Example 2: TcxDataSummaryItems.OnSummary

• Jul 29, 2021
• 2 minutes to read

A summary calculation involves iteration of item elements within a group and evaluation of a specific number (the number of item elements, sum, the maximum value etc.). It is possible to substitute an element value when calculating a summary.

Let us suppose that you have a table which represents information on the country population and area. To calculate the maximum density of population within a group of records you can use a summary of the skMax type and write the TcxDataSummaryItems.OnSummary event as follows. See the Creating Summaries topic regarding how to set summaries for a grid control.

Delphi

procedure TForm1.cxGrid1DBTableView1TcxGridDBDataControllerTcxDataSummary
DefaultGroupSummaryItemsSummary(
  ASender: TcxDataSummaryItems; Arguments: TcxSummaryEventArguments;
  var OutArguments: TcxSummaryEventOutArguments);
var
  AArea, APopulation: Extended;
begin
  //Locate a value in the specific record for Area item
  AArea := ASender.DataController.Values[Arguments.RecordIndex, DBTableView1Area.Index];
  //Locate a value in the specific record for Population item
  APopulation := ASender.DataController.Values[Arguments.RecordIndex, DBTableView1Population.Index];
  //Set population density to Value
  OutArguments.Value := APopulation / AArea;
end;

C++

void __fastcall TForm1::cxGrid1DBTableView1TcxGridDBDataControllerTcxDataSummary
DefaultGroupSummaryItemsSummary(
  TcxDataSummaryItems *ASender, TcxSummaryEventArguments &Arguments,
  TcxSummaryEventOutArguments &OutArguments) {
  //Locate a value in the specific record for Area item
  long double AArea = double(ASender->DataController->Values[Arguments.RecordIndex][0]);
  //Locate a value in the specific record for Population item
  long double APopulation = double(ASender->DataController->Values[Arguments.RecordIndex][0]);
  //Set population density to Value
  OutArguments.Value = double(APopulation / AArea);
end;