如何对数据表列求和并得到差异 [英] how to sum data table column and get the diffrence

问题描述

你好..

i需要制作一个这样的数据表：

hello ..
i need to make a data table like that:

Subjects          old        new    diff
Sub_1             10         50     40
Sub_2             30         10     -20
total             40         60     20

这是一个部分代码

this is a part of code

DataTable subjects = new DataTable();
    subjects.Columns.Add("Subjects");
    subjects.Columns.Add("old");
    subjects.Columns.Add("new");
    subjects.Columns.Add("diff");
subjects.Rows.Add("Sub_1", sub1.Old    , sub1.New    , (sub1.New - sub1.Old));
subjects.Rows.Add("Sub_2", sub2.Old    , sub2.New    , (sub2.New - sub2.Old));
subjects.Rows.Add("Total", .. total of above    .. , .. total of above    .., .. total of above  ..);

所以我需要问一下如何计算最后一列的总价值（总计），还有其他方法来计算第四列库存（3rdcol - 2 2nd col）

so i need to ask how to calculate the total value of last column ( Total) , and is there is any other way to calculate the 4th coulmn ( 3rdcol - 2 2nd col )

推荐答案

添加一个对当前行中的总计进行操作的计算列非常简单：您不必自己进行数学运算，表格可以为您完成：

Adding a calculated column which operates on the totals in the current row is easy: You don't have to do the math yourself, the table can do that for you:

DataTable subjects = new DataTable();
subjects.Columns.Add("Subjects");
subjects.Columns.Add("old", typeof(int));
subjects.Columns.Add("new", typeof(int));
subjects.Columns.Add("diff", typeof(int), "new-old");
subjects.Rows.Add("Sub_1", 50, 60);
subjects.Rows.Add("Sub_2", 100, 46);

但是没有自动生成总行AFAIK的方法。

你可以手动完成：

But there is no automatic way to generate a totals row AFAIK.
You can do it manually:

subjects.Rows.Add("TOTAL", subjects.Compute("Sum(old)", ""), subjects.Compute("Sum(new)", ""), subjects.Compute("Sum(diff)", ""));

但是赢了; t自动更新 - 每次单元格更改或添加/删除行时都必须重新运行计算。

But that won;t update itself automaticaaly - you will have to re-run the Computes each time a cell changes or a row is added / deleted.

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