Linq Sum与group by [英] Linq Sum with group by

问题描述

我有一个带有列的表结构

I am having a table structure with columns

收费普通

FeesCustom

FeesCustom

货币

现在我正在按货币查找SUM函数组.

Now i am looking for a SUM function group by currency .

例如，此表中的价格为20 USD + 30 EURO + 40 INR

For example 20 USD + 30 EURO + 40 INR something like this from this table

如果FeesCustom> 0，我还必须考虑这种情况，我必须忽略该行的FeesNormal

I also have to consider the scenario if FeesCustom > 0 I have to ignore FeesNormal for the row

采样日期和预期结果是这样

Sample date and expected result is like this

  FeesNormal  FeesCustom  Currency
  10          0            USD   
  15          25           USD //in this case can ignore FeesNormal Since FeesCustom is more
  5           10           EUR //same for this row ignore FeesNormal
  10          0            EUR

Expected result  35 USD 20 EUR   

我可以使用linq找到总和

I able to find sum using the linq

 int sum_custom=(int)fee_list.Where(p => p.FeesCustom > 0).Sum(p => p.FeesCustom);
 int sum_normal = (int)fee_list.Where(p => p.FeesCustom ==0).Sum(p => p.FeesNormal);

推荐答案

在我看来，您只需要一个从入账"到有效费用"的投影，您可以将其相加-类似于:

It seems to me that you just need a projection from "entry" to "effective fee" which you can sum - something like:

var result = source
    .GroupBy(x => x.Currency)
    .Select(g => new {
        Currency = g.Key,
        Total = g.Sum(x => x.FeesCustom > 0 ? x.FeesCustom : x.FeesNormal)
    });

等同于:

var result = source
    .GroupBy(x => x.Currency,
             (key, values) => new {
                Currency = key,
                Total = values.Sum(x => x.FeesCustom > 0 ? x.FeesCustom : x.FeesNormal)
             });

或者更早进行转换:

 var result = source
     .Select(x => new {
         x.Currency,
         x.Fee = x => x.FeesCustom > 0 ? x.FeesCustom : x.FeesNormal
     })
     .GroupBy(x => x.Currency, x => x.Fee,
              (key, values) => new { Currency = key, Fee = values.Sum() });

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