Question

I am using asp.net mvc 4
Is there a way to update the form based on selection made by the user?

(in this case I want to fill in address fields if something is picked from the dropdown list, otherwise a new address would need to be typed in)

My model:
public class NewCompanyModel
{

    [Required]
    public string CompanyName { get; set; }
    public bool IsSameDayRequired { get; set; }

    public int AddressID { get; set; }
    public Address RegisterOfficeAddress { get; set; }
}

View:

@model ViewModels.NewCompanyModel


@using (Html.BeginForm(null, null, FormMethod.Post, new { name = "frm", id = "frm" }))
{
@Html.ValidationSummary(true)

<fieldset id="test">
    <legend>Company</legend>


        <h2>Register office address</h2>

        <div class="editor-label">
            @Html.LabelFor(model => model.AddressID)
        </div>
        <div class="editor-field">
            @Html.DropDownListFor(model => model.AddressID, (IList<SelectListItem>)ViewBag.Addresses, new {id = "address", onchange = "window.location.href='/wizard/Address?value=' + this.value;" })
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.RegisterOfficeAddress.BuildingNameOrNumber)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.RegisterOfficeAddress.BuildingNameOrNumber)
            @Html.ValidationMessageFor(model => model.RegisterOfficeAddress.BuildingNameOrNumber)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.RegisterOfficeAddress.StreetName)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.RegisterOfficeAddress.StreetName)
            @Html.ValidationMessageFor(model => model.RegisterOfficeAddress.StreetName)
        </div>

and controller:

 public ActionResult Address(string value)
    {
      //get the address from db and somehow update the view
    }

The question is how do you update the ‘model.RegisterOfficeAddress.StreetName’ etc
Just to make clear this is just part of the form so I cannot submit it just yet.

Many thanks

Answer 1

Thanks for your help; I have decided to take a different approach:
On dropdown change I submit the form:

<div class="editor-label">
        @Html.LabelFor(model => model.ServiceAddress.AddressID)
    </div>
    <div class="editor-field">
        @Html.DropDownListFor(model => model.ServiceAddress.AddressID, (IEnumerable<SelectListItem>)ViewBag.Addresses, new { onchange = "this.form.submit();" })
        @Html.ValidationMessageFor(model => model.ServiceAddress.AddressID)
    </div>

and then in controller:

  [HttpPost]
        public ActionResult NewDirector(NewDirectorVM vm, string value)
        {
            ModelState.Clear();
            if (vm.ServiceAddress.AddressID > 0)
            {
               //Updates the properties of the viewModel
               vm.ServiceAddress = _Repository.GetAddress(vm.ServiceAddress.AddressID);
            }
   return View("NewDirector", vm);
}

Please notice ModelState.Clear(); which actually allows the view to be updated from the controller (otherwise all the changes made the the viewModel by the controller would have been overwritten by the values in the view).