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トップLINQに関する質問C# LINQでJOINをした結果をWHERE句で抽出レコードを限定する方法

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3

言語指定の誤りを修正

2022/08/16 13:37

投稿

jhashimoto
jhashimoto

スコア838

test CHANGED
@@ -1,141 +1,71 @@
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1
  こんな感じでどうでしょうか。
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-
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-
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- ```lang-c#
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+ ```c#
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-
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  using System;
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-
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  using System.Linq;
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-
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-
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  namespace LinqSample {
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  class Program {
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  static void Main(string[] args) {
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  var traders = new Trader[] {
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  new Trader() { Id = 1, CompanyNm = "株式会社ABC", Address = "北海道" },
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  new Trader() { Id = 2, CompanyNm = "株式会社DEF", Address = "青森" },
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  new Trader() { Id = 3, CompanyNm = "株式会社GHI", Address = "秋田" },
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  new Trader() { Id = 4, CompanyNm = "株式会社HIJ", Address = "岩手" },
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  new Trader() { Id = 5, CompanyNm = "株式会社KLM", Address = "山形" },
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  new Trader() { Id = 6, CompanyNm = "株式会社OPQ", Address = "宮城" },
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  };
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  var items = new ItemList[] {
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  new ItemList() { Id = 1, Price = 100, ExpiryDate = new DateTime(2000, 4, 1) },
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  new ItemList() { Id = 2, Price = 200, ExpiryDate = new DateTime(2005, 5, 1) },
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  new ItemList() { Id = 3, Price = 300, ExpiryDate = new DateTime(2010, 6, 1) },
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  new ItemList() { Id = 4, Price = 400, ExpiryDate = new DateTime(2015, 7, 1) },
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  new ItemList() { Id = 5, Price = 2020, ExpiryDate = new DateTime(2020, 8, 1) }
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  };
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  var result = traders.GroupJoin(
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  items,
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  trader => trader.Id,
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  item => item.Id,
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  (trader, item) => new { trader, item })
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  // シーケンスの展開
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  .SelectMany(traderAndItem => traderAndItem.item, (trader, item) => new {
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  Id = trader.trader.Id,
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  CompanyNm = trader.trader.CompanyNm,
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  Address = trader.trader.Address,
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  Price = item.Price,
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  ExpireDate = item.ExpiryDate
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  })
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  .Where(o => o.ExpireDate > new DateTime(2010, 1, 1))
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  .ToList();
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  foreach (var o in result) {
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  Console.WriteLine($"Id={o.Id}, CompanyNm={o.CompanyNm}, Address={o.Address}, Price={o.Price}, ExpireDate={o.ExpireDate}");
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  }
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  }
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  }
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  class Trader {
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  public int Id { get; set; }
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  public string CompanyNm { get; set; }
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  public string Address { get; set; }
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  }
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-
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-
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  class ItemList {
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  public int Id { get; set; }
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  public int Price { get; set; }
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  public DateTime ExpiryDate { get; set; }
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  }
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-
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  }
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  ```
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  出力。
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  ```
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  Id=3, CompanyNm=株式会社GHI, Address=秋田, Price=300, ExpireDate=10/06/01 0:00:00
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-
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  Id=4, CompanyNm=株式会社HIJ, Address=岩手, Price=400, ExpireDate=15/07/01 0:00:00
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  Id=5, CompanyNm=株式会社KLM, Address=山形, Price=2020, ExpireDate=20/08/01 0:00:00
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-
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  ```

2

refactor

2021/10/24 03:19

投稿

jhashimoto
jhashimoto

スコア838

test CHANGED
@@ -16,7 +16,7 @@
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17
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  static void Main(string[] args) {
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18
 
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- Trader[] traders = new Trader[] {
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+ var traders = new Trader[] {
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  new Trader() { Id = 1, CompanyNm = "株式会社ABC", Address = "北海道" },
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@@ -34,7 +34,7 @@
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35
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36
36
 
37
- ItemList[] items = new ItemList[] {
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+ var items = new ItemList[] {
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  new ItemList() { Id = 1, Price = 100, ExpiryDate = new DateTime(2000, 4, 1) },
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@@ -62,17 +62,17 @@
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  // シーケンスの展開
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64
 
65
- .SelectMany(o => o.item, (o, p) => new {
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+ .SelectMany(traderAndItem => traderAndItem.item, (trader, item) => new {
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66
 
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- Id = o.trader.Id,
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+ Id = trader.trader.Id,
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- CompanyNm = o.trader.CompanyNm,
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+ CompanyNm = trader.trader.CompanyNm,
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- Address = o.trader.Address,
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+ Address = trader.trader.Address,
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- Price = p.Price,
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+ Price = item.Price,
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- ExpireDate = p.ExpiryDate
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+ ExpireDate = item.ExpiryDate
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  })
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78
 
@@ -118,6 +118,10 @@
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  }
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+
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+
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+
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+
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  ```
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1

ToListを追加

2021/10/24 03:19

投稿

jhashimoto
jhashimoto

スコア838

test CHANGED
@@ -76,7 +76,9 @@
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  })
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- .Where(o => o.ExpireDate > new DateTime(2010, 1, 1));
79
+ .Where(o => o.ExpireDate > new DateTime(2010, 1, 1))
80
+
81
+ .ToList();
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82
84
 
@@ -116,8 +118,6 @@
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  }
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-
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  ```
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