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ジャンルのカテゴリ―名

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<p data-bm="27" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: 4px; padding: revert; -webkit-line-clamp: revert; color: rgba(0, 0, 0, 0.8); font-family: Roboto, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;" data-pasted="true">ASP.NET Core 10.0 MVC（.NET 8ベース）で&nbsp;親（Category） と&nbsp;子（SubCategory） の1対多リレーションを想定した&nbsp;Models クラス の完全なコード例を示します。 Entity Framework Core を使い、ナビゲーションプロパティ と&nbsp;データアノテーション を適切に設定します。<h2 data-bm="28" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: revert; padding: revert; font: 22px / 24px Roboto, Helvetica, sans-serif; height: 32px; -webkit-line-clamp: 1; overflow: hidden; text-overflow: ellipsis; display: -webkit-box; -webkit-box-orient: vertical; color: rgba(0, 0, 0, 0.8); letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Models/Category.cs</h2><pre data-priority="2" data-bm="29" style="background: none 0% 0% / auto repeat scroll padding-box border-box rgb(245, 245, 245); border: 1px solid rgba(0, 0, 0, 0.1); border-radius: 8px; overflow: hidden; color: rgba(0, 0, 0, 0.8); font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><div data-bm="37" style="display: flex; height: 28px; flex-direction: row; justify-content: space-between; align-items: center; gap: 8px; padding: 8px 12px; border-bottom: 1px solid rgba(0, 0, 0, 0.1); background: none 0% 0% / auto repeat scroll padding-box border-box rgb(248, 244, 241);"><h5 style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: 0px; padding: revert; font-style: normal !important; font-variant: normal !important; font-weight: 400 !important; font-stretch: 100% !important; line-height: 18px; font-family: Roboto, Helvetica, sans-serif !important; font-optical-sizing: auto !important; font-size-adjust: none !important; font-kerning: auto !important; font-feature-settings: normal !important; font-variation-settings: normal !important; font-language-override: normal !important; font-size: 16px; display: inline-block; color: rgb(60, 81, 180);">Csharp</h5><div style="height: 28px;"><button type="button" tabindex="" title="Copy code" style="box-sizing: border-box; margin: 0px; padding: 0px; font: 400 13px / 20px Roboto, Helvetica, sans-serif; background-color: rgb(217, 223, 251); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(60, 81, 180) !important; text-decoration: none !important; border-radius: 9999px; block-size: 28px; gap: 2px; padding-inline: 10px;"><div style="box-sizing: border-box; margin: 0px; padding: 0px; min-inline-size: 0px; max-inline-size: 100%; white-space: nowrap; text-overflow: ellipsis; overflow: clip; max-block-size: calc(1lh); padding-inline: 2px;">Copy code</div></button></div></div><code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255); display: block; white-space: pre-wrap; overflow-wrap: anywhere; padding: 8px 16px 16px;">using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;

namespace YourApp.Models
{
 /// &lt;summary&gt;
 /// 親カテゴリモデル
 /// &lt;/summary&gt;
 public class Category
 {
 [Key] // 主キー
 public int CategoryId { get; set; }

 [Required(ErrorMessage = &quot;カテゴリ名は必須です。&quot;)]
 [StringLength(100, ErrorMessage = &quot;カテゴリ名は100文字以内で入力してください。&quot;)]
 public string Name { get; set; } = string.Empty;

 // 子カテゴリとの1対多リレーション
 public ICollection&lt;SubCategory&gt; SubCategories { get; set; } = new List&lt;SubCategory&gt;();
 }
}
</code></pre><h2 data-bm="30" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: revert; padding: revert; font: 22px / 24px Roboto, Helvetica, sans-serif; height: 32px; -webkit-line-clamp: 1; overflow: hidden; text-overflow: ellipsis; display: -webkit-box; -webkit-box-orient: vertical; color: rgba(0, 0, 0, 0.8); letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Models/SubCategory.cs</h2><pre data-priority="2" data-bm="31" style="background: none 0% 0% / auto repeat scroll padding-box border-box rgb(245, 245, 245); border: 1px solid rgba(0, 0, 0, 0.1); border-radius: 8px; overflow: hidden; color: rgba(0, 0, 0, 0.8); font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><div data-bm="38" style="display: flex; height: 28px; flex-direction: row; justify-content: space-between; align-items: center; gap: 8px; padding: 8px 12px; border-bottom: 1px solid rgba(0, 0, 0, 0.1); background: none 0% 0% / auto repeat scroll padding-box border-box rgb(248, 244, 241);"><h5 style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: 0px; padding: revert; font-style: normal !important; font-variant: normal !important; font-weight: 400 !important; font-stretch: 100% !important; line-height: 18px; font-family: Roboto, Helvetica, sans-serif !important; font-optical-sizing: auto !important; font-size-adjust: none !important; font-kerning: auto !important; font-feature-settings: normal !important; font-variation-settings: normal !important; font-language-override: normal !important; font-size: 16px; display: inline-block; color: rgb(60, 81, 180);">Csharp</h5><div style="height: 28px;"><button type="button" tabindex="" title="Copy code" style="box-sizing: border-box; margin: 0px; padding: 0px; font: 400 13px / 20px Roboto, Helvetica, sans-serif; background-color: rgb(217, 223, 251); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(60, 81, 180) !important; text-decoration: none !important; border-radius: 9999px; block-size: 28px; gap: 2px; padding-inline: 10px;"><div style="box-sizing: border-box; margin: 0px; padding: 0px; min-inline-size: 0px; max-inline-size: 100%; white-space: nowrap; text-overflow: ellipsis; overflow: clip; max-block-size: calc(1lh); padding-inline: 2px;">Copy code</div></button></div></div><code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255); display: block; white-space: pre-wrap; overflow-wrap: anywhere; padding: 8px 16px 16px;">using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace YourApp.Models
{
 /// &lt;summary&gt;
 /// 子カテゴリモデル
 /// &lt;/summary&gt;
 public class SubCategory
 {
 [Key] // 主キー
 public int SubCategoryId { get; set; }

 [Required(ErrorMessage = &quot;サブカテゴリ名は必須です。&quot;)]
 [StringLength(100, ErrorMessage = &quot;サブカテゴリ名は100文字以内で入力してください。&quot;)]
 public string Name { get; set; } = string.Empty;

 // 外部キー
 [ForeignKey(nameof(Category))]
 public int CategoryId { get; set; }

 // 親カテゴリへのナビゲーションプロパティ
 public Category? Category { get; set; }
 }
}
</code></pre><h2 data-bm="32" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: revert; padding: revert; font: 22px / 24px Roboto, Helvetica, sans-serif; height: 32px; -webkit-line-clamp: 1; overflow: hidden; text-overflow: ellipsis; display: -webkit-box; -webkit-box-orient: vertical; color: rgba(0, 0, 0, 0.8); letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">DbContext 設定例（Data/ApplicationDbContext.cs）</h2><pre data-priority="2" data-bm="33" style="background: none 0% 0% / auto repeat scroll padding-box border-box rgb(245, 245, 245); border: 1px solid rgba(0, 0, 0, 0.1); border-radius: 8px; overflow: hidden; color: rgba(0, 0, 0, 0.8); font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><div data-bm="39" style="display: flex; height: 28px; flex-direction: row; justify-content: space-between; align-items: center; gap: 8px; padding: 8px 12px; border-bottom: 1px solid rgba(0, 0, 0, 0.1); background: none 0% 0% / auto repeat scroll padding-box border-box rgb(248, 244, 241);"><h5 style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: 0px; padding: revert; font-style: normal !important; font-variant: normal !important; font-weight: 400 !important; font-stretch: 100% !important; line-height: 18px; font-family: Roboto, Helvetica, sans-serif !important; font-optical-sizing: auto !important; font-size-adjust: none !important; font-kerning: auto !important; font-feature-settings: normal !important; font-variation-settings: normal !important; font-language-override: normal !important; font-size: 16px; display: inline-block; color: rgb(60, 81, 180);">Csharp</h5><div style="height: 28px;"><button type="button" tabindex="" title="Copy code" style="box-sizing: border-box; margin: 0px; padding: 0px; font: 400 13px / 20px Roboto, Helvetica, sans-serif; background-color: rgb(217, 223, 251); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(60, 81, 180) !important; text-decoration: none !important; border-radius: 9999px; block-size: 28px; gap: 2px; padding-inline: 10px;"><div style="box-sizing: border-box; margin: 0px; padding: 0px; min-inline-size: 0px; max-inline-size: 100%; white-space: nowrap; text-overflow: ellipsis; overflow: clip; max-block-size: calc(1lh); padding-inline: 2px;">Copy code</div></button></div></div><code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255); display: block; white-space: pre-wrap; overflow-wrap: anywhere; padding: 8px 16px 16px;">using Microsoft.EntityFrameworkCore;
using YourApp.Models;

namespace YourApp.Data
{
 public class ApplicationDbContext : DbContext
 {
 public ApplicationDbContext(DbContextOptions&lt;ApplicationDbContext&gt; options)
 : base(options)
 {
 }

 public DbSet&lt;Category&gt; Categories { get; set; }
 public DbSet&lt;SubCategory&gt; SubCategories { get; set; }

 protected override void OnModelCreating(ModelBuilder modelBuilder)
 {
 base.OnModelCreating(modelBuilder);

 // Category - SubCategory の1対多リレーション設定
 modelBuilder.Entity&lt;Category&gt;()
 .HasMany(c =&gt; c.SubCategories)
 .WithOne(sc =&gt; sc.Category)
 .HasForeignKey(sc =&gt; sc.CategoryId)
 .OnDelete(DeleteBehavior.Cascade); // 親削除時に子も削除
 }
 }
}
</code></pre><h2 data-bm="34" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: revert; padding: revert; font: 22px / 24px Roboto, Helvetica, sans-serif; height: 32px; -webkit-line-clamp: 1; overflow: hidden; text-overflow: ellipsis; display: -webkit-box; -webkit-box-orient: vertical; color: rgba(0, 0, 0, 0.8); letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">補足</h2><ul data-bm="35" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: revert; padding: revert; color: rgba(0, 0, 0, 0.8); font-family: Roboto, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><li style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin-top: revert; margin-right: revert; margin-bottom: 8px; margin-left: revert; padding: revert;">Category と&nbsp;SubCategory は&nbsp;1対多 の関係です。</li><li style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin-top: revert; margin-right: revert; margin-bottom: 8px; margin-left: revert; padding: revert;"><code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255);">OnDelete(DeleteBehavior.Cascade)</code> により、親削除時に子も自動削除されます。</li><li style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin-top: revert; margin-right: revert; margin-bottom: 8px; margin-left: revert; padding: revert;"><code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255);">DataAnnotations</code> によるバリデーションを追加して、MVC のフォーム入力時に検証可能にしています。</li><li style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin-top: revert; margin-right: revert; margin-bottom: 8px; margin-left: revert; padding: revert;">このまま&nbsp;<code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255);">dotnet ef migrations add InitialCreate</code> &rarr;&nbsp;<code style="border-radius: 8px; background: none 0% 0% / auto repeat scroll padding-box border-box rgb(255, 255, 255);">dotnet ef database update</code> でテーブルが作成されます。</li></ul><p data-bm="36" style="border: 0px; border-collapse: collapse; border-spacing: 0px; list-style-position: initial; list-style-image: initial; list-style-type: revert; margin: 4px; padding: revert; -webkit-line-clamp: revert; color: rgba(0, 0, 0, 0.8); font-family: Roboto, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">もしご希望であれば、このモデルを使った&nbsp;CRUD コントローラーとビューのサンプル も作成できます。 次にそれを作れば、すぐに動く ASP.NET Core MVC アプリになりますが、作成しますか？Powered by <a href="https://www.froala.com/wysiwyg-editor?pb=1" title="Froala Editor">Froala Editor</a>

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