Update one form from another

[JohnSouth]

Hi

In a c# Windows Forms application (not asp.net) if I've opened 2 or
more non-modal forms using code like:

FormTypeA aForm = new FormTypeA();
aForm .Show();

FormTypeB bForm = new FormTypeB();
bForm .Show();


How do I update a control (e.g. label) in aForm from code in bForm?
And will the update be seen immediately, or on activation?

John South

https://www.wherecanwego.com

Pangbourne UK

[bob]

Re: Update one form from another

Hi John,
Suggest you use events to communicate between forms.

If formA instantiates FormB then
Declare a custom event (say MySpecialEvent) in FormB with the payload that
you want to deliver.

Declare your FormB variable at FormA Class Level and write a
FormB.MySpecial Event Eventhandler.

The update will occur when events are handled. Depending on where you are in
your code you may have to issue a DoEvents to get a timely update.
If both FormA and FormB are instantiated in FormC then you can still use the
same technique by FormC responding to FormA and then raising an Interrrupt
which is responded to by FormB
Have a look at

http://www.codeproject.com/csharp/eventarguments.asp

HTH.
Bob
"JohnSouth" <JohnSouth104@g mail.com> wrote in message
news:1140284923 .935241.194280@ g14g2000cwa.goo glegroups.com.. .[color=blue]
> Hi
>
> In a c# Windows Forms application (not asp.net) if I've opened 2 or
> more non-modal forms using code like:
>
> FormTypeA aForm = new FormTypeA();
> aForm .Show();
>
> FormTypeB bForm = new FormTypeB();
> bForm .Show();
>
>
> How do I update a control (e.g. label) in aForm from code in bForm?
> And will the update be seen immediately, or on activation?
>
> John South
> www.wherecanwego.com
> Pangbourne UK
>[/color]

[stevehayter@ntlworld.com]

Re: Update one form from another

I'll second bob - events are the most elegant way here.

I shouldn't be posting this, but there is a 'hacky' way to do it
(particularly if you're not familiar with events in .NET). Remember,
Forms are objects - so just add a get accessor, (or a method if you
need to do a whole lotta stuff) to the FormTypeA class, and construct
your bForm passing aForm as a parameter. You can update it before it is
shown, or whenever you like then.

FormTypeA aForm = new FormTypeA();
aForm .Show();

FormTypeB bForm = new FormTypeB(aForm );
// Constructor: public FormTypeB(FormT ypeA form)

string newvalue = "test";

bForm.MyAFormOb jectProperty.Ch angeLabel(newva lue); // Updates the value
bForm .Show();

However, this is poor programming practice and I strongly suggest
events! Once you understand them, they're unbelieveably cool and make
programming far more flexible :)

bob wrote:
[color=blue]
> Hi John,
> Suggest you use events to communicate between forms.
>
> If formA instantiates FormB then
> Declare a custom event (say MySpecialEvent) in FormB with the payload that
> you want to deliver.
>
> Declare your FormB variable at FormA Class Level and write a
> FormB.MySpecial Event Eventhandler.
>
> The update will occur when events are handled. Depending on where you are in
> your code you may have to issue a DoEvents to get a timely update.
> If both FormA and FormB are instantiated in FormC then you can still use the
> same technique by FormC responding to FormA and then raising an Interrrupt
> which is responded to by FormB
> Have a look at
> http://www.codeproject.com/csharp/eventarguments.asp
> HTH.
> Bob
> "JohnSouth" <JohnSouth104@g mail.com> wrote in message
> news:1140284923 .935241.194280@ g14g2000cwa.goo glegroups.com.. .[color=green]
> > Hi
> >
> > In a c# Windows Forms application (not asp.net) if I've opened 2 or
> > more non-modal forms using code like:
> >
> > FormTypeA aForm = new FormTypeA();
> > aForm .Show();
> >
> > FormTypeB bForm = new FormTypeB();
> > bForm .Show();
> >
> >
> > How do I update a control (e.g. label) in aForm from code in bForm?
> > And will the update be seen immediately, or on activation?
> >
> > John South
> > www.wherecanwego.com
> > Pangbourne UK
> >[/color][/color]

[Stephany Young]

Re: Update one form from another

What's 'hacky' about that and why is it 'poor programming practice'?


<stevehayter@nt lworld.com> wrote in message
news:1140292615 .095592.20160@g 14g2000cwa.goog legroups.com...[color=blue]
> I'll second bob - events are the most elegant way here.
>
> I shouldn't be posting this, but there is a 'hacky' way to do it
> (particularly if you're not familiar with events in .NET). Remember,
> Forms are objects - so just add a get accessor, (or a method if you
> need to do a whole lotta stuff) to the FormTypeA class, and construct
> your bForm passing aForm as a parameter. You can update it before it is
> shown, or whenever you like then.
>
> FormTypeA aForm = new FormTypeA();
> aForm .Show();
>
> FormTypeB bForm = new FormTypeB(aForm );
> // Constructor: public FormTypeB(FormT ypeA form)
>
> string newvalue = "test";
>
> bForm.MyAFormOb jectProperty.Ch angeLabel(newva lue); // Updates the value
> bForm .Show();
>
> However, this is poor programming practice and I strongly suggest
> events! Once you understand them, they're unbelieveably cool and make
> programming far more flexible :)
>
> bob wrote:
>[color=green]
>> Hi John,
>> Suggest you use events to communicate between forms.
>>
>> If formA instantiates FormB then
>> Declare a custom event (say MySpecialEvent) in FormB with the payload
>> that
>> you want to deliver.
>>
>> Declare your FormB variable at FormA Class Level and write a
>> FormB.MySpecial Event Eventhandler.
>>
>> The update will occur when events are handled. Depending on where you are
>> in
>> your code you may have to issue a DoEvents to get a timely update.
>> If both FormA and FormB are instantiated in FormC then you can still use
>> the
>> same technique by FormC responding to FormA and then raising an
>> Interrrupt
>> which is responded to by FormB
>> Have a look at
>> http://www.codeproject.com/csharp/eventarguments.asp
>> HTH.
>> Bob
>> "JohnSouth" <JohnSouth104@g mail.com> wrote in message
>> news:1140284923 .935241.194280@ g14g2000cwa.goo glegroups.com.. .[color=darkred]
>> > Hi
>> >
>> > In a c# Windows Forms application (not asp.net) if I've opened 2 or
>> > more non-modal forms using code like:
>> >
>> > FormTypeA aForm = new FormTypeA();
>> > aForm .Show();
>> >
>> > FormTypeB bForm = new FormTypeB();
>> > bForm .Show();
>> >
>> >
>> > How do I update a control (e.g. label) in aForm from code in bForm?
>> > And will the update be seen immediately, or on activation?
>> >
>> > John South
>> > www.wherecanwego.com
>> > Pangbourne UK
>> >[/color][/color]
>[/color]

[Peter Bromberg [C# MVP]]

Re: Update one form from another

Stephany,
Beats me! Certainly events are more flexible, but if it "ain't broke", then
don't fix it!
Peter

--
Co-founder, Eggheadcafe.com developer portal:

http://www.eggheadcafe.com

UnBlog:

http://petesbloggerama.blogspot.com

"Stephany Young" wrote:
[color=blue]
> What's 'hacky' about that and why is it 'poor programming practice'?
>
>
> <stevehayter@nt lworld.com> wrote in message
> news:1140292615 .095592.20160@g 14g2000cwa.goog legroups.com...[color=green]
> > I'll second bob - events are the most elegant way here.
> >
> > I shouldn't be posting this, but there is a 'hacky' way to do it
> > (particularly if you're not familiar with events in .NET). Remember,
> > Forms are objects - so just add a get accessor, (or a method if you
> > need to do a whole lotta stuff) to the FormTypeA class, and construct
> > your bForm passing aForm as a parameter. You can update it before it is
> > shown, or whenever you like then.
> >
> > FormTypeA aForm = new FormTypeA();
> > aForm .Show();
> >
> > FormTypeB bForm = new FormTypeB(aForm );
> > // Constructor: public FormTypeB(FormT ypeA form)
> >
> > string newvalue = "test";
> >
> > bForm.MyAFormOb jectProperty.Ch angeLabel(newva lue); // Updates the value
> > bForm .Show();
> >
> > However, this is poor programming practice and I strongly suggest
> > events! Once you understand them, they're unbelieveably cool and make
> > programming far more flexible :)
> >
> > bob wrote:
> >[color=darkred]
> >> Hi John,
> >> Suggest you use events to communicate between forms.
> >>
> >> If formA instantiates FormB then
> >> Declare a custom event (say MySpecialEvent) in FormB with the payload
> >> that
> >> you want to deliver.
> >>
> >> Declare your FormB variable at FormA Class Level and write a
> >> FormB.MySpecial Event Eventhandler.
> >>
> >> The update will occur when events are handled. Depending on where you are
> >> in
> >> your code you may have to issue a DoEvents to get a timely update.
> >> If both FormA and FormB are instantiated in FormC then you can still use
> >> the
> >> same technique by FormC responding to FormA and then raising an
> >> Interrrupt
> >> which is responded to by FormB
> >> Have a look at
> >> http://www.codeproject.com/csharp/eventarguments.asp
> >> HTH.
> >> Bob
> >> "JohnSouth" <JohnSouth104@g mail.com> wrote in message
> >> news:1140284923 .935241.194280@ g14g2000cwa.goo glegroups.com.. .
> >> > Hi
> >> >
> >> > In a c# Windows Forms application (not asp.net) if I've opened 2 or
> >> > more non-modal forms using code like:
> >> >
> >> > FormTypeA aForm = new FormTypeA();
> >> > aForm .Show();
> >> >
> >> > FormTypeB bForm = new FormTypeB();
> >> > bForm .Show();
> >> >
> >> >
> >> > How do I update a control (e.g. label) in aForm from code in bForm?
> >> > And will the update be seen immediately, or on activation?
> >> >
> >> > John South
> >> > www.wherecanwego.com
> >> > Pangbourne UK
> >> >[/color]
> >[/color]
>
>
>[/color]