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How to show selected value in a DropDownList Html Helper using ViewBag in C#

So I have the following scenario in which I am using two ViewBag(s):
To get the select list item
To get the particular item in concern
So it looks like this:
var currentType = "2";
List<SelectListItem> contentData = new List<SelectListItem>();
contentData.Add(new SelectListItem
{
Text = "Show 0 only",
Value = "0",
});
contentData.Add(new SelectListItem
{
Text = "Show 2 Only",
Value = "2",
});
ViewBag.currentType = currentType;
ViewBag.contentData = contentData;
Now in my Razor View, I am able to generate the DropDownList like this:
#Html.DropDownList("ContentTypeId", (IEnumerable<SelectListItem>)ViewBag.contentData, null, new { #class = "form-control" , #style = "width: 150px;" })
How can I can bind my ViewBag.currentType on the drop down list so it shows the pre selected value by default when the component is rendered?
Is it even possible to use two ViewBag value in this component ?
I tried like this:
#Html.DropDownList("ContentTypeId", (IEnumerable<SelectListItem>)ViewBag.contentData, null, new { #class = "form-control" , #style = "width: 150px;", #selected= (string)ViewBag.currentType})
But not getting the correct output.
Any tips/suggestions/solutions?

ViewBag is not working in your case, you will have to select an option manually, using Selected=true. HtmlDropDown is an outdated helper too.
Using html5 select with an asp helper is the best way to select item automatically
view
#{
var currentType = "2";
List<SelectListItem> contentData = new List<SelectListItem>();
contentData.Add(new SelectListItem
{
Text = "Show 0 only",
Value = "0",
});
contentData.Add(new SelectListItem
{
Text = "Show 2 Only",
Value = "2",
});
//or I guess you can take the from viewbag
string currentType = ViewBag.currentType;
List<SelectListItem> contentData = ViewBag.currentData
}
.....
<select class="form-control" id="levels" asp-for="#currentType"
asp-items="#contentData">
<option value="0" > Select </option>
</select>
this is working for dropdown list
#{
currentType = ViewBag.currentType;
contentData = ViewBag.contentData;
var dropDownItems = new SelectList(contentData,"Value","Text", currentType);
}
.....
#Html.DropDownList("#currentType",#dropDownItems,"Select",new { #class = "form-control" })

The SelectListItem Class has a Selected property.
You can just do :
List<SelectListItem> contentData = new List<SelectListItem>{
new SelectListItem
{
Text = "Show 0 only",
Value = "0",
},
new SelectListItem
{
Text = "Show 2 Only",
Value = "2",
Selected = true
});

I also wanted to post an answer with the attempt that I had made on this aspect and was able to achieve. I used the standard way of defining the pure HTML element instead of using the Razor helper tags. You can do this if you have dynamic elements which are not a part of your Model:
<select class="form-control" id="ContentDataId" name="ContentDataId">
#foreach (SelectListItem option in ViewBag.contentData as List<SelectListItem>)
{
<option value="#option.Value" #(option.Value == Convert.ToString(ViewBag.currentType) ? "selected='selected'" : "")>#option.Text</option>
}
</select>
The above definition will generate the same HTML if you used the helper tags. For those who have confusion using the helper tags, this is a more conventional way of generating your drop down list with dynamic ViewBag.

ASP.Net Core 5 MVC Populate a drop down list with Database records

Title states what I'm trying to do.
Controller method:
public IActionResult Create()
{
IEnumerable<string> hList = from char s in _context.NR_Users select s.ToString();
List < NR_User > hUsers = new List<NR_User>();
hUsers = (from c in _context.NR_Users select c).ToList();
hUsers.Insert(0, new NR_User { ID = 0, Name = "Select" });
ViewBag.historyUsers = hUsers;
List<SelectListItem> options = new()
{
new SelectListItem { Value = "True", Text = "Yes" },
new SelectListItem { Value = "False", Text = "No" }
};
ViewBag.options = options;
return View();
}
View:
<div class="form-group col-md-4">
<label class="control-label">History PM</label>
<select asp-for="History_PM" name="History_PM" class="form-control" asp-items="#ViewBag.historyUsers"></select>
<span asp-validation-for="History_PM" class="text-danger"></span>
</div>
But when I run the app and navigate to the Create page I get this error:
RuntimeBinderException: Cannot implicitly convert type 'System.Collections.Generic.List<EnvApp.Models.DB.NR_User>' to 'System.Collections.Generic.IEnumerable<Microsoft.AspNetCore.Mvc.Rendering.SelectListItem>'. An explicit conversion exists (are you missing a cast?)
I understand that it can't implicitly convert the list to an IEnumerable, but how exactly do I do that?

You can convert the list using SelectList class.
Try replacing
<select asp-for="History_PM" name="History_PM" class="form-control" asp-items="#ViewBag.historyUsers"></select>
with
<select asp-for="History_PM" name="History_PM" class="form-control" asp-items="#(new SelectList(ViewBag.historyUsers, "ID", "Name"))"></select>

How Can I send selected text to controller from DropdownList

I want to send the selected text field in dropdown to the controller.
When I use the code as follows, I can send the id number to the controllers, but the value I selected in the list pass null.
In addition , if there is a registered value in the model, I want this field to be selected in the dropdownlist when the page is opened.
Controller
public ActionResult Degerlendir(int id ,string CV_STATU)
{
using (MULAKATDBEntities1 ent = new MULAKATDBEntities1())
{
CvViewModel cv = new CvViewModel();
var entData = ent.CV.FirstOrDefault(a => a.ID_CV == id);
entData.CV_STATU = CV_STATU;
ent.SaveChanges();
}
}
In View
#using (Html.BeginForm("Degerlendir", "Home", FormMethod.Post))
{
<input type="hidden" name="id" value="#Model.Cv.ID_CV" />
#Html.DropDownListFor(model => model.Cv.CV_STATU,
new List<SelectListItem> {
new SelectListItem() { Text = "Secilmedi" },
new SelectListItem() { Text = "Kabul edildi" },
new SelectListItem() { Text = "Reddedildi" } },
new {#id="cv_statu", #class = "form-control" })
<input type="submit" id="btnSubmit" value="KAYDET" class="btn btn-add" />
}

Set #name="cv_statu" within the HTML helper htmlAttributes for binding to parameters on POST like this.
Also change the controller method parameter to lowercase cv_statu. Only parameter names passed through URL routes are not case sensitive.

I am assuming that what you shared on your code for your ActionResult is already the HttpPost Action verb. There should be a proper HttpGet as well.
To solve your issue, make sure the first argument that you set on your DropDownListFor should match on the parameter of your Degerlendir
#Html.DropDownListFor(model => model.CV_STATU,
new List<SelectListItem> {
new SelectListItem() { Text = "Secilmedi", Value = "Secilmedi" },
new SelectListItem() { Text = "Kabul edildi", Value = "Secilmedi" },
new SelectListItem() { Text = "Reddedildi", Value = "Reddedildi", Selected = true} }, "Please select an option",
new {#id="cv_statu", #class = "form-control" })
As you notice, I changed your:
#Html.DropDownListFor(model => model.Cv.CV_STATU
To:
#Html.DropDownListFor(model => model.CV_STATU
Because what you set here will set the name attribute on your HTML. This will be binded on your parameter on your ActionResult of Degerlendir particularly your parameter:
string CV_STATU
Lastly, I added Value on your SelectListItem, because that will be passed on your ActionResult whatever you select on your DropDownList. To set the default selected value, just add Selected = true.

Adding SelectListItem manually to SelectList to use in DropDownListFor

When I create a SelecList I wish to be able to add SelecListItem's manually and to do this I use this code:
List<SelectListItem> Provinces = new List<SelectListItem>();
Provinces.Add(new SelectListItem() { Text = "Northern Cape", Value = "NC" });
Provinces.Add(new SelectListItem() { Text = "Free State", Value = "FS" });
Provinces.Add(new SelectListItem() { Text = "Western Cape", Value = "WC" });
SelectList lstProvinces = new SelectList(Provinces);
Instead of this :
var lstProvinces = new SelectList(new[] { "Northern Cape", "Free State", "Western Cape" });
After I created the SelectList, I pass it to the DropDownListFor via the ViewBag :
Html.DropDownListFor(m => m.StartPointProvince, (SelectList)ViewBag.Provinces)
However when I create the SelectList using the first method, it doesn't work - It adds the 3 values to the dropdown list, but all the values display as:
*screenshot of output
However when I use the second method, it works fine.
I wish to use the first method because i want to be able to specify the Text AND value of each item.

The problem is that SelectList(IEnumerable) constructor doesn't accept SelectListItem's (at least not as SelectListItem to add to its Items collection). It simply accepts collection of some arbitrary objects that will be used to generate completely unrelated internal SelectListItems collection.
If you want, you can use SelectList(IEnumerable, string, string) constructor in such way:
List<SelectListItem> Provinces = new List<SelectListItem>();
Provinces.Add(new SelectListItem() { Text = "Northern Cape", Value = "NC" });
Provinces.Add(new SelectListItem() { Text = "Free State", Value = "FS" });
Provinces.Add(new SelectListItem() { Text = "Western Cape", Value = "WC" });
this.ViewBag.Provinces = new SelectList(Provinces, "Value", "Text");
It will work. But it is unnecessary, because you create complex SelectListItem items that won't be used by the SelectList - it will just treat them as any other data object.
In the same way you can just use some other simpler class in place of SelectListItem:
public class SelectListModel
{
public String Text { get; set; }
public String Value { get; set; }
}
...
Provinces.Add(new SelectListModel() { Text = "Northern Cape", Value = "NC" });

Use DropDownList and name it the same as the model's property name. Mine is "ItemType"
#Html.LabelFor(model => model.ItemType, new { #class = "control-label" })
#Html.DropDownList("ItemType", (IEnumerable<SelectListItem>)ViewBag.ItemTypes, new { #class = "form-control" })
#Html.ValidationMessageFor(model => model.ItemType, null, new { #class = "text-danger" })
var types = new List<SelectListItem>();
types.Add(new SelectListItem() { Text = "Select...", Value = string.Empty });
types.Add(new SelectListItem() { Text = "OTC", Value = "0" });
types.Add(new SelectListItem() { Text = "Generic", Value = "1" });
types.Add(new SelectListItem() { Text = "Brand", Value = "2" });
types.Add(new SelectListItem() { Text = "Non-Merchandise", Value = "9" });
ViewBag.ItemTypes = types;
[Required(ErrorMessage = "Item Type is required")]
public Int32 ItemType { get; set; }

you can change your code from
SelectList lstProvinces = new SelectList(Provinces);
to
SelectList lstProvinces = new SelectList(Provinces, "Value", "Text");
and it will display provinces correctly.

You do not need using SelectList.
Instead, put List<SelectListItem> Provinces into ViewBag and return ViewBag.
Then on the View put:
#Html.DropDownList("Dropwonlist", (IEnumerable<SelectListItem>)ViewBag.YourData)

Considering the number of views on this topic, I thought it might help others in giving some further examples of which the option you chose depends on the desired contents of the select list.
I usually prefer to keep the assignment of select dropdown options in a seperate class which is more manageble when creating longer lists, it's also handy to use the same class of optons for more common applications across the app.
C# Class
public class CustomFormsSelectDropdownParams
{
public static IEnumerable<SelectListItem> Example1ItemWidth { get; private set; }
public static IEnumerable<SelectListItem> Example2ItemWidth { get; private set; }
public static List<SelectListItem> Example3ItemWidth { get; private set; }
static CustomFormsSelectDropdownParams()
{
// ---------
// Exmaple 1
// ---------
// This is OK if you only have a
// relatively small amount of options to write.
Example1ItemWidth = new SelectListItem[]
{
// First item different to the remaining range.
new SelectListItem ("100%", "100%"),
new SelectListItem ("5em", "5em"),
new SelectListItem ("6em", "6em"),
new SelectListItem ("7em", "7em"),
new SelectListItem ("8em", "8em"),
new SelectListItem ("9em", "9em"),
new SelectListItem ("10em", "10em")
};
// ---------
// Exmaple 2
// ---------
// This is more practical if you have a large amount of options.
// NOTE: using this example doesnt allow us to insert any options
// that are different from the rest, so limited use cases may apply.
Example2ItemWidth = Enumerable.Range(1, 200).Select(x => new SelectListItem
{
Value = x.ToString() + "em",
Text = x.ToString() + "em",
});
// ---------
// Exmaple 3
// ---------
// This is more practical if you have a large amount of options.
// This example also allows us to add an option that is a different
// to the remaining options in the loop.
// Our first item is bespoke so created seperately.
var firstDefaultItem = new SelectListItem("100%", "100%");
// Provides a range between 10 --> 200em
var remainingItems = Enumerable.Range(10, 191).Select(x => new SelectListItem
{
Value = x.ToString() + "em",
Text = x.ToString() + "em",
});
Example3ItemWidth = new List<SelectListItem>();
// Add out first bespoke item.
Example3ItemWidth!.Add(firstDefaultItem);
// Add the remaining items in a loop.
foreach (var item in remainingItems)
{
Example3ItemWidth.Add(new SelectListItem(item.Text, item.Value));
}
}
}
Sample HTML Code:
<div class="container-fluid">
<div class="row">
<div class="mb-3 col-3" >
<label class="form-label">Example 1</label>
<select class="form-select" asp-items="Classes.CustomForms.CustomFormsSelectDropdownParams.Example1ItemWidth"></select>
</div>
</div>
<div class="row">
<div class="mb-3 col-3" >
<label class="form-label">Example 2</label>
<select class="form-select" asp-items="Classes.CustomForms.CustomFormsSelectDropdownParams.Example2ItemWidth"></select>
</div>
</div>
<div class="row">
<div class="mb-3 col-3" >
<label class="form-label">Example 3</label>
<select class="form-select" asp-items="Classes.CustomForms.CustomFormsSelectDropdownParams.Example3ItemWidth"></select>
</div>
</div>
</div>
All three select dropdowns on the page:
Example 1:
Example 2:
Example 3:
Example 3 was the one that had niggled me for a while, I wasnt sure how to create an select options list as well as adding some other bespoke options at the same time. If i need to to add some more additional besoke options then I would simply add them in what ever order I need, either before the loop, after or in between multiple loops.

How can i create a SelectListItem() with Int Value

I have the folloiwng code inside my asp.net mvc action method:-
var CustomerData = customerlist.Select(m => new SelectListItem()
{
Text = m.SDOrganization.NAME,
Value = m.SDOrganization.ORG_ID.ToString(),
});
currently if i remove the ToString() from the ORG_ID , i will get an error that "can not explicitly convert long to string". so it seems that i have to define both the value and the text for the SelectListItem as strings. but since the SelectListItem should hold long , so is there a way to pass the values of the SelectListItem as long instead of strings?

...so is there a way to pass the values of the SelectListItem as long instead of strings?
No. And it doesn't make any sense to do so as when it is rendered, it's just HTML which has no concept of long.
If we have the action
public ActionResult Test()
{
var dictionary = new Dictionary<int, string>
{
{ 1, "One" },
{ 2, "Two" },
{ 3, "Three" }
};
ViewBag.SelectList = new SelectList(dictionary, "Key", "Value");
return this.View();
}
and the following view "Test.cshtml":
#using (Html.BeginForm())
{
#Html.DropDownList("id", ((SelectList)ViewBag.SelectList), "All")
<input type="submit" value="Go" />
}
The generated HTML is
<form action="/home/test" method="post">
<select id="id" name="id">
<option value="">All</option>
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
</select>
<input type="submit" value="Go">
</form>
and when we post to this action, text of your number is effectively parsed back into your desired type by the Model Binder
[HttpPost]
public ActionResult Test(int? id)
{
var selectedValue = id.HasValue ? id.ToString() : "All";
return Content(String.Format("You selected '{0}'", selectedValue));
}
And the above works as you might expect.