c# - 根据三个不同的字段返回非不同的对象

Question

鉴于以下情况，我希望能够根据两个字段提取非不同的值：名称和国家/地区。在这个例子中，我想返回列表中的前两个。

List<City> cities = new List<City>
{
new City{ Name = "Sydney", Country = "Australia", Galaxy = "Mine"  },
new City{ Name = "Sydney", Country = "Australia", Galaxy = "Yours" },
new City{ Name = "New York", Country = "USA", Galaxy = "Ours"},
new City{ Name = "Paris", Country = "France", Galaxy = "Theirs" },

};

Answer 1

此查询将按名称和国家/地区返回不明确的城市（即在您的情况下为前两个）：

IEnumerable<City> query = 
    cities.GroupBy(c => new { c.Name, c.Country })
          .Where(g => g.Count() > 1)
          .SelectMany(g => g);