C#使用組選擇重復項-有解無憂

我只想從任何組多次包含相同 ID 的非空白名稱中選擇：

資料設定

var a1 = new { id = 3, Name = "", Group = "GroupA" };
var a2 = new { id = 2, Name = "", Group = "GroupA" };
var a3 = new { id = 3, Name = "", Group = "GroupA" };
var b1 = new { id = 4, Name = "B", Group = "GroupB" };
var b2 = new { id = 5, Name = "B", Group = "GroupB" };
var b3 = new { id = 5, Name = "B", Group = "GroupB" };
List<dynamic> group = new List<dynamic>();
group.Add(a1);
group.Add(a2);
group.Add(a3);
group.Add(b1);
group.Add(b2);
group.Add(b3);

詢問：

var query1 = group.ToList()
    .Where(s=>s.Name != "")
    .GroupBy(x =>x.Group)
    .Where(g => g.Count() > 1)
    .SelectMany(y => y)
    .ToList();
Console.WriteLine("output\n"   string.Join("\n", query1));

退貨

 id = 4, Name = B, Group = GroupB 
 id = 5, Name = B, Group = GroupB 
 id = 5, Name = B, Group = GroupB

但我想要的是以下內容：

 id = 5, Name = B, Group = GroupB 
 id = 5, Name = B, Group = GroupB

我究竟做錯了什么？

uj5u.com熱心網友回復：

按id和/或Name根據您的需要分組

.GroupBy(x => new {x.id, x.Name})

給定的

var list = new[]
{
   new {id = 3, Name = "", Group = "GroupA"},
   new {id = 2, Name = "", Group = "GroupA"},
   new {id = 3, Name = "", Group = "GroupA"},
   new {id = 4, Name = "B", Group = "GroupB"},
   new {id = 5, Name = "B", Group = "GroupB"},
   new {id = 5, Name = "B", Group = "GroupB"}
};

用法

var results = list
   .Where(s => s.Name != "")
   .GroupBy(x => new {x.id, x.Name})
// .GroupBy(x => x.id) <- depending on your needs
   .Where(g => g.Count() > 1)
   .SelectMany(y => y);

foreach (var result in results)
   Console.WriteLine($"{result.id}, {result.Name}, {result.Group}");

輸出

5, B, GroupB
5, B, GroupB

uj5u.com熱心網友回復：

你申請GroupBy到Group財產。而不是按Group財產分組，使用id財產，

輸入

var list = new[]
{
    new {id = 3, Name = "", Group = "GroupA"},
    new {id = 2, Name = "", Group = "GroupA"},
    new {id = 3, Name = "", Group = "GroupA"},
    new {id = 4, Name = "B", Group = "GroupB"},
    new {id = 5, Name = "B", Group = "GroupB"},
    new {id = 5, Name = "B", Group = "GroupB"}
};

解決方案：

var query1 = list.ToList()
    .Where(s=>s.Name != "")
    .GroupBy(x =>x.id)  
               //^^^^^ This change you need to do  
    .Where(g => g.Count() > 1)
    .SelectMany(y => y)
    .ToList();

輸出

5, B, GroupB
5, B, GroupB

網上試試

轉載請註明出處，本文鏈接：https://www.uj5u.com/shujuku/340919.html

標籤：C＃林克拉姆达

上一篇：List的擴展方法來計算WhereNot

下一篇：在C#中對字典串列進行分組