C# 在那里有导航属性。如果启用了延迟加载（默认情况下是这样），则导航属性将最终为null。我建议OP研究“急切加载”，以便使用您的解决方案。 public ActionResult Edit(int id) { Users result = null;

在那里有导航属性。如果启用了延迟加载（默认情况下是这样），则导航属性将最终为

null

。我建议OP研究“急切加载”，以便使用您的解决方案。

public ActionResult Edit(int id)
{
    Users result = null;
    using (MyApplicationContext context = new MyApplicationContext())
    {
        ViewBag.Conditions = context.Conditions.Where(x => x.IsActive).OrderBy(x => x.Name).ToList();
        result = context.Users.FirstOrDefault(x => x.Id == id);
    }
        return View("Manage", result);
}

@using MyApplicationContext.Models
@model MyApplication.Models.Users

@{
    ViewBag.Title = "Manage";
    List<MyApplication.Models.Condition> conditionList = ViewBag.Conditions;

    foreach (var condition in conditions)
    {
        bool isChecked = Model.Conditions.Any(x => x.Id == condition.Id) ? true : false;
    }

// Include this namespace:
using System.Data.Entity;

result = context.Users
    .Include(u => u.Conditions) // <-- Instruct the query to also load Conditions.
    .FirstOrDefault(x => x.Id == id);