TcxSummaryEvent Type

The procedural type for summary calculation events.

Declaration

TcxSummaryEvent = procedure(ASender: TcxDataSummaryItems; Arguments: TcxSummaryEventArguments; var OutArguments: TcxSummaryEventOutArguments) of object;

Parameters

Name	Type	Description
ASender	TcxDataSummaryItems	The summary item collection that raised the summary calculation event.
Arguments	TcxSummaryEventArguments	Provides access to summary calculation arguments. You can use Arguments.SummaryItem and Arguments.RecordIndex fields to identify the calculated summary item and its source record in the parent data controller.
OutArguments	TcxSummaryEventOutArguments	Provides access to summary calculation results. You can assign True to the OutArguments.Done field to exclude the currently processed record value from summary calculation.

Remarks

A summary calculation event occurs for every processed record. You can handle this event to override or modify a predefined summary calculation algorithm.

Code Examples

Exclude Null Values from Summary Calculation

The following code example excludes all Null Variant record values from summary calculation:

Delphi

procedure TMyForm.cxGrid1DBTableView1DataControllerSummaryDefaultGroupSummaryItemsSummary(
  ASender: TcxDataSummaryItems; Arguments: TcxSummaryEventArguments;
  var OutArguments: TcxSummaryEventOutArguments);
begin
  if (VarIsNull(OutArguments.Value)) then // If the currently processed value is Null Variant
    OutArguments.Done := True;  // Ignores the Null Variant record value
end;

C++

void __fastcall TMyForm::cxGrid1DBTableView1DataControllerSummaryDefaultGroupSummaryItemsSummary(
  TcxDataSummaryItems *ASender, TcxSummaryEventArguments &Arguments,
  TcxSummaryEventOutArguments &OutArguments) {
  if (VarIsNull(OutArguments.Value)) {  // If the currently processed value is Null Variant
    OutArguments.Done = true;  // Ignores the Null Variant record value
  }
}

Custom Summary Calculation

All predefined summary calculation algorithms use record values of only one data item. The OnSummary event allows you to modify a predefined summary calculation algorithm in any manner. For example, you can use values of multiple data items in every iteration of the summary calculation process.

The code example below demonstrates an OnSummary event handler that modifies the predefined algorithm MAX. The event handler calculates the highest population density based on data-aware grid columns that display country areas (DBTableView1Area) and corresponding population values (DBTableView1Population):

Delphi

procedure TMyForm.cxGrid1DBTableView1DataControllerSummaryDefaultGroupSummaryItemsSummary(
  ASender: TcxDataSummaryItems; Arguments: TcxSummaryEventArguments;
  var OutArguments: TcxSummaryEventOutArguments);
var
  AArea, APopulation: Variant;
begin
  // Obtain the area value for the currently processed record
  AArea := ASender.DataController.Values[Arguments.RecordIndex, DBTableView1Area.Index];
  // Obtain the population value for the currently processed record
  APopulation := ASender.DataController.Values[Arguments.RecordIndex, DBTableView1Population.Index];
  OutArguments.Value := APopulation/AArea; // Calculates the custom summary value (maximum population density)
end;

C++

void __fastcall TMyForm::cxGrid1DBTableView1DataControllerSummaryDefaultGroupSummaryItemsSummary(
  TcxDataSummaryItems *ASender, TcxSummaryEventArguments &Arguments,
  TcxSummaryEventOutArguments &OutArguments) {
  // Obtain the area value for the currently processed record
  Variant AArea = ASender->DataController->Values[Arguments.RecordIndex][DBTableView1Area->Index];
  // Obtain the population value for the currently processed record
  Variant APopulation = ASender->DataController->Values[Arguments.RecordIndex][DBTableView1Area->Index];
  OutArguments.Value = APopulation/AArea;  // Calculates the custom summary value (maximum population density)
}

Direct TcxSummaryEvent Type References

The following events reference the TcxSummaryEvent procedural type:

TcxDataSummaryItems.OnSummary

Allows you to customize summary calculation.

TcxGridChartDataController.OnSummary

Occurs when calculating a specific summary value.

TcxGridDBChartDataController.OnSummary

Occurs when calculating a specific summary value.