first and last row in a DBGrid

[Stark]

On the push of a button by the user, I would like to make changes to all of
the records of a dataset curenly visible on a DBGrid.
I need a way to identify the visible rows in order to apply a filter or run
a query on the dataset. How do I know the first and the last DBGrid rows ?

[alang...@aol.com]

From TDBGrid's ancestor . . .

TCustomGrid >> TDBGrid.TopRow
TCustomGrid >> TDBGrid.VisiblrRowCount

Alan Lloyd

[Stark]

I don't find these properties anywhere, Alan.
Can you be more explicit ? Thanks

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[alang...@aol.com]

On 11 Feb, 15:14, "Stark" <franco.jo...@tin.it> wrote:
> I don't find these properties anywhere, Alan.
> Can you be more explicit ? Thanks

Look in Delphi Help for TDBGrid and Heirarchy. You will see that
TDBGrid is descended from TCustomDBGrid & TCustom Grid. Click on
TCustomGrid & then click on Properties in TCustomGrid. You will see
TopRow & VisibleRowCount in the list with (in D3) a yellow square
showing they are Protected properties.

Protected properties are not exposed (ie made available) except
explicitly by a descendant class _OR_ by typecasting to a new
descendant class. So you cannot (as you have found) access them as
properties of a TDBGrid.

But you can access them by declaring a descendant class of TDBGrid
(any name but I usually use a name meaningful for the purpose) :-

class
TDBGridRows = class(TDBGrid);

Then you can access the properties by :-

MyTopRow := TDBGridRows(TDBGrid).TopRow;
MyVisibleRows := TDBGridRows(TDBGrid).VisibleRowCount;

Protected & private properties are always there, but the compiler
prevents you accessing them unless you cheat <g>.

Alan Lloyd

[Stark]

Thanks a lot. You have the gift of concreteness and clarity.

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