我想過濾掉 "" 名稱，然后選擇每個有重復 ID 的唯一位置，而不管名稱如何：
資料設定
var list = new[]
{
new { id = 3, Name = "", Location = "LocationA" },
new { id = 2, Name = "", Location = "LocationA" },
new { id = 1, Name = "T", Location = "LocationB" },
new { id = 2, Name = "H", Location = "LocationB" },
new { id = 3, Name = "E", Location = "LocationB" },
new { id = 3, Name = "R", Location = "LocationB" },
new { id = 5, Name = "U", Location = "LocationC" },
new { id = 5, Name = "S", Location = "LocationC" },
new { id = 5, Name = "S", Location = "LocationD" },
new { id = 4, Name = "O", Location = "LocationD" },
new { id = 4, Name = "Z", Location = "LocationE" },
};
詢問
var query1 = list
.Where(s => s.Name != "")
.GroupBy(g => g.Location)
.Where(w => w.Select(s => s.Location).Count() > 1)
.SelectMany(s => s)
.GroupBy(g => g.id)
.Where(w => w.Select(s => s.id).Count() > 1)
.SelectMany(s => s)
.ToList();
Console.WriteLine("output\n" string.Join("\n", query1));
退貨
{ id = 3, Name = E, Location = LocationB }
{ id = 3, Name = R, Location = LocationB }
{ id = 5, Name = U, Location = LocationC }
{ id = 5, Name = S, Location = LocationC }
{ id = 5, Name = S, Location = LocationD }
vs我真正想要的
{ id = 3, Name = E, Location = LocationB }
{ id = 3, Name = R, Location = LocationB }
{ id = 5, Name = U, Location = LocationC }
{ id = 5, Name = S, Location = LocationC }
LocationD 的 ID 為 4 和 5，因此應該將其過濾掉，但我無法這樣做。我究竟做錯了什么？我該如何糾正？
uj5u.com熱心網友回復：
給定的
var list = new[]
{
new { id = 3, Name = "", Location = "LocationA" },
new { id = 2, Name = "", Location = "LocationA" },
new { id = 1, Name = "T", Location = "LocationB" },
new { id = 2, Name = "H", Location = "LocationB" },
new { id = 3, Name = "E", Location = "LocationB" },
new { id = 3, Name = "R", Location = "LocationB" },
new { id = 5, Name = "U", Location = "LocationC" },
new { id = 5, Name = "S", Location = "LocationC" },
new { id = 5, Name = "S", Location = "LocationD" },
new { id = 4, Name = "O", Location = "LocationD" },
new { id = 4, Name = "Z", Location = "LocationE" },
};
例子
var results = list
.Where(s => s.Name != "")
.GroupBy(x => new {x.id, x.Location})
.Where(g => g.Count() > 1)
.SelectMany(y => y);
foreach (var result in results)
Console.WriteLine($"{result.id}, {result.Name}, {result.Location}");
輸出
3, E, LocationB
3, R, LocationB
5, U, LocationC
5, S, LocationC
uj5u.com熱心網友回復：
按id和分組Location。并獲得.Count()超過 1 個。
var query1 = list
.Where(s => s.Name != "")
.GroupBy(g => new { g.Location, g.id })
.Where(g => g.Count() > 1)
.SelectMany(g => g)
.ToList();
示例演示
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