MVC下拉列表设置所选值

Question

Hey I have tried following to set the selected value for dropdownlist. In My controller:

u.Roles = new List<AspNetRole>();
foreach (var role in db.AspNetRoles)
{
    u.Roles.Add(role);
}

And in my View:

 @Html.DropDownList(Model.role.Id, new SelectList(Model.Roles, "Id", "Name"), htmlAttributes: new { @class = "form-control"})

But still not working, I did not got the selected value. When debugging I can see that Model.role.Id contains the selected value.

Note also that the Id is of type string, because it is hashed. What I am doing wrong?

Answer 1

There are few ways of display DropDownList in MVC. I like the following approach.

Note: You need a collection of SelectListItem in model.

Model

public class MyModel
{
    public int SelectedId { get; set; }
    public IList<SelectListItem> AllItems { get; set; }

    public MyModel()
    {
        AllItems = new List<SelectListItem>();
    }
}

Controller

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new MyModel();
        model.AllItems = new List<SelectListItem>
        {
            new SelectListItem { Text = "One",  Value = "1"},
            // *** Option two is selected by default ***
            new SelectListItem { Text = "Two",  Value = "2", Selected = true},
            new SelectListItem { Text = "Three",  Value = "3"}
        };
        return View(model);
    }

    [HttpPost]
    public ActionResult Index(MyModel model)
    {
        // Get the selected value
        int id = model.SelectedId;
        return View();
    }
}

View

@model DemoMvc.Controllers.MyModel
@using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
    @Html.DropDownListFor(x => x.SelectedId, Model.AllItems)
    <input type="submit" value="Submit" />
}