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GridView.CustomSummaryCalculate Event

Allows custom summary value calculation. Fires for summary items with SummaryType set to SummaryItemType.Custom.

Namespace: DevExpress.XtraGrid.Views.Grid

Assembly: DevExpress.XtraGrid.v25.1.dll

NuGet Packages: DevExpress.Win.Grid, DevExpress.Win.Navigation

#Declaration

[DXCategory("Data")]
public event CustomSummaryEventHandler CustomSummaryCalculate

#Event Data

The CustomSummaryCalculate event's data class is CustomSummaryEventArgs. The following properties provide information specific to this event:

Property Description
FieldValue Gets the processed field value.
GroupLevel Gets the nested level of the group whose summary value is being calculated.
GroupRowHandle Gets a value identifying the group row whose child data rows are involved in summary calculation.
IsGroupSummary Gets whether a group summary value is being calculated.
IsTotalSummary Gets whether a total summary value is being calculated.
Item Gets a summary item whose value is being calculated.
Mode Specifies how summaries are calculated - against all rows or for the selected rows.
Row Gets the currently processed row.
RowHandle Gets the handle of the processed row.
SummaryProcess Gets a value indicating calculation stage.
TotalValue Gets or sets the total summary value.
TotalValueReady Gets or sets whether the Calculation stage of the custom summary calculation process should be skipped.

The event data class exposes the following methods:

Method Description
GetGroupSummary(Int32, Object) Returns the value of the specified group summary for the specified group row.
GetValue(String) Returns the value in the specified field

#Remarks

The GridControl calculates predefined summary types (for example, MAX, MIN, COUNT, AVG, etc.) automatically. To implement custom summary logic, handle the CustomSummaryCalculate event.

Note

A summary is treated as custom if its GridSummaryItem.SummaryType property equals to SummaryItemType.Custom.

The grid raises the CustomSummaryCalculate event in three stages:

  1. Start

    The event fires with the e.SummaryProcess == CustomSummaryProcess.Start. Use this stage to initialize the e.TotalValue parameter.

  2. Calculate

    The event fires once for each data row (in total summaries) or group row (in group summaries), with e.SummaryProcess == CustomSummaryProcess.Calculate. Use e.RowHandle and e.FieldValue to access the row and value. Update e.TotalValue accordingly.

  3. Finalize

    After processing all rows, the event fires with e.SummaryProcess == CustomSummaryProcess.Finalize. Use this stage to finalize e.TotalValue.

See the following help topic for more information: Working with Summaries in Code. Custom Summaries.

#Specific Notes

#Server Mode

In Server Mode, the CustomSummaryCalculate event fires only once with e.CustomSummaryProcess == CustomSummaryProcess.Finalize. The event does not process individual data rows. Assign the final value to e.TotalValue directly.

gridView1.CustomSummaryCalculate += (obj, e) => {
    e.TotalValueReady = true;
    e.TotalValue = 100;
};

#Summary Field Not Represented by a Grid Column

If the summary item references a data field that is not displayed in the grid (for example, no column is bound to this field), the CustomSummaryCalculate event fires only twice — once with CustomSummaryProcess.Start and once with CustomSummaryProcess.Finalize. The CustomSummaryProcess.Calculate stage is skipped, as the grid does not iterate through data rows.

#Example

The example below creates a new custom summary items and populates it on the GridView.CustomSummaryCalculate event. You can test this sample in our DevExpress Demo Center (the link requires Demo Center of version 16.2 or newer to be installed).

Grid - Custom Total Summary

The custom summary item is located under the “Length” column. To add it, set up the GridColumn.SummaryItem property.

gridView.OptionsView.ShowFooter = true;
GridColumn column = gridView.Columns["Length"];
column.SummaryItem.SummaryType = SummaryItemType.Custom;

The CustomSummaryCalculate event handler checks the current calculation state by reading the CustomSummaryEventArgs.SummaryProcess value. Cell values are added to the total sum only if the corresponding cell under the “Mark” column is checked.

double sum = 0;
gridView.CustomSummaryCalculate += (sender, e) => {
    GridView view = sender as GridView;
    if (e.IsTotalSummary && (e.Item as GridSummaryItem).FieldName=="Length") {
        GridSummaryItem item = e.Item as GridSummaryItem;
        if (item.FieldName == "Length") {
            switch (e.SummaryProcess) {
                case CustomSummaryProcess.Start:
                    sum = 0;
                    break;
                case CustomSummaryProcess.Calculate:
                    bool shouldSum = (bool)view.GetRowCellValue(e.RowHandle, "Mark");
                    if (shouldSum) {
                        sum += (double)e.FieldValue;
                    }
                    break;
                case CustomSummaryProcess.Finalize:
                    e.TotalValue = sum;
                break;
            }
        }
    }
};

To automatically update the summary item when users check or clear the “Mark” column checkboxes, the GridView.UpdateTotalSummary method is called on the RepositoryItem.EditValueChanged event.

RepositoryItemCheckEdit edit = gridView.Columns["Mark"].RealColumnEdit as RepositoryItemCheckEdit;
edit.EditValueChanged += (sender, e) => {
    //Post an editor's value to a data source
    gridView.PostEditor();
    //Force calculation of the total summary
    gridView.UpdateTotalSummary();
};

The code below is a complete example code.

    // Handle this event to calculate summary values manually
    double sum = 0;
    gridView.CustomSummaryCalculate += (sender, e) => {
        GridView view = sender as GridView;
        if (e.IsTotalSummary && (e.Item as GridSummaryItem).FieldName=="Length") {
            GridSummaryItem item = e.Item as GridSummaryItem;
            if (item.FieldName == "Length") {
                switch (e.SummaryProcess) {
                    case CustomSummaryProcess.Start:
                        sum = 0;
                        break;
                    case CustomSummaryProcess.Calculate:
                        bool shouldSum = (bool)view.GetRowCellValue(e.RowHandle, "Mark");
                        if (shouldSum) {
                            sum += (double)e.FieldValue;
                        }
                        break;
                    case CustomSummaryProcess.Finalize:
                        e.TotalValue = sum;
                        break;
                }
            }
        }
    };

    gridView.OptionsView.ShowFooter = true;
    GridColumn column = gridView.Columns["Length"];
    column.SummaryItem.SummaryType = SummaryItemType.Custom;

    RepositoryItemCheckEdit edit = gridView.Columns["Mark"].RealColumnEdit as RepositoryItemCheckEdit;
    edit.EditValueChanged += (sender, e) => {
        //Post an editor's value to a data source
        gridView.PostEditor();
        //Force calculation of the total summary
        gridView.UpdateTotalSummary();
    };
See Also