How To Change a Grid's RecordSource Property Programmatically

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0

SUMMARY

This article shows by example how to change the RecordSource property of a grid programmatically. It also allows you to click the column heading to change the order of the table.

MORE INFORMATION

The method that does most of the work is SetGrid. It allows the user to select a table from an Open File dialog box. It sets the RecordSource property of the grid and the column headings to the field names in the table. It removes the any extra columns if the tables differ in the number of the fields they contain.

The order is set in the Click event of the header. Setting the order by clicking the column header can only be done programmatically because it requires a subclass of the header. Columns and headers can only be subclassed in code.

When the following code is run, the user will be presented with a dialog box to select a table. After table selection, the form appears. To change the table on which the grid is based, the user can click the button and they will again be presented with a dialog box to select a table.

Code Sample

* Begin Code PUBLIC oGridForm oGridForm = CREATEOBJECT("myForm") oGridForm.Show

DEFINE CLASS myForm AS FORM

    Height = 350
    ADD OBJECT myGrid AS myGrid WITH Top = 20, LEFT = 20,;
      Height = 200
    ADD OBJECT myCommand as COMMANDBUTTON WITH Top = 250,;
      Left = 20, Height = 30, Caption = "Change Grid"

    PROCEDURE myCommand.Click
        This.Parent.myGrid.SetGrid()
        GO TOP
        ThisForm.ReFresh
    ENDPROC

DEFINE CLASS myGrid AS GRID

    ColumnCount = 0

    PROCEDURE Init
        This.Parent.myGrid.SetGrid()
        ThisForm.Refresh
    ENDPROC

    PROCEDURE SetGrid
        ThisForm.Lockscreen = .T.
        lcFileName = GETFILE("DBF","Select the Table:")
        USE (lcFileName)
        lcAlias = ALIAS()
        This.RecordSource = ""
        This.RecordSource = lcAlias
        SELECT (lcAlias )
        FOR i = 1 TO FCOUNT()
            IF This.ColumnCount < i
               This.AddObject("column" + ALLTRIM(STR(i)),"MyColumn")
            ENDIF
            This.Columns(i).Visible = .t.
            This.Columns(i).ControlSource = FIELD(i)
            This.Columns(i).Header1.Caption = FIELD(i)
        ENDFOR
        FOR i = FCOUNT() + 1 TO This.ColumnCount
            This.RemoveObject("Column"+ALLTRIM(STR(i)))
        ENDFOR
        ThisForm.Caption = lcAlias
        ThisForm.Lockscreen = .F.
     ENDPROC

DEFINE CLASS myColumn as Column

    ADD OBJECT Header1 as myHeader WITH Visible = .T.

DEFINE CLASS myHeader AS HEADER

    PROCEDURE Click
       FOR nCount = 1 TO 254
           IF !EMPTY(TAG(nCount))
              IF This.Caption = TAG(nCount)
                 SET ORDER TO This.Caption
                 EXIT
              ENDIF
           ELSE
              EXIT
           ENDIF
       ENDFOR
       This.Parent.Parent.ReFresh
       This.Parent.Parent.SetFocus
    ENDPROC