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Can I specify the default for a SelectListItem in the .cshtml?

I have a set of dropdown values defined in a global .cs file:
mydropdowns.cs
public class Foo_DropdownValues
{
public static List<SelectListItem> NoYes { get; } = new List<SelectListItem>
{
new SelectListItem { Value = "false", Text = "No"},
new SelectListItem { Value = "true", Text = "Yes" }
};
...
I'm using these SelectLists in different places in my .cshtml web form:
mypage.cshtml
<div class="form-group" id="PC_QU10_div">
<label>#Foo_Questions.QU10</label>
<select asp-for="Foo_Answers.QU10" asp-items="Foo_DropdownValues.NoYes"></select>
</div>
<div class="form-group" id="PC_QU20_div">
<label>#Foo_Questions.QU20</label>
<select asp-for="Foo_Answers.QU20" asp-items="Foo_DropdownValues.NoYes"></select>
...
I'd like to specify a default of "Yes" for the first item, and a default of "No" for the second?
Q: Is there any way for my to specify an explicit default in the .cshtml markup? On a per-item basis?
My app is written in C# in .Net Core 3.1, if it matters.

When a view has a model type specified, input controls for each of the properties of model object can be created using either the HTML Helper methods (#Html.TextBoxFor, #Html.CheckBoxFor, #Html.RadioButtonFor, #Html.DropdownListFor) etc. or using asp-for attributes in the input controls.
Both of these above mentioned ways, makes sure that the value entered/selected in the input control will be assigned to the model object properties when form is submitted and also the input controls are populated with the respective property values from the model object if the model object is being passed to the view from the server.
That's why, in this particular case, if the dropdown needs to have a specific value pre-selected (or by default selected), a value needs to be assigned to the dropdownlist. And it can be easily done by populating value in the property of the model object.
Consider example below:
Model class:
public class PersonData
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string Gender { get; set; }
public bool IsMarried { get; set; }
public bool IsLeftHanded { get; set; }
}
Static list of items for dropdownlist.
public static class StaticValues
{
public static SelectListItem[] Genders
{
get
{
return new SelectListItem[]
{
new SelectListItem("Male", "Male"),
new SelectListItem("Female", "Female")
};
}
}
public static SelectListItem[] YesNoItems
{
get
{
return new SelectListItem[]
{
new SelectListItem("Yes", "True"),
new SelectListItem("No", "False")
};
}
}
}
View Code:
#model PersonData;
#{
ViewData["Title"] = "Person data";
}
<div>
<label asp-for="FirstName">Firstname:</label>
<input asp-for="FirstName"/>
</div>
<div>
<label asp-for="LastName">Lastname:</label>
<input asp-for="LastName" />
</div>
<div>
<label asp-for="Gender">Firstname:</label>
<select asp-for="Gender" asp-items="#StaticValues.Genders"></select>
</div>
<div>
<label asp-for="IsMarried">Married:</label>
<select asp-for="IsMarried" asp-items="#StaticValues.YesNoItems"></select>
</div>
<div>
<label asp-for="IsLeftHanded">Left handed:</label>
<select asp-for="IsLeftHanded" asp-items="#StaticValues.YesNoItems"></select>
</div>
In the following code from Controller Action method, model object is populated with a few properties with values assigned to them. And the model object is passed to the View.
public async Task<IActionResult> Index()
{
var personData = new PersonData();
// This assignment should populate the text box with John value
personData.FirstName = "John";
// Gender dropdown should have Male pre-selected
personData.Gender = "Male";
// IsMarried dropwodn should have "Yes" pre-selected.
personData.IsMarried = true;
return View(personData);
}
Following is the view rendered when application is run.
In a different use case, there can be a requirement where a specific value needs to be pre-selected by default when model property does not have value assigned to the property.
In such situations, specific SelectListItem should have Selected property set to true.
For example, in below list of SelectListItem New York has true passed as third argument in constructor. That will mark that item as selected be-default in the dropdownlist.
public static SelectListItem[] OfficeLocations
{
get
{
return new SelectListItem[]
{
new SelectListItem("London", "LON"),
new SelectListItem("New York", "NY", true),
new SelectListItem("Singapore", "SG")
};
}
}
Now I will add new property OfficeLocation to PersonData class as following.
public string OfficeLocation { get; set; }
And add following code to view.
<div>
<label asp-for="OfficeLocation">Office location:</label>
<select asp-for="OfficeLocation" asp-items="#StaticValues.OfficeLocations"></select>
</div>
Now if the model object does not have any value assigned to OfficeLocation property, the OfficeLocation dropdown will have New York selected by default.
The view will look as following.
I hope this will help you resolve your issue.

There are 2 options that I know of that can work depending on requirements:
1.) Add a disabled default option directly in the mark-up
<select ...>
<option disabled value="">Choose an option</option>
</select>
2.) Set the default selected value in your PageModel / Code behind before returning the view. If you want to continue to use a static reference for the common list, you can create a static method that takes a bool selected parameter instead of a readonly property:
var items = new List<SelectListItem>();
...
items.Insert(0, new SelectListItem("No", "No", selected: true));
//..insert other items

Using DropdownListFor - Value is being set using Jquery, Displayed in Console too, but Null at Controller

Here is the Syntax of My Dropdown.
#Html.DropDownListFor(model => model.DealerIdRef, Model.Ddllist, " Select Dealer ", new { #class = "form-control"})
i want its default selected value and make it read-only so that user can not update selection. For this i'm using Jquery.
$('#DealerIdRef').val('#Session["MyID"]').trigger('change');
$("#DealerIdRef").attr('disabled', 'true');
this is setting the value and also exists in Console
At Controller it is still null
Edit
if i'm making some mistake then please help.
thanks in advance

Your javascript is setting the disabled attribute of the dropdownlist. Disabled form controls do not submit a value so the value of DealerIdRef in your model is its default (i.e. null because its int?).
If you want the value of the dropdownlist to be submitted, do not disabled it.
But based on i want its default selected value and make it read-only so that user can not update selection, then there is no point generating a dropdownlist, and in anycase, you set selected option by setting the value of the property your binding to. That is you set the value of DealerIdRef in the GET method before you pass the model to the view.
Since all you want is to display a value and have it posted back, then include a hidden input for the value and display the text
#Html.HiddenFor(m => m.DealerIdRef)
<div>...the txt you want to display...</div>
There is no point degrading performance by generating a SelectList and extra html when its not needed.
As a side note, your POST method would have throw this exception because you have not repopulated the SelectList in the POST method before you return the view.

I wrote a simple mock your question.
It can work. The simple code is on DropDownController
Here is the Source Code,I Upload to github.
ViewModel
public class DropDownViewModel
{
[Display(Name = "Dealer")]
public int? DealerIdRef { get; set; }
public IEnumerable<SelectListItem> Ddllist { get; set; }
}
Index View
Mock Your Submit action
#model Sample.Models.DropDownViewModel
#using (Html.BeginForm("ShowDDL", "DropDown", FormMethod.Post))
{
#Html.DropDownListFor(model => model.DealerIdRef, Model.Ddllist, " Select Dealer ", new { #class = "form-control" })
<button>Submit</button>
}
ShowDDL View
Show your select data.
#model Sample.Models.DropDownViewModel
<b>Your Select Value: </b> #Model.DealerIdRef
DropDownController
public ActionResult Index()
{
DropDownViewModel model = new DropDownViewModel()
{
Ddllist = GetDDL(),
DealerIdRef = 1
};
return View(model);
}
[HttpPost]
public ActionResult ShowDDL(DropDownViewModel viewModel)
{
return View(viewModel);
}
private IEnumerable<SelectListItem> GetDDL()
{
return new List<SelectListItem>()
{
new SelectListItem()
{
Text = "One",
Value = "1"
},
new SelectListItem()
{
Text = "Two",
Value = "2"
}
};
}

Show list after select DropDownList value Razor

I've been working for a while on this, I know how to resolve it using JQuery, but I need to solve this just using server side code, I'm in a Razor View
The thing is:
I have an #Html.DropDownlist that is showing some States from USA, and once clicked one of the States from the DropDownList then I want to show some cities that belong to the State selected using other DropDownList, I'm not sure how to get the value from the selected field just using Razor syntax and then show the cities that belong to the State in other DropDownList when one State is selected, I'm using a SelectList and I have an StateID to bind the cities... I'm showing all the States inside a DropDownList that is working.
Here is my code:
These are just two classes that I'm using to fill the SelectList with some properties:
public States(int id, string name, List<string> list)
{
StateID = id;
Name = name;
Cities = list;
}
public int StateID { get; set; }
public string Name { get; set; }
public List<string> Cities { get; set; }
}
public static class Fill
{
public static List<States> GiveMeStates()
{
List<States> li = new List<States>() {
new States(1, "Alabama",new List<string> {"Adamsville", "Addison", "Anderson","Anniston", "Arab" }),
new States(2,"Alaska", new List<string> {"Anchorage","Juneau","Fairbanks","Sitka"}),
new States(3,"Arizona", new List<string> { "Avondale", "Benson", "Besbee"})
};
return li;
}
}
And now this is my Razor View:
#using RazorMVC.Models;
#{
List<States> aux = Fill.GiveMeStates();
SelectList states = new SelectList(aux, "StateID", "Name");
}
<form>
#Html.DropDownList("ddlStates", states);
</form>

If you absolutely do not want to use javascript/jQuery, you may submit the form (with the selected state id) and get the states based on the posted state id and show that.
Assuming you want to show the cities for the selected state in the same view.
#{
var stateId = Request.QueryString["ddlStates"] as string;
List<States> aux = Fill.GiveMeStates();
SelectList states = new SelectList(aux, "StateID", "Name");
List<SelectListItem> cities = new List<SelectListItem>();
if (!String.IsNullOrEmpty(stateId))
{
var state = aux.FirstOrDefault(f => f.StateID == Convert.ToInt32(stateId));
if (state != null)
{
cities = state.Cities
.Select(x => new SelectListItem {Value = x, Text = x}).ToList();
}
}
}
<label>Select a state and hit submit </label>
#using (Html.BeginForm("Index", "Home", FormMethod.Get))
{
#Html.DropDownList("ddlStates", states)
<label>Cities < /label>
#Html.DropDownList("City", cities)
<input type="submit" />
}
I personally prefer to not put a lot of C# code in the razor views. I usually create a view model and use that to pass the values needed in the view. So most of the above code you see in the view goes in my action method.
If you prefer to use jQuery/javascript (Why not ?), You may listen to the change event of the the first dropdown ,get the selected option value and send that to server via an ajax call. Let your server action method returns the states in json format and your ajax metod's call back can parse the json data and update the cities dropdown. Here is a sample to start with

How to display dynamic dropdownlists in Edit view with selected values in .NET MVC?

I have a form, which includes three dynamic dropdownlists. They are all one-to-many relationships. The first dropdownlist has loaded values and the other two are empty at the start. When user selects one value from the 1st dropdownlist, the 2nd dropdownlist will load corresponding items; when user selects a value from the 2nd dropdownlist, the 3rd dropdownlist will load relating items.
User can create the form and submit. My CreateController GET and POST methods works well.
Now I need EditController to allow user to edit his form. The problem is how to display the 2nd and the 3rd dynamic dropdownlist with selected values?
In my viewModel:
public Nullable<int> Tech_ID { get; set; }
public string TechniqueName { get; set; }
public SelectList Techniques { get; set; }
public Nullable<int> BU_ID { get; set; }
public string BuName { get; set; }
public SelectList BusinessUnits { get; set; }
In my Edit Controller:
ViewBag.Bulist = new SelectList(AllBus, "BU_ID", "BU_Title", form.BU_ID);
var butechList = GetTechList(Convert.ToInt32(form.BU_ID));
IEnumerable<SelectListItem> butechs = butechList.Select(m => new SelectListItem()
{
Value = m.Tech_ID.ToString(),
Text = m.Technique.Tech_Title
});
ViewBag.Techlist = new SelectList(butechs, "Tech_ID", "Tech_Title", form.Tech_ID);
in View page:
#Html.DropDownListFor(model => model.BU_ID,
new SelectList((IEnumerable<SelectListItem>)#ViewBag.Bulist, "Value", "Text", Model.BU_ID),
new { id = "ddlBU" })
#Html.DropDownListFor(model => model.Tech_ID,
new SelectList((IEnumerable<SelectListItem>)#ViewBag.Techlist, "Value", "Text", Model.Tech_ID),
new { id = "ddlTechs" })
The first dropdownlist is working correctly, but the second is not.

Firstly, you have a view model containing SelectList properties, so make use of it rather than using ViewBag properties.
Next, delete the unnecessary last parameter (object selectedValue) in you SelectList constructors - your binding to a property in your model so it is ignored (internally the DropDwonListFor() method generated a new IEnumerable<SelectListItem> and sets the selectedValue based on the value of the property your binding to)
But the main issue is that your unnecessarily generating 3 IEnumerable<SelectListItem>. The first using
IEnumerable<SelectListItem> butechs = butechList.Select(...
which is correct. Then you try and create another one form it using
ViewBag.Techlist = new SelectList(butechs, "Tech_ID", "Tech_Title", form.Tech_ID);
but this time it will throw an exception because butechs is IEnumerable<SelectListItem> and SelectListItem does not contain properties Tech_ID and Tech_Title (it would need to be new SelectList(butechs, "Value", "Text") to prevent the error, but its pointless so just delete it). And then you try to create a 3rd IEnumerable<SelectListItem> inside the DropDownListFor() method (again its pointless extra ovehead).
Your code in the controller simply needs to be
var butechList = GetTechList(form.BU_ID.Value); // its already an int!
model.Techniques = new SelectList(butechList, "Tech_ID", "Tech_Title");
return View(model);
and in the view
#Html.DropDownListFor(m => m.Tech_ID, Model.Techniques) // not sure why you would need to change the id from the default id="Tech_ID" to id="ddlBU"?
I also suggest you study the code in this DotNetFiddle which shows an example of generating cascading dropdownlists. In particular the code in the private void ConfigureViewModel(ViewModel model) method, which will generate the correct SelectList's based on selected values, and can be called from both the Create() and Edit() methods (both the GET and the POST if you need to return the view)

How to add values to dropdown in MVC3?

I want to add a dropdownlist in my form, with 2 values userid and username in my dropdownlist, and also I want to get the value selected by the user when I click the button. I'm new to MVC and so far, I have not worked on dropdownlist, tried few samples but nothing seems to be working the way I want.

I'll jump lots of MVC3 concepts. If you're really new to ASP.NET MVC, you should take a look at some tutorials.
This code should help you:
VIEW
#using (Html.BeginForm("ACTION NAME", "CONTROLLER NAME"))
{
<select name="select">
<option value="username" selected>User name</option>
<option value="userid">User id</option>
</select>
<input type="submit" />
}
ACTION
[HttpPost]
public ActionResult ACTIONNAME(string select)
{
//...
}
Please, note:
ACTION NAME and CONTROLLER NAME at the BeginForm helper. You will have to modify this at your code
The select name ("select") and the name of the argument at the action ("select"). This is not a coincidence, it's a convention. MVC uses the name attr to bind data
The selected attribute at the option will make it the default option
Regards

See one of the ways you can do it is send the list in a model property as the binding and for the value you can bind it to another property like :
public class YourModel
{
public List<UserList> OptionList { get; set; }
public String YourValue{get;set;}
}
public class UserList
{
public String UserName{get;set;}
public String UserId{get;set;}
}
#Html.DropDownListFor(model => model.YourValue, Model.OptionList, "")
In the helper there are overided options which are used to specify the value and text.
And Remember :
This is StackOverflow.
Even the Not working example which you have tried are important for the ones who try to help you since they are spending their precious bandwidths for u.

You don't need create a new model class for each view, just put this on controller:
ViewBag.FieldName = new SelectList(new List<SelectListItem>() {
new SelectListItem { Value = "userid", Text = "User ID" },
new SelectListItem { Value = "username", Text = "User name" }
});
And this on view:
#Html.DropDownList("FieldName")

You need to create a collection of SelectListItem like:
IEnumerable<SelectListItem> selectList =
from c in areaListResponse.Item
select new SelectListItem
{
Text = c.AreaName,
Value = c.Id.ToString()
};
Pass this selectList to your view:
return View(selectList);
In your cshtml:
#model IEnumerable<SelectListItem>
#Html.DropDownListFor(m => m.RequestAreaName, Model)
If you need complecated object, you may need a wrapper class like:
public class RaiseRequestModelWrapper
{
public IEnumerable<SelectListItem> GetModel { get; set; }
public RaiseRequestModel PostModel { get; set; }
}