How to fetch selected value from a dropdownlist in

问题:

This may sound simple but i am stuck up at a very strange problem.

I have created dropdown's in my application and i am not able to fetch the selected value On Edit.

Here is my View:

<div class="editor-field">
      @Html.DropDownListFor(model => model.Hobbyhome.HobbyHomeAddressList.First().ProvincialState.ProvincialStateID, new SelectList(ViewBag.State, "ProvincialStateID", "ProvincialStateName"), "-----Select State-----", new { @id = "State" })<font color="red">*</font> 
      </div>

i have written a function in controller to fetch the value and i am also able to fetch the value but when it goes in View it doesnot show me the value
i have created another dropdown like this:

  @Html.DropDownListFor(model => model.Hobbydetail.Hobbymaster.HobbyId, new SelectList(ViewBag.Hobby, "HobbyId", "HobbyName"), "----Select Hobby----", new { @id = "Hobby" })<font color="red">*</font> 

And the strange thing is i can see the value of the second dropdown but not for first One
What i think is maybe because i am using an list.First() in the first dropdown and so it isgiving this problem bcoz On edit view page it only shows me "-----Select State--" as value for first dropdown.
Please Help me

回答1:

To get the "selected value object" in you edit view :

@Html.DropDownListFor(model => model.Hobbydetail.Hobbymaster.HobbyId, 
    new SelectList(ViewBag.Hobby, "HobbyId", "HobbyName", Model.Hobbydetail.Hobbymaster.HobbyId),
    "----Select Hobby----", new { @id = "Hobby" })

To have all elements in your DropDown, be sure that your ViewBag.Hobby is initialized and filled in your controller before showing Edit view!

回答2:

First() method returns the first element of a sequence. It will throw you an exception if the source sequence is empty.

Why you need to use First() there ? I think you are doing it in the wrong way. your first paramenter of DropDownListFor should be a variable which holds the selected value, in this purticular overload you are using.

public static MvcHtmlString DropDownList(
    this HtmlHelper htmlHelper,
    string name,
    IEnumerable<SelectListItem> selectList,
    IDictionary<string, Object> htmlAttributes
)

name : The name of the form field to return.

You should be using the second approach

I would make a clean ViewModel to handle this. This makes my Views Clean.

public class AddHobbyViewModel
{
  public int SelectedHobbyId { set;get;}
  public IEnumerable<Hobby> Hobbys { set;get;}
  //other relevant properties for the View.  
}

In the GET action method, Instead of returning the data in ViewBag, I would return it in the ViewModel.

public ActionResult Add()
{
  AddHobbyViewModel model=new AddHobbyViewModel ();
  model.Hobbys=db.Hobbies();  // get all available hobbies.

  return View(model);
}

And in the View,

 @Html.DropDownListFor(model => SelectedHobbyId , new SelectList(Hobbys , "HobbyId", "HobbyName"), "----Select Hobby----", new { @id = "Hobby" })

Now you will have the selected value available in your httppost mehod in the SelectedHobbyId property

[HttpPost]
public ActionResult Add(AddHobbyViewModel model)
{
  // check model.SelectedHobbyId here
}