CheckBox returning a Null value - is it a common thing?

  • Thread starter Thread starter Morris
  • Start date Start date
M

Morris

Hi all,

I know a checkbox is supposed to return a True (-1) value when in
selected state or False (0) value when in unselected state. And that
works fine.

The problem is that right after opening the form the CheckBox is
unselected by default but it's got no value - it returns Null and
isnull(me.check15) returns True.

Is this a correct behaviour? Should I have a OnLoad event which makes
all the checkboxes False?

Thanks for help
Morris
 
hi Morris,
Is this a correct behaviour? Should I have a OnLoad event which makes
all the checkboxes False?
Click to expand...
You may set the DefaultValue property to True or False depending on your
logic behind it.


mfG
--> stefan <--
 
Morris said:
Hi all,

I know a checkbox is supposed to return a True (-1) value when in
selected state or False (0) value when in unselected state. And that
works fine.

The problem is that right after opening the form the CheckBox is
unselected by default but it's got no value - it returns Null and
isnull(me.check15) returns True.

Is this a correct behaviour? Should I have a OnLoad event which makes
all the checkboxes False?
Click to expand...


If the check box is unbound, then it will have a Null value until you set
it, unless you've given it a default value. If it's bound to a boolean
(yes/no) field, it can't have a Null value unless that field is on the
unmatched side of an outer join, because the Jet database engine can't store
Null in a boolean field. If it's bound to some other type of field, an
Integer field for example, then the field could have a Null value and the
check box will reflect it.
 
If the check box is unbound, then it will have a Null value until you set
it, unless you've given it a default value. If it's bound to a boolean
(yes/no) field, it can't have a Null value unless that field is on the
unmatched side of an outer join, because the Jet database engine can't store
Null in a boolean field. If it's bound to some other type of field, an
Integer field for example, then the field could have a Null value and the
check box will reflect it.
Click to expand...

Thanks both of you for an exhausting explanation.

At first I assumed there must be a 'DefaultValue' setting for this
control but to my surprise there wasn't any. That's why I posted this
question here. Obviously as you know after I clicked the checkbox, by
default both checkbox and corresponding lable were selected, giving me
properties of a label. Now I've set a DefaultValue = False (as it's
unbound) and everything works great,

Thanks once again!
Morris
 
Back
Top