PRB: Controls Not Correctly Updated in a Grid

• Microsoft Visual FoxPro for Windows, version 3.0

SYMPTOMS

In a grid, as soon as you change the value of one control, the new value appears throughout the whole column. The expected behavior is that only one row displays the new value. Modifying the value of the Sparse property for this column has no effect on this behavior.

CAUSE

The control that is added to the column of the grid has no ControlSource. Therefore, when the value of the control is modified, there's no underlying variable, so the data is stored in the control itself. The same check box is populating the whole column in the grid. For example, one column of a grid contains a check box. If you click the check box on one row, the value of the check box will be modified. If the control does not have a controlsource, the new value will be propagated across all of the rows in the column.

The SPARSE property of the column object affects the display in the column. It does not control the value associated with the control.

STATUS

This behavior is by design.

RESOLUTION

Controls that are to display different values across a column of a grid need to be bound to data. You can set the Controlsource property of either the control or the column that contains the control to a field that will hold the value of the control.

MORE INFORMATION

The following sample program reproduces the behavior described in this article. To run this example, copy and paste the code into a program file. When the grid is displayed, click the check box. As you navigate through the grid, all of the rows will display the same value for the check box.

Steps to Reproduce Behavior

Run the following code:

   USE SYS(2004)+"SAMPLES\DATA\CUSTOMER"
   oMyform=CREATE ('MYFORM')
   oMyform.SHOW
   READ EVENTS

   DEFINE CLASS MYFORM AS FORM
     ADD OBJECT grdChecbox AS MYGRID
     ADD OBJECT cmdquit AS COMMANDQUIT
   ENDDEFINE

   DEFINE CLASS MYGRID AS GRID
     ADD OBJECT COLUMN1 AS COLUMN
     ADD OBJECT clmChk1 AS COLUMNCHECK
   ENDDEFINE

   DEFINE CLASS COLUMNCHECK AS COLUMN
     Bound=.f.
     Sparse=.f.
     ADD OBJECT CHK1 AS CHECKBOX
      CURRENTCONTROL="CHK1"
   ENDDEFINE

   DEFINE CLASS COMMANDQUIT as COMMANDBUTTON
     Caption="Quit"
     Top=208
     Left=58
     Height=20
     Width=45
     PROCEDURE  Click
       RELEASE thisform
       CLEAR EVENTS
     ENDPROC
   ENDDEFINE