how to get selected drow down list value in Action

问题:

In MVC web app it is a view with strongly typed model where a drop down is being generated / bind by model.

Below is view code:

@model LoanViewModel    
<form class="wrapper minheight homeloan-form border-top" id="homeloan-form" method="post" action="LeadContact" novalidate="novalidate">

<p>@Html.ValidationSummary()</p>
<p>Select an Item : @Html.DropDownListFor(x => x.HomeLoanLead.Items, new SelectList(Model.HomeLoanLead.Items), "--Choose any Item--")</p>

<div class="formnav row">
            <button class="">Show Top Home Loans <i class="fa fa-chevron-right"></i></button>    
        </div>
</form>

In model I m hardcoding options for drop down list:

 public List<string> Items 
    { 
        get { _items = new List<string>(); 
            _items.Add("One"); 
            _items.Add("Two"); 
            _items.Add("Three"); 
            return _items; 
        } 
    }

On post back I cant get what was selected value in drop down. Please guide me how to get in post action which drop down value was selected.

回答1:

A simple example of using Html.DropDownFor() to display a list of options and bind to a property:

Model

public class LoanViewModel
{
  [Required]
  [Display(Name="Select Item")]
  public string Item { get; set; }

  public SelectList ItemList { get; set; }
}

Controller

public ActionResult Edit()
{
  LoanViewModel model = new LoanViewModel();
  model.Item = "Two"; // this will now pre-select the second option in the view
  ConfigureEditModel(model);
  return View(model);
}

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(LoanViewModel model)
{
  if (!ModelState.IsValid)
  {
    ConfigureEditModel(model); // repopulate select list
    return View(model); // return the view to correct errors
  }
  // If you want to validate the the value is indeed one of the items
  ConfigureEditModel(model);
  if (!model.ItemList.Contains(model.Item))
  {
    ModelState.AddModelError(string.Empty, "I'm secure!");
    return View(model);
  }

  string selectedItem = model.Item;
  ....
  // save and redirect
}

private void ConfigureEditModel(LoanViewModel model)
{
  List<string> items = new List<string>() { "One", "Two", "Three" };
  model.ItemList = new SelectList(items); // create the options
  // any other common stuff
}

View

@model LoanViewModel
@using (Html.BeginForm())
{
  @Html.AntiForgeryToken()
  @Html.ValidationSummary(true)

  @Html.DisplayFor(m => m.Item)
  @Html.DropDownListFor(m => m.Item, Model.ItemList), "--Choose any Item--")
  @Html.ValidationMessageFor(m => m.Item)

  <input type="submit" value="Submit" />
}