Question

我感觉这里发生了一些愚蠢的语法错误，但是我一生都无法解决。我正在尝试使用多个属性对一个大列表进行排序。

方法A：

IOrderedEnumerable<myClass> orderedList = myList.OrderByDescending(e => e.Tier);

orderedList = orderedList.ThenByDescending(e => e.Priority[0].Value);
orderedList = orderedList.ThenByDescending(e => e.Priority[1].Value);
orderedList = orderedList.ThenByDescending(e => e.Priority[2].Value);

orderedList = orderedList.ThenByDescending(e => e.Score);

方法B：

IOrderedEnumerable<myClass> orderedList = myList.OrderByDescending(e => e.Tier);

for (int i = 0; i < 3; i++)
{
    orderedList = orderedList.ThenByDescending(e => e.Priority[i].Value);
}

orderedList = orderedList.ThenByDescending(e => e.Score);

上述方法A可以完美地工作，但是方法B（我需要这样做）仍然返回超出范围错误的索引，即使它应该完全相同（即0、1、2）

在两种情况下，e.Priority代表3个KeyValuePair的列表。我不明白为什么方法B会返回超出范围的错误。

Answer 1

嘿，这里有经典的循环问题。正确的方法：

IOrderedEnumerable<myClass> orderedList = myList.OrderByDescending(e => e.Tier);

for (int i = 0; i < 3; i++)
{
    int capturedIndex = i;
    orderedList = orderedList.ThenByDescending(e => e.Priority[capturedIndex].Value);
}

orderedList = orderedList.ThenByDescending(e => e.Score);

更多内容：Captured variable in a loop in C#

在循环内执行LINQ的ThenBy有麻烦

1 个答案: