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:

我试图用通货膨胀率除以 GDP...然后按升序排序，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;

我得到了输出:

12
6
4
3
2
2

无论我在查询中使用升序还是降序。我怎样才能让数据升序？即

2
2
3
4
6
12

Answer 1

MSDN orderby clause

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

---

我不能只用数组重现:

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 的缺陷。 (我无法对此进行测试。)

如果是这种情况，您可以强制求值(通过下面的 .ToArray())然后对其进行排序。作为使用 LINQ 的任何静态数据的使用者，我期望 ToArray 调用是不必要的。

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));