c# - MVC 4 编辑控制器/查看多对多关系和复选框

Question

我正在使用 ASP.NET MVC 4 和实体框架，我正在寻找某种方法来从我的数据库中为创建/编辑控制器和视图创建多对多关系和复选框，我找到了@Slauma 的答案在MVC 4 中创建 - 多对多关系和复选框 ，但是，我真的很想看看它如何扩展到编辑和删除功能以及此解决方案中的其他合作伙伴。有人可以展示我将如何在 Edit 控制器方法中填充 ClassificationSelectViewModel 以获得“选中”和“未选中”值吗？这是一个 Matt Flowers 的问题，也可以解决我的问题。

Answer 1

以下是此答案的延续，描述Create了实体之间具有多对多关系的模型的 GET 和 POST 操作，Subscription这Company.是Edit我将如何执行操作的过程（除了我可能不会把所有EF 代码到控制器操作中，但将其提取到扩展和服务方法中）：

CompanySelectViewModel保持不变：

public class CompanySelectViewModel
{
    public int CompanyId { get; set; }
    public string Name { get; set; }
    public bool IsSelected { get; set; }
}

SubscriptionEditViewModel是SubscriptionCreateViewModel加号的Subscription关键属性：

public class SubscriptionEditViewModel
{
    public int Id { get; set; }
    public int Amount { get; set; }
    public IEnumerable<CompanySelectViewModel> Companies { get; set; }
}

GET动作可能如下所示：

public ActionResult Edit(int id)
{
    // Load the subscription with the requested id from the DB
    // together with its current related companies (only their Ids)
    var data = _context.Subscriptions
        .Where(s => s.SubscriptionId == id)
        .Select(s => new
        {
            ViewModel = new SubscriptionEditViewModel
            {
                Id = s.SubscriptionId
                Amount = s.Amount
            },
            CompanyIds = s.Companies.Select(c => c.CompanyId)
        })
        .SingleOrDefault();

    if (data == null)
        return HttpNotFound();

    // Load all companies from the DB
    data.ViewModel.Companies = _context.Companies
        .Select(c => new CompanySelectViewModel
        {
            CompanyId = c.CompanyId,
            Name = c.Name
        })
        .ToList();

    // Set IsSelected flag: true (= checkbox checked) if the company
    // is already related with the subscription; false, if not
    foreach (var c in data.ViewModel.Companies)
        c.IsSelected = data.CompanyIds.Contains(c.CompanyId);

    return View(data.ViewModel);
}

Edit视图是Create视图加上 的 key 属性的隐藏Subscription字段Id：

@model SubscriptionEditViewModel

@using (Html.BeginForm()) {

    @Html.HiddenFor(model => model.Id)
    @Html.EditorFor(model => model.Amount)

    @Html.EditorFor(model => model.Companies)

    <input type="submit" value="Save changes" />
    @Html.ActionLink("Cancel", "Index")
}

选择公司的编辑器模板保持不变：

@model CompanySelectViewModel

@Html.HiddenFor(model => model.CompanyId)
@Html.HiddenFor(model => model.Name)

@Html.LabelFor(model => model.IsSelected, Model.Name)
@Html.EditorFor(model => model.IsSelected)

POST 动作可能是这样的：

[HttpPost]
public ActionResult Edit(SubscriptionEditViewModel viewModel)
{
    if (ModelState.IsValid)
    {
        var subscription = _context.Subscriptions.Include(s => s.Companies)
            .SingleOrDefault(s => s.SubscriptionId == viewModel.Id);

        if (subscription != null)
        {
            // Update scalar properties like "Amount"
            subscription.Amount = viewModel.Amount;
            // or more generic for multiple scalar properties
            // _context.Entry(subscription).CurrentValues.SetValues(viewModel);
            // But this will work only if you use the same key property name
            // in ViewModel and entity

            foreach (var company in viewModel.Companies)
            {
                if (company.IsSelected)
                {
                    if (!subscription.Companies.Any(
                        c => c.CompanyId == company.CompanyId))
                    {
                        // if company is selected but not yet
                        // related in DB, add relationship
                        var addedCompany = new Company
                            { CompanyId = company.CompanyId };
                        _context.Companies.Attach(addedCompany);
                        subscription.Companies.Add(addedCompany);
                    }
                }
                else
                {
                    var removedCompany = subscription.Companies
                       .SingleOrDefault(c => c.CompanyId == company.CompanyId);
                    if (removedCompany != null)
                        // if company is not selected but currently
                        // related in DB, remove relationship
                        subscription.Companies.Remove(removedCompany);
                }
            }

            _context.SaveChanges();
        }

        return RedirectToAction("Index");
    }

    return View(viewModel);
}

Delete动作难度较小。在该GET操作中，您可以加载一些订阅属性以显示在删除确认视图上：

public ActionResult Delete(int id)
{
    // Load subscription with given id from DB
    // and populate a `SubscriptionDeleteViewModel`.
    // It does not need to contain the related companies

    return View(viewModel);
}

然后在POST操作中加载实体并删除它。不需要包括公司，因为在多对多关系（通常）中，链接表上的级联删除已启用，以便数据库将负责删除链接条目以及父项Subscription：

[HttpPost, ActionName("Delete")]
public ActionResult DeleteConfirm(int id)
{
    var subscription = _context.Subscriptions.Find(id);
    if (subscription != null)
        _context.Subscriptions.Remove(subscription);

    return RedirectToAction("Index");
}