c# - 通过任意排序表达式对列表进行排序？

Question

问题:

我有一个通用列表，如下所示:

System.Collections.Generic.List<Question> myquestions = new System.Collections.Generic.List<Question>();

我有一个分页示例，使用从数据库获取的 LINQ 表，执行此操作进行分页:

var questions = context.Questions
    .OrderBy(sidx + " " + sord)
    .Skip(pageIndex * pageSize)
    .Take(pageSize);

现在，为了分页我从代码列表中填充的内容，我有:

var questionss = myquestions
    .OrderBy(x => x.Id)
    .Skip(pageIndex * pageSize)
    .Take(pageSize);

我想要的是能够像上例中那样通过字符串对“myquestions”进行排序。这可能吗？

Answer 1

由于延迟执行，您可以在单独的语句中链接扩展方法，这意味着您可以根据条件添加不同的排序:

IOrderedQueryable<Question> sorted;
switch (sort) {
  case "Id":  sorted = myquestions.OrderBy(x => x.Id);
  case "Name": sorted = myquestions.OrderBy(x => x.Name);
  case "Size": sorted = myquestions.OrderBy(x => x.Size);
  case "Id Desc":  sorted = myquestions.OrderByDescending(x => x.Id);
  case "Name Desc": sorted = myquestions.OrderByDescending(x => x.Name);
  case "Size Desc": sorted = myquestions.OrderByDescending(x => x.Size);
  default: throw new NotImplementedException();
}
var questions = sorted.Skip(pageIndex * pageSize).Take(pageSize);

您甚至可以添加二次排序(或者任意数量，在第一次之后它们都是一样的):

IOrderedQueryable<Question> sorted;
switch (sort) {
  case "Id":  sorted = myquestions.OrderBy(x => x.Id);
  case "Name": sorted = myquestions.OrderBy(x => x.Name);
  case "Size": sorted = myquestions.OrderBy(x => x.Size);
  case "Id Desc":  sorted = myquestions.OrderByDescending(x => x.Id);
  case "Name Desc": sorted = myquestions.OrderByDescending(x => x.Name);
  case "Size Desc": sorted = myquestions.OrderByDescending(x => x.Size);
  default: throw new NotImplementedException();
}
switch (sort2) {
  case "Id":  sorted = sorted.ThenBy(x => x.Id);
  case "Name": sorted = sorted.ThenBy(x => x.Name);
  case "Size": sorted = sorted.ThenBy(x => x.Size);
  case "Id Desc":  sorted = sorted.ThenByDescending(x => x.Id);
  case "Name Desc": sorted = sorted.ThenByDescending(x => x.Name);
  case "Size Desc": sorted = sorted.ThenByDescending(x => x.Size);
}
var questions = sorted.Skip(pageIndex * pageSize).Take(pageSize);