DropDownList不能在ASP.Net中工作100％MVC

Question

我很困惑如何有效地使用ASP.NET MVC的Html.DropDownList助手。

背景：我有一個5頁的表單，每次單擊「下一步」時將數據保存到表單中。用戶可以在部分之間來回導航，因此以前的部分將已經預填充了先前輸入的數據。

這適用於TextBoxes。但不是DropDownLists。我曾嘗試不同的方法的負載，包括：

• How to add static list of items in MVC Html.DropDownList()
• Setting selected item to DropdownList in MVC Application?

我有一個視圖模型等taht我有我的名單，我的模型（生成的LINQ到SQL類）作爲屬性。例如：

public class ConsultantRegistrationFormViewModel 
{ 
    public IConsultantRegistration ConsultantRegistration { get; private set; } 

    public SelectList Titles { get; private set; } 
    public SelectList Countries { get; private set; } 
    public SelectList Currencies { get; private set; } 
    public int CurrentSection { get; private set; } 

    private ConsultantRegistrationFormViewModel(IConsultantRegistration consultantRegistration) 
    { 
     ConsultantRegistration = consultantRegistration; 


     CurrentSection = 1; 

     Titles = new SelectList(new string[] { "Mr", "Mrs", "Miss", "Ms", "Dr", "Sir" }); 
     Countries = new SelectList(countries.Select(q => q.Name)); 
     Currencies = new SelectList(currencies,"CurrencyCode","FriendlyForm"); 
    } 
} 

上得到我的控制器的編輯操作是這樣的：

public class ConsultantRegistrationController : Controller 
{ 
     public IConsultantRegistrationRepository ConsultantRegistrationRepository { get; private set; } 
     public ICountryRepository CountryRepository { get; private set; } 
    public IEnumerable<ICountry> Countries { get; private set; } 

    public ConsultantRegistrationController() 
    { 
     ConsultantRegistrationRepository = RepositoryFactory.CreateConsultantRegistrationRepository(); 
     CountryRepository = RepositoryFactory.CreateCountryRepository(); 

     Countries = CountryRepository.GetCountries().ToArray(); 
    } 


    public ActionResult Edit(Guid id, int sectionIndex) 
    { 
     IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id); 

     SelectList bankBranchCountriesSelectList = new SelectList(Countries, "BankBranchCountry", "CountryName", consultantRegistration.BankBranchCountry); 
     ViewData["bankBranchCountrySelectList"] = bankBranchCountriesSelectList; 

     return View(new ConsultantRegistrationFormViewModel(consultantRegistration,sectionIndex, Countries,Currencies)); 
    } 
} 

我的觀點做：

 <%: Html.DropDownList("ConsultantRegistration.BankBranchCountry",ViewData["bankBranchCountrySelectList"] as SelectList) %> 

這給我的錯誤：

DataBinding: 'IWW.ArrowPay.ConsultantRegistration.Data.Country' does not contain a property with the name 'BankBranchCountry'.

它所做的，看看架構此屬性的：

public interface IConsultantRegistration 
{ 
    Guid ID { get; set; } 


    [DisplayName("Branch Country")] 
    string BankBranchCountry { get; set; } 

} 

（我的LINQ到SQL類型ConsultantRegistration實現IConsultantRegistration）

看來，它正試圖綁定到錯誤類型有關係嗎？

如果我用這個在我看來（和使用我的控制器的國家屬性）：

 <%: Html.DropDownList("ConsultantRegistration.BankBranchCountry ",Model.Countries,"(select a Country)") %> 

我得到保存的值很好，但我的模型不會在之後的更新。

如果我用這個在我看來：在我的視圖模型

 <%: Html.DropDownListFor(model=>model.ConsultantRegistration.BankBranchCountry ",Model.Countries,"(select a Country)") %> 

我得到的名單，並將其職位所選擇的值改回，但不預先選擇當前選定的項目。

所以我有一個解決方案遍佈各地，但不是全部在一個地方。

希望你能幫助填補我的無知。

Answer 1

好吧，我解決了這個問題。適當的哈克，但它完成了工作。

我使用的ViewData在我看來：

   <%: Html.DropDownList("bankBranchCountrySelectList", ViewData["bankBranchCountrySelectList"] as SelectList)%> 

在我的控制下：

 public ActionResult Edit(Guid id, int sectionIndex) 
     { 
      IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id); 

      ViewData["bankBranchCountrySelectList"] = Countries.Select(q => new SelectListItem() { Text = q.Name, Value = q.Name, Selected = (q.Name.Trim().Equals(consultantRegistration.BankBranchCountry, StringComparison.InvariantCultureIgnoreCase)) }); // bankBranchCountriesSelectList; 

      return View(new ConsultantRegistrationFormViewModel(consultantRegistration,sectionIndex, Countries,Currencies)); 
     } 



     [AcceptVerbs(HttpVerbs.Post)] 
     public ActionResult Edit(Guid id, int sectionIndex, FormCollection formValues) 
     { 
      IConsultantRegistration consultantRegistration = ConsultantRegistrationRepository.GetConsultantRegistration(id); 

      UpdateModel(consultantRegistration); 
        ViewData["bankBranchCountrySelectList"] = Countries.Select(q => new SelectListItem() { Text = q.Name, Value = q.Name, Selected = (q.Name.Trim().Equals(consultantRegistration.BankBranchCountry, StringComparison.InvariantCultureIgnoreCase)) }); 

      IEnumerable<RuleViolation> ruleViolations = consultantRegistration.GetRuleViolations(sectionIndex); 
      if (ruleViolations.Count() == 0) 
      { 

// ... 
      } 
      else 
      { 
       ModelState.AddRuleViolations(ruleViolations); 
       return View(new ConsultantRegistrationFormViewModel(consultantRegistration, sectionIndex, Countries, Currencies)); 
      } 


    } 

不理想中斷清潔編碼。不知道它爲什麼起作用，但這似乎是MVC關於「約定優於配置」的全部內容。

Answer 2

文章在考慮多選擇列表寫的，但其原理同樣適用於單一選擇下拉列表：

http://www.stevefenton.co.uk/Content/Blog/Date/201002/Blog/How-To-Handle-Multiple-Select-Lists-In-ASP-NET-MVC/