles" on it... but rather you override it. More Info: In VB.Classic, if you were creating a class that threw events, it might be common for you to call RaiseEvent all over the place in your code (If SomeError Then RaiseEvent MyEvent). Although you can still do this in .NET, the "design practice" is to wrap up RaiseEvent in an overridable procedure. Then you would raise the event by calling the procedure (If SomeError Then OnMyEvent) rather than raising the event directly. This allows someone who wants to inherit from your class to override the event if they wanted to. Show quoteHide quote "Martin" <x@y.com> wrote in message news:uOBEXjXKGHA.3932@TK2MSFTNGP15.phx.gbl... > Hi CMM, > > Followed your advice and used the lostfocus event itself. That worked! > Thanks a lot! > > Being a newbie in .Net it still puzzles me somewhat... I read a few > publications on overriding events, from SYBEX and from Microsoft itself. > And they seem to contradict eachother. > > What I did is this (this worked): > > Private Sub Entrybox_LostFocus(ByVal sender As Object, ByVal e As > System.EventArgs) Handles Me.LostFocus > > If Me.DataType = 1 Or Me.DataType = 2 Then > If IsNumeric(Me.Text) Then > Me.TextAlign = HorizontalAlignment.Right > If Me.DataType = 2 Then > Me.Text = Format(Val(Me.Text), "N") > End If > End If > End If > > End Sub > > The thing I don't understand is the bit "Handles Me.LostFocus". According > to a Microsoft publication this shouldn't be there, because it would > trigger the LostFocus event twice. > > <QUOTE> > Protected Overrides Sub Button1_Click(ByVal sender As System.Object, _ > ByVal e as System.EventArgs) > Static Counter as Integer = 0 > Counter += 1 > MessageBox.Show (" This inherited button has been clicked " & _ > Counter.ToString() & " times.") > End Sub > > The Handles clause is no longer associated with the method. This is not an > oversight, but rather an important part of how events are handled in the > .NET Framework. The event handler is already associated with the event in > the base class, and this association is passed on to the inheriting class. > </QUOTE> > > However when I try to do the same with the "EntryBox_LostFocus" event, I > get error messages from the IDE: "Sub 'EntryBox_LostFocus' cannot be > declared 'overrides' because it does not override a sub in the base class. > > A perfectly understandable message, because the baseclass may know > 'LostFocus' but definitely not 'EntryBox_LostFocus'. But without the > "handles" clause how would 'EntryBox_LostFocus' get triggered? The > Microsoft example doesn't seem to make a whole lot of sense. > > The Sybex book follows your recommendation, except that they use the > 'Enter' and 'Leave' events. > > So, is the Microsoft example wrong? Or am I missing something? > > Martin > > > > "CMM" <cmm@nospam.com> wrote in message > news:Off8jhTKGHA.3936@TK2MSFTNGP12.phx.gbl... >> At what point does that exception get thrown? I don't get that error. Try >> handling the LostFocus event instead of overriding OnLoadFocus. That >> works here. >> > > Thanks a lot, I appreciate your help.
Show quoteHide quote "CMM" <cmm@nospam.com> wrote in message news:%23WHOg4aKGHA.2668@tk2msftngp13.phx.gbl... > The confusion I think lies in the difference between "Event LostFocus" and > "Sub OnLostFocus." OnLostFocus is the procedure in the base class that > eventually ends up calling RaiseEvent LostFocus... consider it an Event > Thrower. You can override this procedure and actually prevent the base > class from throwing an event simply by neglecting to call > "MyBase.OnLostFocus." > > Since OnLostFocus is not an "event" you don't do "Handles" on it... but > rather you override it. > > More Info: > In VB.Classic, if you were creating a class that threw events, it might be > common for you to call RaiseEvent all over the place in your code (If > SomeError Then RaiseEvent MyEvent). Although you can still do this in > .NET, the "design practice" is to wrap up RaiseEvent in an overridable > procedure. Then you would raise the event by calling the procedure (If > SomeError Then OnMyEvent) rather than raising the event directly. This > allows someone who wants to inherit from your class to override the event > if they wanted to. > > > "Martin" <x@y.com> wrote in message > news:uOBEXjXKGHA.3932@TK2MSFTNGP15.phx.gbl... >> Hi CMM, >> >> Followed your advice and used the lostfocus event itself. That worked! >> Thanks a lot! >> >> Being a newbie in .Net it still puzzles me somewhat... I read a few >> publications on overriding events, from SYBEX and from Microsoft itself. >> And they seem to contradict eachother. >> >> What I did is this (this worked): >> >> Private Sub Entrybox_LostFocus(ByVal sender As Object, ByVal e As >> System.EventArgs) Handles Me.LostFocus >> >> If Me.DataType = 1 Or Me.DataType = 2 Then >> If IsNumeric(Me.Text) Then >> Me.TextAlign = HorizontalAlignment.Right >> If Me.DataType = 2 Then >> Me.Text = Format(Val(Me.Text), "N") >> End If >> End If >> End If >> >> End Sub >> >> The thing I don't understand is the bit "Handles Me.LostFocus". According >> to a Microsoft publication this shouldn't be there, because it would >> trigger the LostFocus event twice. >> >> <QUOTE> >> Protected Overrides Sub Button1_Click(ByVal sender As System.Object, _ >> ByVal e as System.EventArgs) >> Static Counter as Integer = 0 >> Counter += 1 >> MessageBox.Show (" This inherited button has been clicked " & _ >> Counter.ToString() & " times.") >> End Sub >> >> The Handles clause is no longer associated with the method. This is not >> an oversight, but rather an important part of how events are handled in >> the .NET Framework. The event handler is already associated with the >> event in the base class, and this association is passed on to the >> inheriting class. >> </QUOTE> >> >> However when I try to do the same with the "EntryBox_LostFocus" event, I >> get error messages from the IDE: "Sub 'EntryBox_LostFocus' cannot be >> declared 'overrides' because it does not override a sub in the base >> class. >> >> A perfectly understandable message, because the baseclass may know >> 'LostFocus' but definitely not 'EntryBox_LostFocus'. But without the >> "handles" clause how would 'EntryBox_LostFocus' get triggered? The >> Microsoft example doesn't seem to make a whole lot of sense. >> >> The Sybex book follows your recommendation, except that they use the >> 'Enter' and 'Leave' events. >> >> So, is the Microsoft example wrong? Or am I missing something? >> >> Martin >> >> >> >> "CMM" <cmm@nospam.com> wrote in message >> news:Off8jhTKGHA.3936@TK2MSFTNGP12.phx.gbl... >>> At what point does that exception get thrown? I don't get that error. >>> Try handling the LostFocus event instead of overriding OnLoadFocus. That >>> works here. >>> >> >> > > By the way, I do also other stuff in the OnLeave event, such as:
If Me.DataType = 2 Then Me.Text = Format(Val(Me.Text), "N") End If And for some reason that does not give me any trouble. Don't TextAlign and Text use the same handle? Or does it have something to do with the fact that maybe one of the events is a Textbox event, and the other a Textboxbase event? Show quoteHide quote "CMM" <cmm@nospam.com> wrote in message news:%23AO%236KSKGHA.1312@TK2MSFTNGP09.phx.gbl... > Try overriding OnLostFocus instead. That should work. > > The reason this happens is because I think the control is recreated with a > new handle when you do this... and I guess that throws a kink into "tab > out" process. Changing the textalign property *after* the control has > already lost focus should work. > > "Martin" <x@y.com> wrote in message > news:%23jcujkRKGHA.1848@TK2MSFTNGP12.phx.gbl... >> Hi all, >> >> I'm trying to make a subclass of the Textbox. One of the things I did >> there is the following: >> >> Protected Overrides Sub OnLeave(ByVal e As System.EventArgs) >> If Me.DataType = 1 Or Me.DataType = 2 Then >> If IsNumeric(Me.Text) Then >> Me.TextAlign = HorizontalAlignment.Right >> End If >> End If >> MyBase.OnLeave(e) >> End Sub >> >> For the sake of clarity I removed all the code that doesn't pertain to >> this problem. >> The offending code is the setting of the TextAlign property. This causes >> the focus to go back to the instance. In other words: When I try to tab >> to the next control on the form, the OnEnter event occurs again, and this >> control keeps the focus. When I take the setting of the TextAlign >> property out, the focus changes normally. >> >> Any ideas on how to prevent the focus shifting back when setting this >> property? >> >> Tia, >> Martin >> > > By the way, you were right on the money with your suspicion that it had to
do with the handle. When I change the code like this: If Me.IsHandleCreated Then Me.TextAlign = HorizontalAlignment.Right End If I don't have a problem anymore. Of course the TextAlign doesn't work anymore either... Martin Show quoteHide quote "CMM" <cmm@nospam.com> wrote in message news:%23AO%236KSKGHA.1312@TK2MSFTNGP09.phx.gbl... > Try overriding OnLostFocus instead. That should work. > > The reason this happens is because I think the control is recreated with a > new handle when you do this... and I guess that throws a kink into "tab > out" process. Changing the textalign property *after* the control has > already lost focus should work. > > "Martin" <x@y.com> wrote in message > news:%23jcujkRKGHA.1848@TK2MSFTNGP12.phx.gbl... >> Hi all, >> >> I'm trying to make a subclass of the Textbox. One of the things I did >> there is the following: >> >> Protected Overrides Sub OnLeave(ByVal e As System.EventArgs) >> If Me.DataType = 1 Or Me.DataType = 2 Then >> If IsNumeric(Me.Text) Then >> Me.TextAlign = HorizontalAlignment.Right >> End If >> End If >> MyBase.OnLeave(e) >> End Sub >> >> For the sake of clarity I removed all the code that doesn't pertain to >> this problem. >> The offending code is the setting of the TextAlign property. This causes >> the focus to go back to the instance. In other words: When I try to tab >> to the next control on the form, the OnEnter event occurs again, and this >> control keeps the focus. When I take the setting of the TextAlign >> property out, the focus changes normally. >> >> Any ideas on how to prevent the focus shifting back when setting this >> property? >> >> Tia, >> Martin >> > > 
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