Develop Reference

Get selected item of DropDownListFor and using it to create new list

Have some problems trying to solve this. Have two DropDownListFor where the first is populated with data and the second should be populated using the selected value from the first.
Lets say the first DropDownlist contains these data:
RoutesList;
Value = "CoOs", Text = "Copenhagen - Oslo",
Value = "StOs", Text = "Stockholm - Oslo",
Value = "OsCo", Text = "Oslo - Copenhagen"
In my razor view I'm trying to create a new list based on the selected value.
How do I get the selected value, lets say "StOs" and format it so it only contains the first two letters "St"? Trying to do this with C# and not Jquery.
My code
// Loads RoutesList to departureRouteSelectList
var departureRouteSelectList = Model.RoutesList;
// Finds selected value
var selectedItem = departureRouteSelectList.Select(x => x.Value);
// Create new selectList for returnRoute
List<SelectListItem> returnRouteSelectList = null;
I'm not sure if the "Select" command does what I want and getting the "StOs"?

Understanding what you want make me think this post will resolve your problem:
Can't get my DropDownListFor to select a selected SelectListItem item in a Dropdown menu

Multiple default selected items in Listbox

I'm looking into creating an Edit page for a Company object that has multiple categories (that are predefined in a list). I have the list being sent through the ViewBag, and have the categories that the user selected in the Create page in an Array thanks to a ViewModel.
I can't figure out a way to have the ListBox prepopulate with the multiple values in my array. I was playing around with jQuery and was able to get one of the values to be selected, but when I try more than one nothing shows up. Any ideas?
#Html.ListBox("Category", new SelectList(ViewBag.Category, "Text", "Value"))

The SelectListItem object has a Selected property to indicate this. So I guess it would come down to how you build the SelectList. Currently you do this:
new SelectList(ViewBag.Category, "Text", "Value")
Which works, but gives you no control over the individual SelectListItems. Instead of building a SelectList, you can build an IEnumerable<SelectListItem> using the same method overload. Initially that might look like this:
ViewBag.Category.Select(c => new SelectListItem
{
Text = c.Text,
Value = c.Value
});
At this point you have more control over the individual items. Now it's just a matter of determining which ones should be selected. How do you determine that? Is it a property on the Category object? Something like this?:
ViewBag.Category.Select(c => new SelectListItem
{
Text = c.Text,
Value = c.Value,
Selected = c.Selected
});
Or perhaps some other condition?:
ViewBag.Category.Select(c => new SelectListItem
{
Text = c.Text,
Value = c.Value,
Selected = c.SomeValue == SomeCondition
});
How you determine that is up to you, and ideally something you can logically add to the backing model being used here.

SelectList selected item not staying set

I have a drop down on my site that has a number of languages in it. When a user selects a different language, the page text reloads to that language. I would like the language drop down to change to reflect that by specifying the selected index of the selected language. However when ever I do this, the drop down in HTML does not change and always displays the first item in the list.
I have the following ViewModel :
public class BaseViewModel
{
public BaseViewModel()
{
}
public IEnumerable<SelectListItem> LanguageSelectListItems { get; set; }
}
The LanguageSelectListItems property is populated successfully when I construct a list of SelectListItems. When this is passed into the view, the selected language SelectListItem is set to true - in this case Swedish. All good so far.
But when the view calls Html.DropDownList() the selected languages' selected property changes to false. A couple of pictures might explain this better.
Before calling #Html.DropDownList("language", Model.LanguageSelectListItems)
Immediately after #Html.DropDownList("language", Model.LanguageSelectListItems)
You can see that the Selected property for the Swedish language has changed to false on the SelectListItem, and this is the resultant HTML :
<select name="language" id="language">
<option value="2">English</option>
<option value="3">Finnish</option>
<option value="4">Swedish</option>
</select>
Any ideas why this might be happening ?
Edit: LanguageSelectListItems is being populated and the selected language being set using this function (where languages is an enumerable of language) :
public static IEnumerable<SelectListItem> GetLanguageList(int selectedIndex)
{
var selectListItems = new List<SelectListItem>();
foreach (var language in languages)
{
selectListItems.Add(new SelectListItem() { Text = language.Name, Value = language.Id });
}
if (selectedIndex >= 0)
{
selectListItems[selectedIndex].Selected = true;
}
return selectedListItems;
}

Well if anyone else finds themselves in this strange situation, the solution to my problem was this.
In the controller action method before returning the view with the SelectList drop down, there was this line of code :
ViewBag.language = Model.Language;
This seemed to be interfering with the way the SelectList was being constructed in the view :
#Html.DropDownList("language", Model.LanguageSelectListItems)
After removing this line from the controller the SelectList started defaulting to the correct value. This fixed both Html.DropDownList and Html.DropDownListFor. I also discovered this in another area of the site where the behaviour was the same, but this time a ViewData[""] was being used.
So if you do run into this problem, check your local areas for any uses of ViewBag and ViewData that use the same name as the property you are trying to construct the drop down for.

How to detect if a check box is selected using MVC3 Razor

As I am new to MVC framework, I have been spending a couple of hours to generate a check box list in a View file. Finally, I could figure it out well. Here is my code:
#foreach (var item in Model.GetRoleNames)
{
#Html.CheckBox("chk_" + item.Value, new { value = item.Value })#item.Text<br />
}
But, I need to detect which of them is selected and if all the ckeckboxes are left unchecked, then preventing some operations.
Question: How can I get the checked items when I am within a controller action?

As the others said, you should use a Boolean value as the second parameter to CheckBox to indicate the checked status. A bit of string manipulation should help you get the ids of the selected check boxes..
First lets change the way the checkbox helper is used
<div id='myCheckboxDiv'>
#foreach (var item in Model.GetRoleNames)
{
#Html.CheckBox("chk_" + item.Value, false)#item.Text<br />
}
</div>
As you can see, I have set the second parameter to false and wrapped the mix in a div
And, when you want to get the ‘values’ associated with the selected checkboxes
var values = $(‘# myCheckboxDiv’).find('input:checkbox:checked').map(function () {
// get the name ..
var nameOfSelectedItem = this.attr('name');
// skip the ‘chk_’ part and give me the rest
return nameOfSelectedItem.substr(4);
}).get();
I am assuming item.Value to be a number. If its is not, please remove the white spaces using C#

Getting an ID of a value from dropdown list

Hey,
I Have three IQueryable lists which i concat together into one list to be displayed in the dropdown box. But now I want to get the id of what the user selected since there are 3 lists to choose from. Thanks
Example:
IQueryable<Store> stores= _storeRepository.FindAll().OrderBy(c => c.Description);
var storeList = stores.ToSelectList("StoreId", "Description", viewModel.StoreId.ToString());
IQueryable<Product> products = _productRepository.FindAll().OrderBy(j => j.Name);
var productList = products.ToSelectList("ProductId", "Name", viewModel.ProductId.ToString());
var viewList = storeList.Concat(productList).ToList();
viewModel.Lookups = viewList; //display in dropdown

if you question was i have 3 lists and the user choose one how can i know which one he chosen
Answer :
you give all three the same name and the value will change depend on which one the user have chosen
if your question was i want to send the id value with the selected list
Answer :
the server doesn't have any info about your html attributes
just the name attribute which maps to the action method parameter name and the value which maps to the parameter value , you can't know the id value and other attributes in the server
Example :
<input type="text" name="Title" id="SomeValue"/>
Will Map To :
public ActionResult Index(string Title)
the server will not recive id="SomeValue"
Solution :
What you can do is place a hidden field under every item with the value you want

instead of this way, after concatenating do this
viewdata["viewList"] = storeList.Concat(productList).ToList();
and view display items in dropdown like this
<%= Html.DropDownList("viewlist_id", (List<SelectListItem>)ViewData["viewlist"])%>
now use a submit button (if want to post the data to same action else use actionlink with routvalues if redirecting to different action,I am using here submit button)
<input type="submit" name="submit" value="submit" />
and in your action you can retrieve the posted data
var dropdown_id = Request.Form["viewlist_id"];
this way you will get the id of selected drop down. thanks

So i figured out how to have the values of different lists combined into one dropdown list will still being able to access its actual value or ID without concat or union- the code is a lot if anyone is interested i will go ahead and take the time to properly post it. Other than that, thank you everyone for offer your advise and help. Thanks

So this is how i went about my problem. In my Controller File - in my Get method after the button click this is what i did:
resultSummaryViewModel.Value = value;
resultSummaryViewModel.ReportFrame = new FramedViewModel();
if(value !="")
{
string viewValue = value.Substring(0, value.IndexOf("|"));
string viewType = value.Substring(value.IndexOf("|") + 1);
resultSummaryViewModel.ReportFrame.SourceURL =
WebPathHelper.MapUrlFromRoot(
string.Format(
"Reporting/ResultSummary.aspx?beginDate={0}&endDate={1}&Id={2}&viewType={3}",
resultSummaryViewModel.BeginDate, resultSummaryViewModel.EndDate, viewValue,
viewType));
}
var viewData = new Dictionary<string, string>();
viewData.Add("Schools", "|allschools");
viewData.Add("Classes", "|allclasses");
This is also connected to my display page aspx.cs which contains the actual lists i use to populate.