仅从对象中选择元素出现一次的那些值

Question

我只需要从List对象中选择那些段名只有一次的项目，例如在附加的图像中，只返回具有SegmentName =＆＃34; C＆＃34;的元素;因为在列表中只有一次...

这是我到目前为止尝试的示例代码。

var empty = count
  .Where(x => x.Count > 1 & x.SegmentName.Count() == 1)
  .Select(k => new { 
     SegName = k.SegmentName, 
     Value = k.FieldValue, 
     No = k.Count })
  .ToList();

样品：

Answer 1

这可能会为你做到这一点

elements.GroupBy(x => x).Where(y => y.Count() <= 1).Select(z => z.Key).ToList();

这将返回仅存在一次的所有元素的列表

示例

List<string> SegmentName = new List<string>();
SegmentName.Add("A");
SegmentName.Add("A");
SegmentName.Add("B");
SegmentName.Add("B");
SegmentName.Add("C");
List<string> newlist = SegmentName.GroupBy(x => x).Where(g => g.Count() <= 1).Select(y => y.Key).ToList();

输出

  

＆＃34; C＆＃34;

因此，对于您的自定义对象，它应该是

count.GroupBy(x => x.SegmentName)
     .Where(y=> y.Count()<=1)
     .Select(k => new {
                        SegName = k.SegmentName, 
                        Value = k.FieldValue, 
                        Count = k.Count 
                      })
     .ToList()

Answer 2

希望您正在寻找类似的东西：

array[i][j]

Answer 3

给GroupBy一个

var empty = count.GroupBy(x => x.SegmentName)
  .Select(x => x.First())
  .ToList();

Answer 4

这可能对你有帮助，看看这个

http://www.dotnettricks.com/learn/linq/sql-joins-with-csharp-linq

Answer 5

var count = new [] { 
    new { SegmentName = "A", FieldValue = "", Count = 2 }, 
    new { SegmentName = "A", FieldValue = "ABC", Count = 1 },
    new { SegmentName = "B", FieldValue = "", Count = 2 },
    new { SegmentName = "B", FieldValue = "ABC", Count = 1 },
    new { SegmentName = "C", FieldValue = "", Count = 3 },
};

var result = count
    .GroupBy(x => x.SegmentName)
    .Where(y => y.Count() == 1)
    .Select(z => z.First()) // Need to implicitly get the first item here
    .ToList();

foreach(var item in result)
{
    Console.WriteLine("SegmentName={0} FieldValue={1} Count={2}", item.SegmentName, item.FieldValue, item.Count);
}