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Linq GroupBy并获取不为null的条目

linq c#

-3

Revious · 技术社区 · 6 年前

public class Selection
{
    string IdSelectionType {get; set;}
    string Name {get; set;}
    decimal? OddValue {get; set;}
    bool Visible {get; set;}
}

示例数据

var originalList = new List<Selection>()
        {
            new Selection() {IdSelectionType = "1", Name = "Under (75.50)", Visible = true},
            new Selection() {IdSelectionType = "2", Name = "Under (75.50)", Visible = true},
            new Selection() {IdSelectionType = "1", Name = "Under (75.50)", OddValue = 1.840m, Visible = true},
            new Selection() {IdSelectionType = "2", Name = "Under (75.50)", OddValue = 1.860m, Visible = true},
        };

有没有Linq/MoreLinq操作符可以做类似的事情?

Selections.GroupBy(s =>
          new {s.IdSelectionType, s.Name, s.OddValue, s.Visible})
          .Select(g => g.First()).ToList();

预期结果将是:

2 回复 | 直到 6 年前

Revious 6 年前

var result = items.OrderBy(x => x.Name)
                  .ThenByDescending(x => x.OddValue)
                  .GroupBy(s => new {s.IdSelectionType, s.Name, s.Visible})
                  .Select(x => x.FirstOrDefault())
                  .ToList();

Name 和 OddValue 然后分组 . 您将有与 OddValue != null 在输入之前 OddValue == null . 然后取每个分组的第一个条目。

OddValue==null 没有其他条目与此相同 姓名

最终结果: https://dotnetfiddle.net/jZ5gs2

Revious 6 年前

你可以用工会。选择所有没有OddValue==null的元素,然后将剩余的元素(具有null的元素)与第一个列表合并。

https://linqsamples.com/linq-to-objects/set/Union

var originalList = new[]
        {
            new Selection() {IdSelectionType = "1", Name = "Under (75.50)", Visible = true},
            new Selection() {IdSelectionType = "2", Name = "Under (75.50)", Visible = true},
            //new Selection() {IdSelectionType = "1", Name = "Under (75.50)", OddValue = 1.840m, Visible = true},
            new Selection() {IdSelectionType = "2", Name = "Under (75.50)", OddValue = 1.860m, Visible = true},
        };

        var noneNulls = originalList.Where(ol => ol.OddValue != null);

        var endList = originalList
            .Where(ol => !noneNulls.Select(nn => nn.IdSelectionType).Contains(ol.IdSelectionType))
            .Union(noneNulls);

https://dotnetfiddle.net/UJ8FaS