PRB: Null Values Disappear When Selected in a Grid or Browse (132331)
The information in this article applies to:
- Microsoft Visual FoxPro for Windows 3.0
This article was previously published under Q132331 SYMPTOMS
The text string ".NULL." for null values disappears when the field is
selected. When you move out of the field, ".NULL." reappears. This is by
design.
RESOLUTION
To display a text string ".NULL." for the currently selected field, create
a column class that displays a label with the text string ".NULL." via the
column's DynamicCurrentControl property. Copy the following code into
TESTNULL.PRG, and then run it. You will see a grid with one column and 10
rows. Some of the rows contain numeric values, and some contain ".NULL." as
a text string. Press DOWN ARROW to move through the records, note that the
text string value of ".NULL." is displayed when the pointer is on a record
that contains a null value.
PUBLIC oForm
oForm = CREATEOBJECT('myform')
oForm.SHOW
DEFINE CLASS mytextbox AS textbox
SpecialEffect = 1
BorderStyle = 0
FontBold = .F.
PROCEDURE keypress
LPARAMETERS nKeyCode, nShiftAltCtrl
IF nKeyCode = 48
REPLACE testnull.name WITH .NULL.
This.Value = ".NULL."
NODEFAULT
ENDIF
ENDPROC
ENDDEFINE
DEFINE CLASS mytextbox1 AS mytextbox
ControlSource = "testnull.name"
ENDDEFINE
DEFINE CLASS mytextbox2 AS mytextbox
ControlSource = "This.Value"
Value = ".NULL."
PROCEDURE gotfocus
This.Value = ".NULL."
ENDPROC
PROCEDURE lostfocus
IF This.Value <> ".NULL."
REPLACE testnull.name WITH This.Value
ENDIF
ENDPROC
ENDDEFINE
DEFINE CLASS mycolumn AS column
DynamicCurrentControl = "IIF(ISNULL(testnull.name),'text2', 'text1')"
Sparse = .f.
Bound = .f.
ADD OBJECT text1 AS mytextbox1
ADD OBJECT text2 AS mytextbox2
ENDDEFINE
DEFINE CLASS mygrid AS grid
RecordSource = ALIAS()
ADD OBJECT c1 AS mycolumn
ENDDEFINE
DEFINE CLASS myform AS form
ADD OBJECT g1 AS mygrid
PROCEDURE load
DELETE FILE testnull.dbf
CREATE TABLE testnull (name c(10) NULL)
FOR cnt = 1 to 10
APPEND BLANK
REPLACE name WITH IIF(MOD(RAND()*100, 2) >=1, SYS(3), .NULL.)
ENDFOR
GO TOP
ENDPROC
PROCEDURE unload
CLOSE DATA ALL
ENDPROC
ENDDEFINE
STATUS
This behavior is by design.
Modification Type: | Major | Last Reviewed: | 2/15/2000 |
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Keywords: | KB132331 |
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