Asp.Net MVC：如何在提交时从 DropDownListFor 中获取选定的选项

Question

I have dropdownlist in Asp.net form and after selected option on submit doesn't getting value in Action.

Not getting what im missing and selected options not retrieving in Action .Here is the code

ViewPage

<div class="inner-box">

        @using ICommonInterfaces.Model
        @model LoginModel
        @using (Html.BeginForm("ApplicationSwitcher", "Home", FormMethod.Get))
        {
          @Html.DropDownListFor(m => m.ApplicationNames, new SelectList(Model.ApplicationNames, "TenantId", "ApplicationId"), "Select Application",
       new { @class = "textboxStyle", placeholder = "Select your application...", autofocus = "autofocus",
         autocomplete = "on", onkeypress = "btnFocusActivate(this, event)", id = "un" })
          <input type="submit" value="NEXT" class="rectangle" id="submitNext" disabled="disabled" />
        }       
</div>

Model

namespace ICommonInterfaces.Model
{
    public class LoginModel
    {
        public List<TenantApplicationNames> ApplicationNames { get; set; }
    }

    public class TenantApplicationNames
    {
        public string TenantId { get; set; }
        public string ApplicationId { get; set; }
    }
}

On Submit HomeController Action

    [HttpGet]
    public async Task<IActionResult> ApplicationSwitcher(LoginModel loginModel)
    {
      var applicationNames = loginModel.ApplicationNames; // Count zero
      Console.WriteLine(applicationNames.Count)//0
    }

what is the reason not getting selected options?How to get it?

Thanks.

Answer 1

I'd change the method to POST and get the value of selected item using Request.Form["nameOfYourDDL"]

Like:

<div class="inner-box">

    @using ICommonInterfaces.Model
    @model LoginModel
    @using (Html.BeginForm("ApplicationSwitcher", "Home", FormMethod.Post))
    {
      @Html.DropDownListFor("ddlTest", m => m.ApplicationNames, new SelectList("ddlTeste", Model.ApplicationNames, "TenantId", "ApplicationId"), "Select Application",
   new { @class = "textboxStyle", placeholder = "Select your application...", autofocus = "autofocus",
     autocomplete = "on", onkeypress = "btnFocusActivate(this, event)", id = "un" })
      <input type="submit" value="NEXT" class="rectangle" id="submitNext" disabled="disabled" />
    }   

And in the controller:

    [HttpPost]
public async Task<IActionResult> ApplicationSwitcher(LoginModel loginModel)
{
     var selectedValue = Request.Form["ddlTest"].ToString
}

Answer 2

I test the form that is generated by @using (Html.BeginForm() . In controller, loginModel receives data with the type of array. In order to get the drop-down list's value in the controller, this code need to be modified.

In ViewPage, m.ApplicationNames need to be changed to array. m.ApplicationNames[0].TenantId

<div class="inner-box">

    @using ICommonInterfaces.Model
    @model LoginModel
    @using (Html.BeginForm("ApplicationSwitcher", "Home", FormMethod.Get))
    {
        @Html.DropDownListFor(m => m.ApplicationNames[0].TenantId, new SelectList(Model.ApplicationNames, "TenantId", "ApplicationId"), "Select Application",
     new
     {
         @class = "textboxStyle",
         placeholder = "Select your application...",
         autofocus = "autofocus",
         autocomplete = "on",
         onkeypress = "btnFocusActivate(this, event)",
         id = "un",
     })
        <input type="submit" value="NEXT" class="rectangle" 
         id="submitNext" @*disabled="disabled"*@ />
    }
</div>

Result.