DevExpress GridControl SummaryItem的Custom Summary

转自:http://blog.vsharing.com/janezhangxy/A1453525.html

使用DevExpress GridControl 时，有一栏为colSelected(FieldName 为"Selected") ,需根据此栏是否选中来计算另外一栏colCurrentApplyQuantity(FieldName 为"CurrentApplyQuantity")的Summary.

      依据默认的SummaryItem是无法实现的，需要使用Custom Aggregate Functions. 具体处理过程如下：

      1.设置Gridview OptionsView ShowFooter 为True，用来显示最终的Summary。

      2.设置colCurrentApplyQuantity 的SummaryType为Custome ,Tag 为1.Tag是用来区分SummaryItem.如需要格式化显示的结果，可设置相应的DisplayFormat.

     3.使用gridView1_CustomSummaryCalculate事件来实现依据colSelected来colCurrentApplyQuantity的Summary。 求和包括3个阶段，Initialization, Calculation 和Finalization。依据 CustomSummaryEventArgs.SummaryProcess的值来决定当前进行的那个阶段。具体实现如下：

 int customSum;
        private void gridView1_CustomSummaryCalculate(object sender, DevExpress.Data.CustomSummaryEventArgs e)
        {
            int summaryID = Convert.ToInt32((e.Item as GridSummaryItem).Tag);
            GridView gridView = sender as GridView;      
            // Initialization 
            if (e.SummaryProcess == CustomSummaryProcess.Start)
            {
               customSum = 0;
            }
            // Calculation 
            if (e.SummaryProcess == CustomSummaryProcess.Calculate)
            {
                bool isSelected = (bool)gridView.GetRowCellValue(e.RowHandle, "Selected");
                switch (summaryID)
                {
                    case 1: // The total summary calculated against the 'CurrentApplyQuantity' column. 
                        if (isSelected) customSum += Convert.ToInt32(e.FieldValue);                      
                        break;              
                }
            }
            // Finalization 
            if (e.SummaryProcess == CustomSummaryProcess.Finalize)
            {
                switch (summaryID)
                {
                    case 1:
                        e.TotalValue = customSum;
                        break;
                }
            }      
        }