I have an application I'm working on where one form will open another.
This newly opened form needs to return a value based on the users actions.
My forms are not modal. I have seen discussions about overridding the
DialogResult, however I believe this will only work in a modal form
situation.
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to this
event and trap the value that was set if it wishes. The child form then
must be coded to raise this event when it is closing. This method works,
but I would prefer to use a more standard approach is there is one.
Does anyone have suggestions?
Thanks
Dan
7  2188 
On Mon, 01 Sep 2008 11:50:46 -0700, Dan Tallent <sp**@microsoft.comwrote:
[...]
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to
this
event and trap the value that was set if it wishes. The child form then
must be coded to raise this event when it is closing. This method
works,
but I would prefer to use a more standard approach is there is one.
If you just want the client form to retrieve the value when the child form
is closed, then I'd say the client form should just subscribe to the
FormClosed event. Then the child form should set some property that the
client form can retrieve when the FormClosed event is raised (the child
form would of course make sure this property is suitably set when it's
closed, before the FormClosed event is raised).
That said, other than the name of the event, what you've done is actually
a reasonably standard approach, depending on the semantics you want. The
..NET convention would be to have a property, and then an event with the
same name as the property, plus "Changed".
You could either only raise the "Changed" event when the form closes, or
you could allow for the client form to monitor changes as the user
provides input. Either way, that would be reasonable too.
Pete
Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the parent?
Thanks
Dan
"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
On Mon, 01 Sep 2008 11:50:46 -0700, Dan Tallent <sp**@microsoft.com>
wrote:
>[...]
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to
this
event and trap the value that was set if it wishes. The child form then
must be coded to raise this event when it is closing. This method
works,
but I would prefer to use a more standard approach is there is one.
If you just want the client form to retrieve the value when the child form
is closed, then I'd say the client form should just subscribe to the
FormClosed event. Then the child form should set some property that the
client form can retrieve when the FormClosed event is raised (the child
form would of course make sure this property is suitably set when it's
closed, before the FormClosed event is raised).
That said, other than the name of the event, what you've done is actually
a reasonably standard approach, depending on the semantics you want. The
.NET convention would be to have a property, and then an event with the
same name as the property, plus "Changed".
You could either only raise the "Changed" event when the form closes, or
you could allow for the client form to monitor changes as the user
provides input. Either way, that would be reasonable too.
Pete
Dan Tallent wrote:
Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the parent?
Thanks
Dan
"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
>On Mon, 01 Sep 2008 11:50:46 -0700, Dan Tallent <sp**@microsoft.com>
wrote:
>>[...]
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to
this
event and trap the value that was set if it wishes. The child form then
must be coded to raise this event when it is closing. This method
works,
but I would prefer to use a more standard approach is there is one.
If you just want the client form to retrieve the value when the child form
is closed, then I'd say the client form should just subscribe to the
FormClosed event. Then the child form should set some property that the
client form can retrieve when the FormClosed event is raised (the child
form would of course make sure this property is suitably set when it's
closed, before the FormClosed event is raised).
That said, other than the name of the event, what you've done is actually
a reasonably standard approach, depending on the semantics you want. The
.NET convention would be to have a property, and then an event with the
same name as the property, plus "Changed".
You could either only raise the "Changed" event when the form closes, or
you could allow for the client form to monitor changes as the user
provides input. Either way, that would be reasonable too.
Pete
You could use the FormClosing event.
Your client (or parent) form won't have released the instance, so the
instance count is not zero, and therefore it is not disposed. You won't
have an issue getting a property on the object from your instance.
"Dan Tallent" <sp**@microsoft.comwrote in message
news:e$**************@TK2MSFTNGP04.phx.gbl...
Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the
parent?
Thanks
Dan
"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
>On Mon, 01 Sep 2008 11:50:46 -0700, Dan Tallent <sp**@microsoft.com>
wrote:
>>[...]
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to
this
event and trap the value that was set if it wishes. The child form
then
must be coded to raise this event when it is closing. This method
works,
but I would prefer to use a more standard approach is there is one.
If you just want the client form to retrieve the value when the child
form is closed, then I'd say the client form should just subscribe to the
FormClosed event. Then the child form should set some property that the
client form can retrieve when the FormClosed event is raised (the child
form would of course make sure this property is suitably set when it's
closed, before the FormClosed event is raised).
That said, other than the name of the event, what you've done is actually
a reasonably standard approach, depending on the semantics you want. The
.NET convention would be to have a property, and then an event with the
same name as the property, plus "Changed".
You could either only raise the "Changed" event when the form closes, or
you could allow for the client form to monitor changes as the user
provides input. Either way, that would be reasonable too.
Pete
Sounds good.. now I have a plan.
Thanks
Dan
"Family Tree Mike" <Fa************@ThisOldHouse.comwrote in message
news:uw**************@TK2MSFTNGP03.phx.gbl...
Your client (or parent) form won't have released the instance, so the
instance count is not zero, and therefore it is not disposed. You won't
have an issue getting a property on the object from your instance.
"Dan Tallent" <sp**@microsoft.comwrote in message
news:e$**************@TK2MSFTNGP04.phx.gbl...
>Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the
parent?
Thanks
Dan
"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
>>On Mon, 01 Sep 2008 11:50:46 -0700, Dan Tallent <sp**@microsoft.com>
wrote:
[...]
I have code where I've added a custom event to the child form called
ReturnValueSet. The form that opens this form can then subscribe to
this
event and trap the value that was set if it wishes. The child form
then
must be coded to raise this event when it is closing. This method
works,
but I would prefer to use a more standard approach is there is one.
If you just want the client form to retrieve the value when the child
form is closed, then I'd say the client form should just subscribe to
the FormClosed event. Then the child form should set some property that
the client form can retrieve when the FormClosed event is raised (the
child form would of course make sure this property is suitably set when
it's closed, before the FormClosed event is raised).
That said, other than the name of the event, what you've done is
actually a reasonably standard approach, depending on the semantics you
want. The .NET convention would be to have a property, and then an
event with the same name as the property, plus "Changed".
You could either only raise the "Changed" event when the form closes, or
you could allow for the client form to monitor changes as the user
provides input. Either way, that would be reasonable too.
Pete
On Mon, 01 Sep 2008 12:38:19 -0700, Dan Tallent <sp**@microsoft.comwrote:
Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
As Mike says, the object itself will still be around (though not for the
reason he states). However, it is true that the form will have been
disposed by that time, so your property should not access the things
within the form that themselves are disposed when the form is disposed (in
particular, the various controls).
Typically, you'd address this by keeping the data of interest in a member
field that is updated either as the user provides input to the form, or by
simply initializing it in the OnFormClosing() override in the child form
(depending on when you want the property to be valid).
If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the
parent?
The FormClosed event is raised by the base OnFormClosed() method. The
OnFormClosing() method is called before the OnFormClosed(), so assuming
that's where you initialize the property, it will be valid when an event
raised by OnFormClosed() is raised, regardless of where in OnFormClosed()
you raise the event. If you somehow initialize the property in
OnFormClosed(), you'll want to do so before calling the base
OnFormClosed().
Pete
Peter, I think I follow what you are saying, but didn't realize that was
happening behind the scenes. Thanks for educating me today!
Mike
"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
On Mon, 01 Sep 2008 12:38:19 -0700, Dan Tallent <sp**@microsoft.com>
wrote:
>Thanks for the quick response.
If I use the FormClosed event does this cause a potential issue that the
form may of already been released and therefore the property being
unavailable?
As Mike says, the object itself will still be around (though not for the
reason he states). However, it is true that the form will have been
disposed by that time, so your property should not access the things
within the form that themselves are disposed when the form is disposed (in
particular, the various controls).
Typically, you'd address this by keeping the data of interest in a member
field that is updated either as the user provides input to the form, or by
simply initializing it in the OnFormClosing() override in the child form
(depending on when you want the property to be valid).
>If using the FormClosed event is safe, do you know if the code within the
child forms FormClosed event fires before it raises the event to the
parent?
The FormClosed event is raised by the base OnFormClosed() method. The
OnFormClosing() method is called before the OnFormClosed(), so assuming
that's where you initialize the property, it will be valid when an event
raised by OnFormClosed() is raised, regardless of where in OnFormClosed()
you raise the event. If you somehow initialize the property in
OnFormClosed(), you'll want to do so before calling the base
OnFormClosed().
Pete
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