Devexpress Gridview 自定義彙總CustomSummaryCalculate（加權平均）

        Devexpress Gridview 提供了簡單的求和，平均等方法，複雜的彙總方法則需要自定義，使用gridview 的CustomSummaryCalculate 事件，根據官網的文檔及各論壇案例實現加權平均的方法。 

gridView1.CustomSummaryCalculate += new CustomSummaryEventHandler(view_CustomSummaryCalculate);

　　自定義彙總方法（加權平均）

 
 3 // 顯示記錄數量
 4 GridColumnSummaryItem siTotal = new GridColumnSummaryItem();
 5 siTotal.SummaryType = SummaryItemType.Count;
 6 siTotal.DisplayFormat = "{0} records";
 7 
 8 // 對 Length 欄位列 彙總平均    
 9 GridColumnSummaryItem siAverage = new GridColumnSummaryItem();
10 siAverage.SummaryType = SummaryItemType.Average;
11 siAverage.FieldName = "Length";
12 siAverage.DisplayFormat = "Average: {0:#.#}"; 
14     
15 // gridView1中colIdRandom 列顯示多行彙總：最小、計數、加權平均    
16 this.colIdRandom.Summary.AddRange(new DevExpress.XtraGrid.GridSummaryItem[] {
17      new DevExpress.XtraGrid.GridColumnSummaryItem(DevExpress.Data.SummaryItemType.Min, "IdRandom", "MIN={0}", "Min"),
18      new DevExpress.XtraGrid.GridColumnSummaryItem(DevExpress.Data.SummaryItemType.Count, "IdRandom", "Count = {0}", "Count"),
19      new DevExpress.XtraGrid.GridColumnSummaryItem(DevExpress.Data.SummaryItemType.Custom, "IdRandom", "Custom Summary = {0}")});
20 // 計算加權平均    
21 CalacWeightAverage(gridView1,"WeightColumn","TEST1",colIdRandom.FieldName);
22 
23 // 彙總項目綁定到相應列，顯示在view footer
24 gridView1.Columns["ID"].SummaryItem.Collection.Add(siTotal);
25 gridView1.Columns["Length"].SummaryItem.Collection.Add(siAverage);
26 gridView1.OptionsView.ShowFooter = true;
27 
28 
29 double sumWt=0;
30 double customSummaryValue;
31 string WeightColumn;
32 
33 void CalacWeightAverage(DevExpress.XtraGrid.Views.Grid.GridView view, string weightColumn, params string[] weightAverageColumns)
34 {    
35     WeightColumn = weightColumn;
36     if (view.Columns.ColumnByFieldName(weightColumn) != null)
37     {
38         if (!(view.Columns[weightColumn].ColumnType != typeof(decimal)) 
39             || !(view.Columns[weightColumn].ColumnType != typeof(int)))
40         {
41             for (int i = 0; i < weightAverageColumns.Length; i++)
42             {
43                 string fieldName = weightAverageColumns[i];
44                 if (view.Columns.ColumnByFieldName(fieldName) != null 
45                     && (!(view.Columns[fieldName].ColumnType != typeof(decimal)) 
46                     || !(view.Columns[fieldName].ColumnType != typeof(int))))
47                 {
48                     view.Columns[fieldName].SummaryItem.SummaryType = SummaryItemType.Custom;
49                     GridSummaryItem gridSummaryItem = view.GroupSummary.Add(SummaryItemType.Custom, fieldName, view.Columns[fieldName]);
50                     gridSummaryItem.DisplayFormat = view.Columns[fieldName].SummaryItem.DisplayFormat;
51                 }
52             }
53         //gridView1.CustomSummaryCalculate += new CustomSummaryEventHandler(gridView1_CustomSummaryCalculate);    
54         }
55     }
56 }
57 
  // 自定義彙總演算法
58 void gridView1_CustomSummaryCalculate(object sender, CustomSummaryEventArgs e)
59 {            
60     if (e.Item != null)
61     {
62         //if (e.IsGroupSummary) {} 分組彙總
63         //if (e.IsTotalSummary) {} 全部彙總
64      
65         var gridView = sender as DevExpress.XtraGrid.Views.Grid.GridView;
66         if (gridView.Columns.ColumnByFieldName(WeightColumn) != null)
67         {
68             GridSummaryItem gridSummaryItem = e.Item as GridSummaryItem;
69             if (e.SummaryProcess == CustomSummaryProcess.Start)
70             {
71                 customSummaryValue = 0;
72                 sumWt = 0;
73             }
74             else if (e.SummaryProcess == CustomSummaryProcess.Calculate)
75             {
76                 if (e.FieldValue != null && e.FieldValue != DBNull.Value)
77                 {
78                     sumWt += Convert.ToDecimal(gridView.GetRowCellValue(e.RowHandle, WeightColumn));
79                     customSummaryValue += Convert.ToDecimal(e.FieldValue) * Convert.ToDecimal(gridView.GetRowCellValue(e.RowHandle, WeightColumn));
80                 }
81             }
82             else if (e.SummaryProcess == CustomSummaryProcess.Finalize)
83             {
84                 e.TotalValue = ((sumWt == 0) ? 0 : (customSummaryValue / sumWt));
85             }
86         }
87     }
88 }

參考資料：

https://documentation.devexpress.com/WindowsForms/701/Controls-and-Libraries/Data-Grid/Summaries/Working-with-Summaries-in-Code

https://documentation.devexpress.com/CoreLibraries/DevExpress.Data.CustomSummaryEventArgs.class

https://www.cnblogs.com/EasyInvoice/p/3892136.html