When a column is added to or removed from a list, the associated Column object is added to or removed from the list's Columns collection. This may cause a change in the index numbers of the existing columns, making it very inconvenient to reference columns numerically. For this reason, True DBList also allows you to reference columns using either the DataField or Caption strings. Thus, the following references are identical:

TDBList1.Columns(n)           ' Reference by the Column index

TDBList1.Columns("LAST")      ' Reference by the DataField name

TDBList1.Columns("Last Name") ' Reference by the Caption string

Referencing column objects by DataField or Caption is not case-sensitive. TDBList1.Columns("LAST") refers to the same column as TDBList1.Columns("last").

When you reference a Column object and its properties at run time, Visual Basic creates an instance of the object. For example, if you duplicate certain properties of a column:

TDBList1.Columns("First").Width = _

    TDBList1.Columns("Last").Width

TDBList1.Columns("First").Alignment = _

    TDBList1.Columns("Last").Alignment

TDBList1.Columns("First").AllowSizing = _

    TDBList1.Columns("Last").AllowSizing

The Columns("First") and Columns("Last") objects will each be created and discarded three times in the preceding example. The same results are achieved more efficiently by creating object variables that refer to these columns:

' Declare Column objects

Dim FirstCol As TrueDBList80.Column

Dim LastCol As TrueDBList80.Column

 

' Reference First and Last Column objects

Set FirstCol = TDBList1.Columns("First")

Set LastCol = TDBList1.Columns("Last")

 

' Copy properties from Last to First

FirstCol.Width = LastCol.Width

FirstCol.Alignment = LastCol.Alignment

FirstCol.AllowSizing = LastCol.AllowSizing

The same technique can be applied to other objects in Visual Basic. For more details, see Object Model.

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