C#の概念 LINQ（null）

　nullの条件分岐とキャスト。

成果物

• github

情報源

• https://docs.microsoft.com/ja-jp/dotnet/csharp/linq/handle-null-values-in-query-expressions

コード

null除外

from c in categories
where c != null
join p in products on c.ID equals p?.CategoryID
select new { Category = c.Name, Name = p.Name };

null許容型へキャスト

from c in categories
join p in products on c.ID equals (int?)p.CategoryID
select new { Category = c.Name, Name = p.Name };

対象環境

• 2019-12-12
• Raspbierry pi 3 Model B+
• Raspbian stretch 9.0 2018-11-13
• bash 5.0.3(1)-release

$ uname -a
Linux raspberrypi 4.19.75-v7l+ #1270 SMP Tue Sep 24 18:51:41 BST 2019 armv7l GNU/Linux