c# - linq "let" 除法，然后按升序排序

Question

我有这些数据，我正在使用 linqToExcel：

我试图将通货膨胀除以 GDP ......然后让它们升值，但我做错了。

    var people = from x in excel.Worksheet<CountryEconomics>("Sheet1")
                 let c = x.Inflation / x.GDP
                 orderby c ascending 
                 select c;

我得到输出：

12
6
4
3
2
2

无论我在查询中放置升序还是降序。我怎样才能让数据升序？IE

2
2
3
4
6
12

Answer 1

MSDN orderby 子句

var people = from x in excel.Worksheet<CountryEconomics>("Sheet1")
             let c = x.Inflation / x.GDP
             orderby c
             select c;  

---

我不能只用一个数组来重现：

var economics = new[]
    {
        new {Country = "USA", GDP = 1, Inflation = 12},
        new {Country = "GB", GDP = 2, Inflation = 12},
        new {Country = "JPN", GDP = 3, Inflation = 12},
        new {Country = "GER", GDP = 4, Inflation = 12},
        new {Country = "CHI", GDP = 5, Inflation = 12},
        new {Country = "CAN", GDP = 6, Inflation = 12},
    };

var people = from x in economics
             let c = x.Inflation/x.GDP
             orderby c
             select c;

// without "orderby c":  12, 6, 4, 3, 2, 2
// with "orderby c":  2, 2, 3, 4, 6, 12
Console.WriteLine(string.Join(", ", people));

---

这可能是 Linq-to-Excel 的一个缺陷。（我无法对此进行测试。）

如果是这种情况，您可以强制评估（通过.ToArray()下面），然后对其进行排序。作为使用 LINQ 的任何静态数据的使用者，我希望调用ToArray是不必要的。

var people = from x in economics
             let c = x.Inflation/x.GDP
             select c;

var sorted = people.ToArray().OrderBy(c => c);
Console.WriteLine(string.Join(", ", sorted));

Answer 2

如果您只想按 排序Inflation / GDP，您可以这样做：

var people = from x in excel.Worksheet<CountryEconomics>("Sheet1")
             orderby x.Inflation / x.GDP
             select x;

或流利的语法：

var people = excel.Worksheet<CountryEconomics>("Sheet1")
                  .OrderBy(x => x.Inflation / x.GDP);

我不确定，但您可能需要跳过第一行（有标题）。

var people = excel.Worksheet<CountryEconomics>("Sheet1")
                  .Skip(1).OrderBy(x => x.Inflation / x.GDP);

Answer 3

现在，我只是在猜测，但也许添加一些演员表可以使它起作用：

var people = from x in excel.Worksheet<CountryEconomics>("Sheet1")
             let c = ((double)x.Inflation) / ((double)x.GDP)
             orderby c ascending 
             select c;

但是，如果这也失败了 - 如果您先将其列为列表会发生什么：

var people = from x in excel.Worksheet<CountryEconomics>("Sheet1").ToList()
             let c = ((double)x.Inflation) / ((double)x.GDP)
             orderby c ascending
             select c;

如果仍然失败：

var people = from x in excel.Worksheet<CountryEconomics>("Sheet1")
             let c = ((double)x.Inflation) / ((double)x.GDP)
             select c;

var peopleList = people.ToList().OrderBy(p => p);

希望这能完成...