Monday, 16 December 2013

Dataset EnableControls and DisableControls Methods in Delphi

Dataset EnableControls and DisableControls Methods in Delphi

EnableControls re-enables data display in data-aware controls associated with the dataset. Call EnableControls to permit data display in data-aware controls after a prior call to DisableControls. EnableControls decrements the disabled count variable for the dataset if it is not already zero. If the disable count variable is zero, EnableControls updates the current state of the dataset, if necessary, and then tells associated controls to re-enable display. 

Usually DisableControls is called within the context of a try...finally block that re-enables the controls even if an exception occurs.

Simple Delphi Example to show the usage of EnableControls and DisableControls

procedure TForm1.Button1Click(Sender: TObject);
var
  i: Integer;
begin
  ListBox1.Clear;
  ListBox1.Items[0]:= 'Destination Airports:';
  with Flights do
  begin
    DisableControls;
    try
      First;
      i:= 1;
      ListBox1.Items[0]:= 'Destination Airports:';
      while not Eof do
      begin
        ListBox1.Items[i]:= Fields[2].Value;;
        i:= i + 1;
        Next;
      end;
    finally
      EnableControls;
    end;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  Flights:= TTable.Create(Form1);
  with Flights do
  begin
    TableName := 'Flights';
    DatabaseName := 'databasepath';
  end;
  DS2.DataSet:= Flights;
  DBGrid2.DataSource.DataSet:= Flights;
  Flights.Active:= True;
end;

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