記事編集

日付

ジャンルのカテゴリ―名

タイトル

内容の要旨

<p data-bm="79" 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">了解です。<br>では、前回の多階層対応版をベースに、<strong style="font-weight: 700;">より実用的な改良</strong>を加えて再生成します。<br>今回は以下の点を改善します。</p><ul data-bm="80" 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;"><strong style="font-weight: 700;">ViewModel導入</strong>：DBエンティティを直接Viewに渡さず、表示用に整形</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;"><strong style="font-weight: 700;">選択状態保持</strong>：選択済みカテゴリを初期表示できる</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;"><strong style="font-weight: 700;">インデント記号を柔軟化</strong>：階層深度に応じて自動生成</li></ul><h2 data-bm="81" 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;">1. モデル（DBエンティティ）</h2><pre data-priority="2" data-bm="82" 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="100" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(106, 115, 125);">// Models/Category.cs</span>
<span style="color: rgb(215, 58, 73);">using</span> System.Collections.Generic;
<span style="color: rgb(215, 58, 73);">using</span> System.ComponentModel.DataAnnotations;

<span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">class</span> <span style="color: rgb(111, 66, 193);">Category</span>
{
    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(227, 98, 9);">int</span> Id { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }

    [<span style="color: rgb(0, 92, 197);">Required</span>]
    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(227, 98, 9);">string</span> Name { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }

    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(227, 98, 9);">int</span>? ParentId { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }

    <span style="color: rgb(215, 58, 73);">public</span> Category Parent { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }
    <span style="color: rgb(215, 58, 73);">public</span> ICollection&lt;Category&gt; Children { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; } = <span style="color: rgb(215, 58, 73);">new</span> List&lt;Category&gt;();
}
</code></pre><h2 data-bm="83" 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;">2. ViewModel（表示用）</h2><pre data-priority="2" data-bm="84" 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="101" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(106, 115, 125);">// ViewModels/CategoryOptionViewModel.cs</span>
<span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">class</span> <span style="color: rgb(111, 66, 193);">CategoryOptionViewModel</span>
{
    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(227, 98, 9);">int</span> Id { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }
    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(227, 98, 9);">string</span> DisplayName { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }
}
</code></pre><h2 data-bm="85" 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;">3. DbContext</h2><pre data-priority="2" data-bm="86" 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="102" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(106, 115, 125);">// Data/ApplicationDbContext.cs</span>
<span style="color: rgb(215, 58, 73);">using</span> Microsoft.EntityFrameworkCore;

<span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">class</span> <span style="color: rgb(111, 66, 193);">ApplicationDbContext</span> : <span style="color: rgb(111, 66, 193);">DbContext</span>
{
    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(111, 66, 193);">ApplicationDbContext</span>(DbContextOptions&lt;ApplicationDbContext&gt; options)
        : <span style="color: rgb(111, 66, 193);">base</span>(options) { }

    <span style="color: rgb(215, 58, 73);">public</span> DbSet&lt;Category&gt; Categories { <span style="color: rgb(215, 58, 73);">get</span>; <span style="color: rgb(215, 58, 73);">set</span>; }
}
</code></pre><h2 data-bm="87" 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;">4. サービス（階層構築＋ViewModel変換）</h2><pre data-priority="2" data-bm="88" 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="103" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(106, 115, 125);">// Services/CategoryService.cs</span>
<span style="color: rgb(215, 58, 73);">using</span> Microsoft.EntityFrameworkCore;
<span style="color: rgb(215, 58, 73);">using</span> System.Collections.Generic;
<span style="color: rgb(215, 58, 73);">using</span> System.Linq;
<span style="color: rgb(215, 58, 73);">using</span> System.Threading.Tasks;

<span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">class</span> <span style="color: rgb(111, 66, 193);">CategoryService</span>
{
    <span style="color: rgb(215, 58, 73);">private</span> <span style="color: rgb(215, 58, 73);">readonly</span> ApplicationDbContext _context;

    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(111, 66, 193);">CategoryService</span>(ApplicationDbContext context)
    {
        _context = context;
    }

    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">async</span> Task&lt;List&lt;CategoryOptionViewModel&gt;&gt; GetCategoryOptionsAsync()
    {
        <span style="color: rgb(215, 58, 73);">var</span> categories = <span style="color: rgb(215, 58, 73);">await</span> _context.Categories.ToListAsync();
        <span style="color: rgb(215, 58, 73);">var</span> hierarchy = BuildHierarchy(categories, <span style="color: rgb(0, 92, 197);">null</span>);
        <span style="color: rgb(215, 58, 73);">var</span> options = <span style="color: rgb(215, 58, 73);">new</span> List&lt;CategoryOptionViewModel&gt;();
        FlattenHierarchy(hierarchy, options, <span style="color: rgb(0, 92, 197);">0</span>);
        <span style="color: rgb(215, 58, 73);">return</span> options;
    }

    <span style="color: rgb(215, 58, 73);">private</span> List&lt;Category&gt; <span style="color: rgb(111, 66, 193);">BuildHierarchy</span>(List&lt;Category&gt; all, <span style="color: rgb(227, 98, 9);">int</span>? parentId)
    {
        <span style="color: rgb(215, 58, 73);">return</span> all
            .Where(c =&gt; c.ParentId == parentId)
            .Select(c =&gt; {
                c.Children = BuildHierarchy(all, c.Id);
                <span style="color: rgb(215, 58, 73);">return</span> c;
            })
            .ToList();
    }

    <span style="color: rgb(215, 58, 73);">private</span> <span style="color: rgb(215, 58, 73);">void</span> <span style="color: rgb(111, 66, 193);">FlattenHierarchy</span>(List&lt;Category&gt; categories, List&lt;CategoryOptionViewModel&gt; options, <span style="color: rgb(227, 98, 9);">int</span> depth)
    {
        <span style="color: rgb(215, 58, 73);">foreach</span> (<span style="color: rgb(215, 58, 73);">var</span> cat <span style="color: rgb(215, 58, 73);">in</span> categories)
        {
            options.Add(<span style="color: rgb(215, 58, 73);">new</span> CategoryOptionViewModel
            {
                Id = cat.Id,
                DisplayName = <span style="color: rgb(215, 58, 73);">new</span> <span style="color: rgb(227, 98, 9);">string</span>(<span style="color: rgb(3, 47, 98);">&#39;&mdash;&#39;</span>, depth * <span style="color: rgb(0, 92, 197);">2</span>) + cat.Name
            });

            <span style="color: rgb(215, 58, 73);">if</span> (cat.Children.Any())
            {
                FlattenHierarchy(cat.Children, options, depth + <span style="color: rgb(0, 92, 197);">1</span>);
            }
        }
    }
}
</code></pre><h2 data-bm="89" 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;">5. コントローラー</h2><pre data-priority="2" data-bm="90" 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="104" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(106, 115, 125);">// Controllers/MenuController.cs</span>
<span style="color: rgb(215, 58, 73);">using</span> Microsoft.AspNetCore.Mvc;
<span style="color: rgb(215, 58, 73);">using</span> System.Threading.Tasks;

<span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">class</span> <span style="color: rgb(111, 66, 193);">MenuController</span> : <span style="color: rgb(111, 66, 193);">Controller</span>
{
    <span style="color: rgb(215, 58, 73);">private</span> <span style="color: rgb(215, 58, 73);">readonly</span> CategoryService _categoryService;

    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(111, 66, 193);">MenuController</span>(CategoryService categoryService)
    {
        _categoryService = categoryService;
    }

    <span style="color: rgb(215, 58, 73);">public</span> <span style="color: rgb(215, 58, 73);">async</span> Task&lt;IActionResult&gt; <span style="color: rgb(111, 66, 193);">Index</span>(<span style="color: rgb(227, 98, 9);">int</span>? selectedId)
    {
        <span style="color: rgb(215, 58, 73);">var</span> options = <span style="color: rgb(215, 58, 73);">await</span> _categoryService.GetCategoryOptionsAsync();
        ViewBag.SelectedId = selectedId;
        <span style="color: rgb(215, 58, 73);">return</span> View(options);
    }
}
</code></pre><h2 data-bm="91" 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;">6. View（選択状態保持付き）</h2><pre data-priority="2" data-bm="92" 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="105" 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(243, 249, 254);"><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(11, 73, 127);">Html</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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;">@model List&lt;<span style="color: rgb(34, 134, 58);">CategoryOptionViewModel</span>&gt;
@{
    var selectedId = ViewBag.SelectedId as int?;
}

&lt;<span style="color: rgb(34, 134, 58);">select</span> <span style="color: rgb(0, 92, 197);">id</span>=<span style="color: rgb(3, 47, 98);">&quot;categoryDropdown&quot;</span> <span style="color: rgb(0, 92, 197);">class</span>=<span style="color: rgb(3, 47, 98);">&quot;form-select&quot;</span>&gt;
    &lt;<span style="color: rgb(34, 134, 58);">option</span> <span style="color: rgb(0, 92, 197);">value</span>=<span style="color: rgb(3, 47, 98);">&quot;&quot;</span>&gt;-- カテゴリを選択 --&lt;/<span style="color: rgb(34, 134, 58);">option</span>&gt;
    @foreach (var opt in Model)
    {
        &lt;<span style="color: rgb(34, 134, 58);">option</span> <span style="color: rgb(0, 92, 197);">value</span>=<span style="color: rgb(3, 47, 98);">&quot;@opt.Id&quot;</span> @(<span style="color: rgb(0, 92, 197);">selectedId</span> == <span style="color: rgb(3, 47, 98);">opt.Id</span> ? &quot;<span style="color: rgb(0, 92, 197);">selected</span>&quot; <span style="color: rgb(0, 92, 197);">:</span> &quot;&quot;)&gt;
            @opt.DisplayName
        &lt;/<span style="color: rgb(34, 134, 58);">option</span>&gt;
    }
&lt;/<span style="color: rgb(34, 134, 58);">select</span>&gt;
</code></pre><h2 data-bm="93" 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;">7. Program.cs</h2><pre data-priority="2" data-bm="94" 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="106" 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(243, 249, 254);"><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(11, 73, 127);">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(225, 240, 253); border: 1px solid rgba(0, 0, 0, 0); display: grid; grid-auto-flow: column; align-items: center; cursor: pointer; color: rgb(0, 0, 0) !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;"><span style="color: rgb(215, 58, 73);">using</span> Microsoft.EntityFrameworkCore;

<span style="color: rgb(215, 58, 73);">var</span> builder = WebApplication.CreateBuilder(args);

builder.Services.AddDbContext&lt;ApplicationDbContext&gt;(options =&gt;
    options.UseSqlServer(builder.Configuration.GetConnectionString(<span style="color: rgb(3, 47, 98);">&quot;DefaultConnection&quot;</span>)));

builder.Services.AddScoped&lt;CategoryService&gt;();
builder.Services.AddControllersWithViews();

<span style="color: rgb(215, 58, 73);">var</span> app = builder.Build();
app.MapDefaultControllerRoute();
app.Run();
</code></pre><h3 data-bm="95" 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; display: inline-block; font: 400 20px / 22px roboto, helvetica, sans-serif; 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;">改良点まとめ</h3><ol data-bm="96" 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;"><strong style="font-weight: 700;">ViewModel導入</strong><ul 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;"><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;">DB構造を直接Viewに渡さず、表示用に整形済みデータを渡すことで安全性と柔軟性向上。</li></ul></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;"><strong style="font-weight: 700;">選択状態保持</strong><ul 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;"><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);">selectedId</code>を渡せば、編集画面などで選択済み状態を再現可能。</li></ul></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;"><strong style="font-weight: 700;">インデント自動生成</strong><ul 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;"><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);">new string(&#39;&mdash;&#39;, depth * 2)</code>で階層深度に応じたインデントを自動付与。</li></ul></li></ol><p data-bm="97" 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;">この構成なら、<strong style="font-weight: 700;">多階層カテゴリのドロップダウン</strong>を安全かつ拡張性高く実装できます。<br>さらにUIを改善するなら、このデータを<strong style="font-weight: 700;">Ajax連動型</strong>にして動的ロードも可能です。</p><p data-bm="98" 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;">もし希望なら、このコードを<strong style="font-weight: 700;">Ajax連動型階層ドロップダウン</strong>に変換したバージョンも作成できます。<br>こちらは大規模データや動的フィルタリングに向いています。</p><p data-bm="99" 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;">作成しますか？<br>Ajax版なら、親選択時に子カテゴリだけを非同期取得できます。</p><p data-f-id="pbf" style="text-align: center; font-size: 14px; margin-top: 30px; opacity: 0.65; font-family: sans-serif;">Powered by <a href="https://www.froala.com/wysiwyg-editor?pb=1" title="Froala Editor">Froala Editor</a></p>

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