无法更新Question实体中的枚举属性问题排查

错误提示：

标记助手‘option’不得在元素的属性声明区域包含C#代码。

相关代码 #

Question.cs #

using quiz.Entities;
using System.ComponentModel;

public class Question
{
    public Guid Id { get; set; }

    [DisplayName("Question's Text")]
    public string QuestionText { get; set; }

    public enum DifficultyLevel
    {
        Easy,
        Medium,
        Hard
    }

    [DisplayName("Zorluk Derecesi")]
    public DifficultyLevel Difficulty { get; set; }

    [DisplayName("Şık A")]
    public string AnswerA { get; set; }

    [DisplayName("Şık B")]
    public string AnswerB { get; set; }

    [DisplayName("Şık C")]
    public string AnswerC { get; set; }

    [DisplayName("Şık D")]
    public string AnswerD { get; set; }

    [DisplayName("Doğru Şık")]
    public char CorrectAnswer { get; set; }

    [DisplayName("Movie Name (MovieId)")]
    public Guid MovieId { get; set; }

    public virtual Movie? Movie { get; set; }
}

Edit.cshtml #

<div class="form-group mb-4">
 <label asp-for="Difficulty" class="form-label font-weight-bold">Zorluk Derecesi</label>
 <select asp-for="Difficulty" class="form-control bg-secondary text-light border-0 shadow-sm">
     <option value="">Seçiniz</option>
     @foreach (var level in Enum.GetValues(typeof(Question.DifficultyLevel)))
     {
         <option value="@level.ToString()" @(Model.Difficulty == level ? "selected" : "")>@level</option>
     }
 </select>
 <span asp-validation-for="Difficulty" class="text-danger"></span>

错误根源是ASP.NET Core的option标记助手不允许在属性声明区域直接嵌入C#代码（此处的三元表达式属于属性内的C#逻辑），提供两种解决办法：

方法一：使用枚举绑定标记助手（推荐） #

ASP.NET Core内置了枚举下拉框的快捷绑定方式，无需手动循环，自动处理选中状态：

<div class="form-group mb-4">
 <label asp-for="Difficulty" class="form-label font-weight-bold">Zorluk Derecesi</label>
 <select asp-for="Difficulty" asp-items="Html.GetEnumSelectList<Question.DifficultyLevel>()" class="form-control bg-secondary text-light border-0 shadow-sm">
     <option value="">Seçiniz</option>
 </select>
 <span asp-validation-for="Difficulty" class="text-danger"></span>
</div>

Html.GetEnumSelectList会自动生成枚举所有选项，并匹配当前Model.Difficulty的值设置selected属性。

方法二：手动循环时拆分逻辑 #

如果坚持手动构建选项，可将选中状态提前赋值给变量，避免在属性内直接写C#代码：

<div class="form-group mb-4">
 <label asp-for="Difficulty" class="form-label font-weight-bold">Zorluk Derecesi</label>
 <select asp-for="Difficulty" class="form-control bg-secondary text-light border-0 shadow-sm">
     <option value="">Seçiniz</option>
     @foreach (var level in Enum.GetValues(typeof(Question.DifficultyLevel)))
     {
         string selected = Model.Difficulty == level ? "selected" : "";
         <option value="@level.ToString()" @selected>@level</option>
     }
 </select>
 <span asp-validation-for="Difficulty" class="text-danger"></span>
</div>

内容的提问来源于stack exchange，提问作者onurkaygn