How to get DropDownList SelectedValue in Controlle

问题:

I have dropdownlist, which I have filled from database. Now I need to get the selected value in Controller do some manipulation. But not getting the idea. Code which I have tried.

Model

public class MobileViewModel 
{          
    public List<tbInsertMobile> MobileList;
    public SelectList Vendor { get; set; }
}

Controller

 public ActionResult ShowAllMobileDetails()
    {
        MobileViewModel MV = new MobileViewModel();
        MV.MobileList = db.Usp_InsertUpdateDelete(null, \"\", \"\", null, \"\", 4, MergeOption.AppendOnly).ToList();
        MV.Vendor = new SelectList(db.Usp_VendorList(), \"VendorId\", \"VendorName\");
        return View(MV);
    }

    [HttpPost]
    public ActionResult ShowAllMobileDetails(MobileViewModel MV)
    {           
        string strDDLValue = \"\"; // Here i need the dropdownlist value

        return View(MV);
    }

View

   <table>           
        <tr>
            <td>Mobile Manufacured</td>
            <td>@Html.DropDownList(\"ddlVendor\", Model.Vendor, \"Select Manufacurer\") </td>
        </tr>         
        <tr>
            <td>

            </td>
            <td>
                <input id=\"Submit1\" type=\"submit\" value=\"search\" />
            </td>
        </tr>
    </table>

回答1:

1st Approach (via Request or FormCollection):

You can read it from Request using Request.Form , your dropdown name is ddlVendor so pass ddlVendor key in the formCollection to get its value that is posted by form:

string strDDLValue = Request.Form[\"ddlVendor\"].ToString();

or Use FormCollection:

[HttpPost]
public ActionResult ShowAllMobileDetails(MobileViewModel MV,FormCollection form)
{           
  string strDDLValue = form[\"ddlVendor\"].ToString();

  return View(MV);
}

2nd Approach (Via Model):

If you want with Model binding then add a property in Model:

public class MobileViewModel 
{          
    public List<tbInsertMobile> MobileList;
    public SelectList Vendor { get; set; }
    public string SelectedVendor {get;set;}
}

and in View:

@Html.DropDownListFor(m=>m.SelectedVendor , Model.Vendor, \"Select Manufacurer\")

and in Action:

[HttpPost]
public ActionResult ShowAllMobileDetails(MobileViewModel MV)
{           
   string SelectedValue = MV.SelectedVendor;
   return View(MV);
}

UPDATE:

If you want to post the text of selected item as well, you have to add a hidden field and on drop down selection change set selected item text in the hidden field:

public class MobileViewModel 
{          
    public List<tbInsertMobile> MobileList;
    public SelectList Vendor { get; set; }
    public string SelectVendor {get;set;}
    public string SelectedvendorText { get; set; }
}

use jquery to set hidden field:

<script type=\"text/javascript\">
$(function(){
$(\"#SelectedVendor\").on(\"change\", function {
   $(\"#SelectedvendorText\").val($(this).text());
 });
});
</script>

@Html.DropDownListFor(m=>m.SelectedVendor , Model.Vendor, \"Select Manufacurer\")
@Html.HiddenFor(m=>m.SelectedvendorText)

回答2:

Model

Very basic model with Gender field. GetGenderSelectItems() returns select items needed to populate DropDownList.

public enum Gender 
{
    Male, Female
}

public class MyModel
{
    public Gender Gender { get; set; }

    public static IEnumerable<SelectListItem> GetGenderSelectItems()
    {
        yield return new SelectListItem { Text = \"Male\", Value = \"Male\" };
        yield return new SelectListItem { Text = \"Female\", Value = \"Female\" };
    }
}

View

Please make sure you wrapped your @Html.DropDownListFor in a form tag.

@model MyModel

@using (Html.BeginForm(\"MyController\", \"MyAction\", FormMethod.Post)
{
   @Html.DropDownListFor(m => m.Gender, MyModel.GetGenderSelectItems())
   <input type=\"submit\" value=\"Send\" />
}

Controller

Your .cshtml Razor view name should be the same as controller action name and folder name should match controller name e.g Views\\MyController\\MyAction.cshtml.

public class MyController : Controller 
{
    public ActionResult MyAction()
    {
        // shows your form when you load the page
        return View();
    }

    [HttpPost]
    public ActionResult MyAction(MyModel model)
    {
        // the value is received in the controller.
        var selectedGender = model.Gender;
        return View(model);
    }
}

---

Going further

Now let\'s make it strongly-typed and enum independent:

var genderSelectItems = Enum.GetValues(typeof(Gender))
    .Cast<string>()
    .Select(genderString => new SelectListItem 
    {
        Text = genderString,
        Value = genderString,
    }).AsEnumerable();

回答3:

If you\'re looking for something lightweight, I\'d append a parameter to your action.

[HttpPost]
public ActionResult ShowAllMobileDetails(MobileViewModel MV, string ddlVendor)
{           
    string strDDLValue = ddlVendor; // Of course, this becomes silly.

    return View(MV);
}

What\'s happening in your code now, is you\'re passing the first string argument of \"ddlVendor\" to Html.DropDownList, and that\'s telling the MVC framework to create a <select> element with a name of \"ddlVendor.\" When the user submits the form client-side, then, it will contain a value to that key.

When MVC tries to parse that request into MV, it\'s going to look for MobileList and Vendor and not find either, so it\'s not going to be populated. By adding this parameter, or using FormCollection as another answer has suggested, you\'re asking MVC to specifically look for a form element with that name, so it should then populate the parameter value with the posted value.

回答4:

Use SelectList to bind @HtmlDropdownListFor and specify selectedValue parameter in it.

http://msdn.microsoft.com/en-us/library/dd492553(v=vs.108).aspx

Example : you can do like this for getting venderid

@Html.DropDownListFor(m => m.VendorId,Model.Vendor)


   public class MobileViewModel 
   {          
    public List<tbInsertMobile> MobileList;
    public SelectList Vendor { get; set; }
    public int VenderID{get;set;}
   }
   [HttpPost]
   public ActionResult Action(MobileViewModel model)
   {
            var Id = model.VenderID;

回答5:

I was having the same issue in asp.NET razor C#

I had a ComboBox filled with titles from an EventMessage, and I wanted to show the Content of this message with its selected value to show it in a label or TextField or any other Control...

My ComboBox was filled like this:

 @Html.DropDownList(\"EventBerichten\", new SelectList(ViewBag.EventBerichten, \"EventBerichtenID\", \"Titel\"), new { @class = \"form-control\", onchange = \"$(this.form).submit();\" })

In my EventController I had a function to go to the page, in which I wanted to show my ComboBox (which is of a different model type, so I had to use a partial view)?

The function to get from index to page in which to load the partial view:

  public ActionResult EventDetail(int id)
        {

            Event eventOrg = db.Event.Include(s => s.Files).SingleOrDefault(s => s.EventID == id);
            //  EventOrg eventOrg = db.EventOrgs.Find(id);
            if (eventOrg == null)
            {

                return HttpNotFound();
            }
            ViewBag.EventBerichten = GetEventBerichtenLijst(id);
            ViewBag.eventOrg = eventOrg;
            return View(eventOrg);
        }

The function for the partial view is here:

 public PartialViewResult InhoudByIdPartial(int id)
        {
            return PartialView(
                db.EventBericht.Where(r => r.EventID == id).ToList());

        }

The function to fill EventBerichten:

        public List<EventBerichten> GetEventBerichtenLijst(int id)
        {
            var eventLijst = db.EventBericht.ToList();
            var berLijst = new List<EventBerichten>();
            foreach (var ber in eventLijst)
            {
                if (ber.EventID == id )
                {
                    berLijst.Add(ber);
                }
            }
            return berLijst;
        }

The partialView Model looks like this:

@model  IEnumerable<STUVF_back_end.Models.EventBerichten>

<table>
    <tr>
        <th>
            EventID
        </th>
        <th>
            Titel
        </th>
        <th>
            Inhoud
        </th>
        <th>
            BerichtDatum
        </th>
        <th>
            BerichtTijd
        </th>

    </tr>

    @foreach (var item in Model)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.EventID)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Titel)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Inhoud)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.BerichtDatum)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.BerichtTijd)
            </td>

        </tr>
    }
</table>

VIEUW: This is the script used to get my output in the view

<script type=\"text/javascript\">
    $(document).ready(function () {
        $(\"#EventBerichten\").change(function () {
            $(\"#log\").ajaxError(function (event, jqxhr, settings, exception) {
                alert(exception);
            });

            var BerichtSelected = $(\"select option:selected\").first().text();
            $.get(\'@Url.Action(\"InhoudByIdPartial\")\',
                { EventBerichtID: BerichtSelected }, function (data) {
                    $(\"#target\").html(data);
                });
        });
    });
            </script>
@{
                    Html.RenderAction(\"InhoudByIdPartial\", Model.EventID);
                } 

<fieldset>
                <legend>Berichten over dit Evenement</legend>
                <div>
                    @Html.DropDownList(\"EventBerichten\", new SelectList(ViewBag.EventBerichten, \"EventBerichtenID\", \"Titel\"), new { @class = \"form-control\", onchange = \"$(this.form).submit();\" })
                </div>

                <br />
                <div id=\"target\">

                </div>
                <div id=\"log\">

                </div>
            </fieldset>

回答6:

Thanks - this helped me to understand better ansd solve a problem I had. The JQuery provided to get the text of selectedItem did NOT wwork for me I changed it to

$(function () {
  $(\"#SelectedVender\").on(\"change\", function () {
   $(\"#SelectedvendorText\").val($(**\"#SelectedVender option:selected\"**).text());
  });
});

回答7:

If you want to use @Html.DropDownList , follow.

Controller:

var categoryList = context.Categories.Select(c => c.CategoryName).ToList();

ViewBag.CategoryList = categoryList;

View:

@Html.DropDownList(\"Category\", new SelectList(ViewBag.CategoryList), \"Choose Category\", new { @class = \"form-control\" })

$(\"#Category\").on(\"change\", function () {
 var q = $(\"#Category\").val();

console.log(\"val = \" + q);
});

回答8:

MVC 5/6/Razor Pages

I think the best way is with strongly typed model, because Viewbags are being aboused too much already :)

MVC 5 example

Your Get Action

public async Task<ActionResult> Register()
    {
        var model = new RegistrationViewModel
        {
            Roles = GetRoles()
        };

        return View(model);
    }

Your View Model

    public class RegistrationViewModel
    {
        public string Name { get; set; }

        public int? RoleId { get; set; }

        public List<SelectListItem> Roles { get; set; }
    }    

Your View

    <div class=\"form-group\">
        @Html.LabelFor(model => model.RoleId, htmlAttributes: new { @class = \"col-form-label\" })
        <div class=\"col-form-txt\">
            @Html.DropDownListFor(model => model.RoleId, Model.Roles, \"--Select Role--\", new { @class = \"form-control\" })
            @Html.ValidationMessageFor(model => model.RoleId, \"\", new { @class = \"text-danger\" })
        </div>
    </div>                                   

Your Post Action

    [HttpPost, ValidateAntiForgeryToken]
    public async Task<ActionResult> Register(RegistrationViewModel model)
    {
        if (ModelState.IsValid)
        {
            var _roleId = model.RoleId, 

MVC 6 It\'ll be a little different

Get Action

public async Task<ActionResult> Register()
    {
        var _roles = new List<SelectListItem>();
        _roles.Add(new SelectListItem
        {
           Text = \"Select\",
           Value = \"\"
        });
        foreach (var role in GetRoles())
        {
          _roles.Add(new SelectListItem
          {
            Text = z.Name,
            Value = z.Id
          });
        }

        var model = new RegistrationViewModel
        {
            Roles = _roles
        };

        return View(model);
    }

Your View Model will be same as MVC 5

Your View will be like

<select asp-for=\"RoleId\" asp-items=\"Model.Roles\"></select>

Post will also be same

Razor Pages

Your Page Model

[BindProperty]
public int User User { get; set; } = 1;

public List<SelectListItem> Roles { get; set; }

public void OnGet()
{
    Roles = new List<SelectListItem> {
        new SelectListItem { Value = \"1\", Text = \"X\" },
        new SelectListItem { Value = \"2\", Text = \"Y\" },
        new SelectListItem { Value = \"3\", Text = \"Z\" },
   };
}

<select asp-for=\"User\" asp-items=\"Model.Roles\">
    <option value=\"\">Select Role</option>
</select>

I hope it may help someone :)