代码之家 › 专栏 › 技术社区 › Drew Noakes

如何将加权平均摘要添加到devexpress xtragrid?

group-summaries weighted-average xtragrid devexpress .net

2

Drew Noakes · 技术社区 · 15 年前

devexpress网格(xtragrid)允许网格及其组进行汇总计算。可用选项有count、max、min、avg、sum、none和custom。

是否有人获得了一些示例代码,说明如何根据另一列中作为值提供的权重计算加权平均列?

2 回复 | 直到 13 年前

1

3

Drew Noakes 15 年前

我最终解决了这个问题,并将我的解决方案张贴在这里,以防其他人发现它有用。

如果加权平均值由每行的值和权重组成,则包含该值的列应将weight gridcolumn对象分配给其tag属性。然后,此事件处理程序将执行其余操作:

private static void gridView_CustomSummaryCalculate(object sender, CustomSummaryEventArgs e)
{
    GridColumn weightColumn = ((GridSummaryItem)e.Item).Tag as GridColumn;

    if (weightColumn == null)
        return;

    switch (e.SummaryProcess)
    {
        case CustomSummaryProcess.Start:
        {
            e.TotalValue = new WeightedAverageCalculator();
            break;
        }
        case CustomSummaryProcess.Calculate:
        {
            double size = Convert.ToDouble(e.FieldValue);
            double weight = Convert.ToDouble(((GridView)sender).GetRowCellValue(e.RowHandle, weightColumn));

            ((WeightedAverageCalculator)e.TotalValue).Add(weight, size);
            break;
        }
        case CustomSummaryProcess.Finalize:
        {
            e.TotalValue = ((WeightedAverageCalculator)e.TotalValue).Value;
            break;
        }
    }
}

private sealed class WeightedAverageCalculator
{
    private double _sumOfProducts;
    private double _totalWeight;

    public void Add(double weight, double size)
    {
        _sumOfProducts += weight * size;
        _totalWeight += weight;
    }

    public double Value
    {
        get { return _totalWeight==0 ? 0 : _sumOfProducts / _totalWeight; }
    }
}

代码假定基础列值可以通过 Convert.ToDouble(object) .

2

0

Tim Cooper 13 年前

如果在sum中提供自己的lambda表达式,那么应该能够用标准sum对它们进行分组。我认为这应该有效:

var grouped = from item in items
orderby item.Group
group item by item.Group into grp
select new
{
Average= grp.Sum(row => row.Value * row.Weight)
};