Question

基本上我想要选择两个字符串列并将它们全部放入一个字符串数组中。现在我必须做两个选择并结合结果。这不是什么大不了的事，我觉得它看起来很尴尬。有关如何使用一个linq语句实现相同目标的任何建议？这是我正在使用的测试用例：

[TestFixture]
  public class test {

    public class Values {
      public string Present { get; set; }
      public string Previous { get; set; }
      public bool Flag { get; set; }
    }

    [Test]
    public void test1() {

      var list = new List<Values> {
        new Values { Present = "present1", Previous = "previous1", Flag = false },
        new Values { Present = "present2", Previous = "previous2", Flag = false },
        new Values { Present = "present3", Previous = "previous3", Flag = true },
        new Values { Present = "present4", Previous = "previous4", Flag = true }
      };


      var r1 = list.Where(c => c.Flag).Select(c => c.Present);
      var r2 = list.Where(c => c.Flag).Select(c => c.Previous);
      var combined = r1.Concat(r2);

      Assert.AreEqual(4, combined.Count());
    }
  }

Answer 1

使用SelectMany的替代解决方案（它保留重复项）：

var combined = list.Where(c => c.Flag)
                   .SelectMany(c => new[] { c.Present, c.Previous });
Assert.AreEqual(4, combined.Count());

Answer 2

列表中字符串的最终排序是否重要？如果没有，似乎这是实现这一目标的最明确方式：

var strings = new List<String>();
foreach (var value in list.Where(c => c.Flag))
{
    strings.Add(value.Present);
    strings.Add(value.Previous);
}

使用LINQ将select中两列的结果合并为一个数组？

2 个答案: