Gridview get difference between two sums

Question

I'm using devexpress XtraGrid control. My problem is the following: I want to get the sum of the first column, and then the second column. I eventually want to subtract the sum of the first column of the sum of the second columns and to display the grid in the footer ...

Sum1Columns - Sum2Columns = balance

And then show balance on data grid control - footer (below the 1column)

dgvVIEW.Columns(1).Name = "PROMDUGU"
dgvVIEW.Columns(1).Caption = "1COLUMN"
dgvVIEW.Columns(1).Visible = True
dgvVIEW.Columns(1).DisplayFormat.FormatType = FormatType.Numeric
dgvVIEW.Columns(1).DisplayFormat.FormatString = "c2"
dgvVIEW.Columns(1).SummaryItem.SummaryType = DevExpress.Data.SummaryItemType.Custom
dgvVIEW.Columns(1).SummaryItem.SummaryType = DevExpress.Data.SummaryItemType.Sum
dgvVIEW.Columns(1).SummaryItem.DisplayFormat = "SUM= {0:n2}"

dgvVIEW.Columns(2).Name = "PROMPOTR"
dgvVIEW.Columns(2).Caption = "2COLUMN"
dgvVIEW.Columns(2).Visible = True
dgvVIEW.Columns(2).DisplayFormat.FormatType = FormatType.Numeric
dgvVIEW.Columns(2).DisplayFormat.FormatString = "c2"
dgvVIEW.Columns(2).SummaryItem.SummaryType =  DevExpress.Data.SummaryItemType.Sum
dgvVIEW.Columns(2).SummaryItem.DisplayFormat = "Sum= {0:n2}"

Answer 1

Add another summary field to 2nd column and set its type to custom.

dgvVIEW.Columns(2).Summary.Add(new GridColumnSummaryItem(SummaryItemType.Custom, "customBalance", "Balance= {0:c2}"));

Then handle CustomSummaryCalculate event.

private void dgvVIEW_CustomSummaryCalculate(object sender, CustomSummaryEventArgs e) {
    if (e.SummaryProcess == CustomSummaryProcess.Start) {
      this.sum1 = 0; // <--- class member !
      this.sum2 = 0; // <--- class member !
      return; 
    }

    if (e.SummaryProcess == CustomSummaryProcess.Calculate) {
      if (e.Item.FieldName == "PROMDUGU" {
        this.sum1 += Convert.ToDecimal(e.FieldValue);
        return;
      } 
      if (e.Item.FieldName == "PROMPOTR" {
        this.sum2 += Convert.ToDecimal(e.FieldValue);
        return;
      } 
      return; 
    }


    if (e.SummaryProcess == CustomSummaryProcess.Finalize && e.Item.FieldName == "customBalance") {
       e.TotalValue = sum1 - sum2;
    }
}