从列表不区分大小写中获取重复项

Question

List<string> testList = new List<string>();
testList.Add("A");
testList.Add("A");
testList.Add("C");
testList.Add("d");
testList.Add("D");

此查询区分大小写:

// Result: "A"
List<String> duplicates = testList.GroupBy(x => x)
                                  .Where(g => g.Count() > 1)
                                  .Select(g => g.Key)
                                  .ToList();

它如何看起来不区分大小写？(结果:"A","d")

Answer 1

通过使用重载实现的GroupBy,你可以提供所需的比较器,如StringComparer.OrdinalIgnoreCase:

  var result = testList
    .GroupBy(item => item, StringComparer.OrdinalIgnoreCase)
    .Where(g => g.Count() > 1)
    .Select(g => g.Key)
    .ToList();