Develop Reference

MVC how to change dropdownlist item names

Been googling for a while, but I can't seem to get any closer.
I'm using MVC with an EF Database structure.
I want the dropdownlist items in the View to show up with different names than what they come up with.
Right now, the lambda query returns a list().
I want each item to get a string name depending on their current name. Eventually, the selected field needs to be used in another lambda as the Byte that it was.
Edit
//view
<p>
#using (Html.BeginForm("Index", "Home", FormMethod.Get))
{
<p>
#Html.DropDownList("vbType", (SelectList)ViewBag.Type, "" , new { onchange = "form.submit();" })
....
//controller
var typeLst = new List<byte>();
var typeQry = from t in db.model1
orderby t.TYPE
select t.TYPE;
typeLst.AddRange(typeQry.Distinct());
ViewBag.vbType = new SelectList(typeLst);
....
Thanks in advance.

You can create a SelectListItem to display in your dropdownlist.
Example:
#Html.DropDownListFor(model => model.YearStartedToPay,
Enumerable.Range(DateTime.Today.Year - 60, 61).OrderByDescending(x => int.Parse(x.ToString())).Select(n => new SelectListItem() { Text = n.ToString(), Value = n.ToString(), Selected = false }).ToList<SelectListItem>(),....)
In this case, I'm creating an Enumerable, that will be your list returned from EF, ordering and selecting as a SelectListItem.

You need to make use of dropdownlist's Value property. Make your list a type of SelectListItem.
Assign Text= [Your Required Text] and Value = [Current Name]

DropDownListFor not preselecting value

I'm building an MVC web application and am about to run my head through the wall, there's a dozen topics on this already and all have accepted solutions that do not work for me. There's probably something really stupid and simple I'm forgetting/not seeing, but can't seem to work it out.
Please don't hate me for naming; I'm continuing a project started by someone else.
I have the following line in my ManageDetail.cshtml:
#Html.DropDownListFor(m => m.ChecklistWaarde.SoortID, Model.ChecklistOptionsOptions, "Choose a value", new { #class = "form-control" })
This builds a selectbox based on property Model.ChecklistWaarde.SoortID, which is an integer. The next parameter passed is a SelectList from the model that is generated by the following very simple helper function that does a DB lookup in a 2ndary database (unfortunately), it receives the parameter SoortID as well to set a preselect value:
public SelectList GetChecklistOptions(int selectedId = -1)
{
var soorten = new List<SelectListItem>();
try
{
using (var connection = new SqlConnection(mssqlConnectionString))
{
connection.Open();
SqlCommand command = connection.CreateCommand();
command.CommandText = "Select Naam, ID From ChecklistSoorten";
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
var id = reader["ID"] as int?;
if (id.HasValue)
{
soorten.Add(new SelectListItem { Text = reader["Naam"] as string, Value = id.Value.ToString(), Selected = id.Value.Equals(selectedId) });
}
}
}
}
catch (Exception ex)
{
Globals.Log.Error(ex);
}
return new SelectList(soorten, "Value", "Text");
}
It gets called in the controller like this:
public ActionResult ManageDetail(int? id) {
var model = new MachineDetailsModel(id);
model.ChecklistOptionsOptions = sqlDal.GetChecklistOptions(model.ChecklistWaarde.SoortID);
return View("ManageDetail", model);
}
When I try to debug my code, I can see that the model values are populated correctly:
SoortID has a value of 2 (int)
Model.ChecklistOptionsOptions has a populatedSelectList
Upon inspecting the SelectList I find that only item with value "2" has property Selected = true, this is false for all others.
When the form gets rendered, it will not select the item with value 2, rather it will have the first item selected, "Choose a value"
Inspecting the HTML, I see that the item with value 2 is indeed not selected, contrary to what I was expecting (see HTML below; shorted the list in count and text for readability). I expected to see "selected" on the line for item 2, as it was selected in the SelectList.
<select class="form-control" data-val="true" data-val-number="The field SoortID must be a number." data-val-required="The SoortID field is required." id="ChecklistWaarde_SoortID" name="ChecklistWaarde.SoortID" style="min-width:100%;">
<option value="">Choose a value</option>
<option value="1">Item A</option>
<option value="2">Item B</option>
<option value="3">Item C</option>
<option value="4">Item D</option>
</select>
What am I missing? How can I make item with value "2" select, as it is in the SelectList that I pass to the DropDownListFor() function?

In the controller where you are populating SelectList, set selected value there, your code would look like:
if (id.HasValue)
{
soorten.Add(new SelectListItem
{
Text = reader["Naam"] as string,
Value = id.Value.ToString()
});
}
and then down at the line of instantiating SelectList:
return new SelectList(soorten, "Value", "Text",selectedId);
or you could elminate SelectList and instead in your model change the property ChecklistOptionsOptions type to List<SelectListItem>, in that case the last line of creating SelectList will not be required further, right now you are creating it multiple times.

Ultimately everything in the view that gets rendered comes from ViewData. This takes the model, but also request data and 'ModelState`.
I have had this sort of problem when some of the request parameters have a name conflict with some of the model parameters. This overrides the value in the model and causes the issue.
It is very difficult to debug, as it normally appears that all the correct values have been set. Check all your parameter names if in doubt.

How to display selected value in pre-defined dropdownlist list in asp.net mvc?

I have HTML dropdown list with pre-defined values. I want display one of the specific values from my controller. In a desktop application I would simply write dropdownName.SelectedItem = "";, how can I do this in asp.Net?
If I want to select a specific value (B for example), what will my code be like?
e.g. Request["pName"] = "B";.
Here is my HTML:
<select id="pName" name="pName" class="input-large form-control" style="width:auto">
<option selected disabled>Select Option</option>
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
</select>

Technically you need a select list and a html dropdownlist helper:
public ActionResult SelectCategory() {
var viewModel = new ViewModel();
List<SelectListItem> items = new List<SelectListItem>();
items.Add(new SelectListItem { Text = "A", Value = "A"});
items.Add(new SelectListItem { Text = "B", Value = "B" });
// SelectListItem has a boolean property Selected, which is false by default
items.Add(new SelectListItem { Text = "C", Value = "C", Selected = true });
viewModel.CategoryType = items;
return View();
}
And in your view:
#model ViewModel
#Html.DropDownList("CategoryType")
Please be aware that technically these options for computing the List<SelectListItem> probably are from database and it's better to create a static class for computing this list and other similar lists (which are based on nomenclatures)
Controller code must be clean.

ListItem not highlighted even though selected is true

I am creating a list of months for a list box. The controller captures the selected months and stores them in session for if the user navigates away from the page then returns.
Here is the controller:
public ActionResult Index(int[] Months)
{
if (Session["Months"] == null || Months!= null)
Session["Months"] = Months;
else if (Months== null)
Months= Session["Months"] as int[];
IList<SelectListItem> MonthsList = utility.GetMonths().OrderBy(r => r.Name)
.Select(r => new SelectListItem
{
Text = r.Name,
Value = r.Id.ToString(),
Selected = Months == null ? false : Months.Contains(r.Id)
}).ToList();
var model = new DataModel
{
SelectList = MonthsList,
Data = GetDataByMonths(Months)
};
return (model);
}
Here is the view:
#Html.ListBox("Months", Model.SelectList)
When the user selects items from the ListBox they are highlighted even after the form has been submitted. However when the user navigates away then returns the SelectListItems are correctly labeled as Selected = true but the DOM does not show this.
Any ideas on why this only doesnt work when session is used?
EDIT:
Tried:
#Html.ListBox("Months", new MultiSelectList(Model.Months, "Value", "Text", Model.SelectedMonths), new { size = 8 })
While debugging, the variables show the correct values, they are just not correctly highlighted in the DOM.

Did you try the SelectList type or MultiSelectList rather than an IEnumerable<SelectListItem>? I don't know of any other way to tell the ListBox which property is the value and which is the text.
i.e.
MultiSelectList list = new MultiSelectList(monthsList, "Value", "Text");
and return the list object?

I ended up creating the list box in html rather than using the #html.listbox()
<select name="Months" id="Months" multiple="multiple" size="8">
#foreach (var a in Model.Months)
{
<option value="#a.Value" #(a.Selected.ToString() == "True" ? "selected='selected'" : "")>#a.Text</option>
}
</select>

create a combo box dymically fom list in a viewmodel 9+ mvc

I have in my ViewModel a list that contain 2 ou 3 values:
public class person
{
List<string> civility{get;set;}
string nom {get;set;}
sting prenom {get;set;}
}
how can i create a combobox in the view mapped to civility property. Sometimes we show combobox if the list contain 2 values et sometimes 3 if the list contains 3 and obtain the value in submit

That's technically as easy as:
#Html.DropDownList("FieldName", Model.civility.Select(m => new SelectListItem { Value = m, Text = m }));
You'll end up with something akin to:
<select id="FieldName" name="FieldName">
<option value="CivilityItem1">CivilityItem1</option>
...
</select>
If you want it tied to an actual property on your model (you'll need to add the property to your model first)
#Html.DropDownListFor(m => m.SelectedCivility, Model.civility.Select(m => new SelectListItem { Value = m, Text = m }))