Delphi DBGrid Record selection and reverse selection drag processing

Dbgrid1.dragmode: = dmmanual;//Note that this setting does not change

Procedure Applicationevents1message (var msg:tagmsg; var handled:boolean);

Procedure Tform18.applicationevents1message (Var msg:tagmsg;
var handled:boolean);
Begin
Case Msg.message of
Wm_lbuttondown:
Begin
If Msg.hwnd = Dbgrid1.handle Then
Begin
Dbgrid1.perform (Msg.message, Msg.wparam, Msg.lparam);
Dbgrid1.dragmode: = dmautomatic;
End
End
WM_LBUTTONUP:DBGrid1.DragMode: = dmmanual;
End
End

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Procedure Tform10.speedbutton7click (Sender:tobject);

Select All

begin
   with DBGrid1.datasource.dataset do
   begin
      first;
      while not DM. Aq_personal. eof   do
      begin
         DBGrid1.SelectedRows.CurrentRowSelected: = True;
         DM. Aq_personal. Next;
      end;
   end;
End;

Procedure Tform10.speedbutton8click (Sender:tobject);//Reverse Selection
Var
I:integer;
Saveplace:tbookmarklist;
Begin
DBGrid1.DataSource.DataSet.DisableControls;
For I:=1 to DBGrid1.DataSource.DataSet.RecordCount do
Begin
Dbgrid1.datasource.dataset.recno:=i;
Dbgrid1.selectedrows.currentrowselected:=not DBGrid1.SelectedRows.CurrentRowSelected;
End
Saveplace:=dbgrid1.selectedrows;
DBGrid1.DataSource.DataSet.GotoBookmark (Pointer (saveplace[0]));//point pointer to the first record of the current selection
DBgrid1.DataSource.DataSet.EnableControls;
End