I'm stucked at creating dropdownlist in ASP.NET MVC.
ViewModel:
public MultiSelectList users { get; set; }
I set the values in controller:
var allUsers = db.Users.Select(u => new {
id = u.UserId,
name = u.Name
}).ToList();
model.users = new MultiSelectList(allUsers, "id", "name");
so selectbox values are set.
In view:
#Html.DropDownListFor(m => m.users, Model.users, new { #class = "form-control" })
The problem is that if I select the value and click submit i get this error:
No parameterless constructor defined for this object.
I think the problem is in the way how I create the dropdownlist in view, I'm not sure how to set it, thanks.
EDIT: If I dont choose any user from dropdown all goes well, but if I choose then the error appears.
You're trying to post to the MultiSelectList property. That's not going to work regardless, but the specific error is related to the fact that MultiSelectList has no parameterless constructor, and there's no way for the modelbinder to new up a class with parameters. Anything involved in the modelbinding process must have a parameterless constructor.
What you should be doing is have an additional property like:
public List<int> SelectedUserIds { get; set; }
And, then bind to that in your view:
#Html.ListBoxFor(m => m.SelectedUserIds, Model.Users)
Also, as you'll notice, I changed DropDownListFor to ListBoxFor. If you're wanting to have a select multiple, you need ListBoxFor.
Looks like it is failing when trying to bind, so to prevent it from binding:
[HttpPost]
public ActionResult YourMethod([Binding(Exclude = "users")] SomeViewModel model)
The post back should go to an IEnumerable to capture the selected items.
Add to view model
public IEnumerable UserList { get; set; }
Change view to
#Html.DropDownListFor(m => m.UserList, Model.users, new { #class = "form-control" })
If you want get selected user id from a dropdownlist you must add a property to your model
public MultiSelectList users { get; set; }
public int SelectedUser { get;set;}
And in view
#Html.DropDownListFor(m => m.SelectedUser, Model.users, new { #class = "form-control" })
Related
Hi I am trying to Bind my dropdown list in MVC from a model.
Here is my model
[Table("FileConfig")]
public class FileConfigModel
{
[Key]
[Display(Name = "File Congif ID")]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int FileConfigId { get; set; }
....
[Display(Name = "Description")]
public string Description { get; set; }
}
Here is my getall method in the controller:
public List<FileConfigModel> GetAll()
{
return db.FileConfigModels.ToList();
}
Then I am calling it from my another controller
public ActionResult Create()
{
var fileConfigListEntries = new FileConfigController().GetAll()
.Select(fc => new SelectListItem
{
Value = fc.FileConfigId.ToString(),
Text = fc.Description,
Selected = false
});
ViewBag.FileConfigEntires = fileConfigListEntries;
return View();
}
And here is my view:
#Html.LabelFor(model => model.FileConfigId, new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.DropDownListFor(model => model.FileConfigId, ViewBag.FileConfigEntires as SelectList, "-Select File Config")
#Html.ValidationMessageFor(model => model.FileConfigId)
</div>
However, I've been keep getting error saying
"There is no ViewData item of type 'IEnumerable' that has the key 'FileConfigId'.."
Could someone please help me and tell me what I've missed.
Your query for fileConfigListEntries (i.e. ..Select(fc => new SelectListItem{ .. }) returns IEnumerable<SelectListItem>
In the view, you then try and convert that to typeof SelectList using ViewBag.FileConfigEntires as SelectList
SelectList is IEnumerable<SelectListItem>, but IEnumerable<SelectListItem> is not SelectList, therefore the conversion fails, and the 2nd parameter of DropDownListFor() is null. When the 2nd parameter is null, the method expects the 1st parameter to be IEnumerable<SelectListItem> which it is not, hence the exception.
Change your code to
#Html.DropDownListFor(m => m.FileConfigId, ViewBag.FileConfigEntires as IEnumerable<SelectListItem>, ... )
or
#Html.DropDownListFor(model => model.FileConfigId, (IEnumerable<SelectListItem>)ViewBag.FileConfigEntires, ... )
Side note There is no point setting Selected = false in the .Select clause - its false by default, but in any case, its ignored when binding to a model property (its the value of the property which determines what is selected)
Possible reason of above error could be variable fileConfigListEntries is null or not got the data from dbcontext.
As drop down list is bounded with null or collection with no elements error coming as "There is no ViewData item of type 'IEnumerable' that has the key 'FileConfigId'.."
I suggest replace fileConfigListEntries view bag data with hard-coded data and see error disappears.
I have created a View Model called CompetitionRoundModel which is partially produced below:
public class CompetitionRoundModel
{
public IEnumerable<SelectListItem> CategoryValues
{
get
{
return Enumerable
.Range(0, Categories.Count())
.Select(x => new SelectListItem
{
Value = Categories.ElementAt(x).Id.ToString(),
Text = Categories.ElementAt(x).Name
});
}
}
[Display(Name = "Category")]
public int CategoryId { get; set; }
public IEnumerable<Category> Categories { get; set; }
// Other parameters
}
I have structured the model this way because I need to populate a dropdown based on the value stored in CategoryValues. So for my view I have:
#using (Html.BeginForm())
{
<div class="form-group">
#Html.LabelFor(model => model.CategoryId, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.DropDownListFor(model => model.CategoryId, Model.CategoryValues, new { #class = "form-control" })
#Html.ValidationMessageFor(model => model.CategoryId, "", new { #class = "text-danger" })
</div>
</div>
// Other code goes here
}
I have selected model.CategoryId in the DropDownListFor() method since I want to bind the selected value to CategoryId. I really don't care for CategoryValues, I just need it to populate the DropDown.
My problem now is that when my Controller receives the values for my Model in the action method, CategoryValues is null which causes the system to throw a ArgumentNullException (the line that is highlighted is the return Enumerable line.
I have even tried [Bind(Exclude="CategoryValues")] but no change at all. Any help would be much appreciated.
Your not (and should not be) creating form controls for each property of each Category in your IEnumerable<Category> collection so in your POST method, the value of Categories is null (it never gets initialized). As soon as you attempt CategoryValues and exception is thrown by your .Range(0, Categories.Count()) line of code in the getter.
Change you view model to give CategoryValues a simple geter/setter, and delete the Categories property
public class CompetitionRoundModel
{
public IEnumerable<SelectListItem> CategoryValues { get; set; }
[Display(Name = "Category")]
public int CategoryId { get; set; }
.... // Other properties
}
and populate the SelectList in the controller methods, for example
var categories db.Categories; // your database call
CompetitionRoundModel model = new CompetitionRoundModel()
{
CategoryValues = categories.Select(x => new SelectListItem()
{
Value = x.Id.ToString(),
Text = x.Name
},
....
};
return View(model);
or alternatively
CompetitionRoundModel model = new CompetitionRoundModel()
{
CategoryValues = new SelectList(categories, "Id", "Name" ),
Note also that if you return the view (because ModelState is invalid, the you need to repopulate the value of CategoryValues (refer The ViewData item that has the key 'XXX' is of type 'System.Int32' but must be of type 'IEnumerable' for more detail)
Since CategoryValues just populates the drop down, it will never post back to the server and you'll need to rebuild the list from the database before using it in the GET or POST operation. The CategoryId property is the value that will be posted back to the server from the DropDownList.
Hi I have a problem with DropDownListFor on the Edit view.
Basically I'm using a partial view which contains my form and in my Edit and Create view I call this partial view.
I have around 5 similiar DropdownlistFor and these work well on create action but in edit doesn't, mainly i'm not getting (unable) to set the selected value.
In my Edit Action (GET), I fill my property ViewModel if the true object has the property filled.
if(icb.BAOfficer != null)
editICB.BAOfficer = icb.BAOfficer;
List<Staff> staffs = _fireService.GetAllStaffs().ToList();
staffs.Insert(0, new Staff { StaffId = -1, Name = "" });
editICB.BAOfficers = staffs;
return View(editICB);
This is how I'm filling my drop down and how I'm trying to set the selected value.
#Html.DropDownListFor(model => model.BAOfficerSelected, new SelectList(Model.BAOfficers, "StaffId", "Name", (Model.BAOfficer!= null ? Model.BAOfficer.StaffId:-1)), new { #class = "rounded indent" })
#Html.ValidationMessageFor(model => model.BAOfficer.StaffId)
I solve the problem setting a value to my model.BAOfficerSelected in Edit Action, this was the (easy) secret.
I need the first item like a empty option because is not a required information, but on the edit view if has value I need to set it as selected option.
In the end, it was my code.
My Model
public int BAOfficerSelected { get; set; }
public SelectList BAOfficers { get; set; }`
My Controller Create/Edit Action
if (icb.BAOfficer != null) // only for edit action
editICB.BAOfficerSelected = icb.BAOfficer.StaffId; //this will set the selected value like a mapping
//for Edit and Create
List<Staff> staffs = _fireService.GetAllStaffs().ToList();
staffs.Insert(0, new Staff { StaffId = -1, Name = "" });
editICB.BAOfficers = new SelectList(staffs, "StaffId", "Name");
return View(editICB);`
My View
#Html.DropDownListFor(model => model.BAOfficerSelected, Model.BAOfficers, new { #class = "rounded indent" })
I hope this can help others.
The best and cleanest way of doing this is setting the selected value in server side, in the SelectList object.
So, if your BAOfficerSelected is nullable... it is all simpler: You don't need to rely in adding a dummy item to hold the -1 for not selected value.
Instead, you do it this way:
List<Staff> staffs = _fireService.GetAllStaffs().ToList();
editICB.BAOfficers = new SelectList(staffs, "StaffId", "Name", editICB.BAOfficer != null ? editICB.BAOfficer.StaffId : null);
Of course, the BAOfficers need to be changed type from List<Staff> to SelectList.
Then, in your partial view you do:
#Html.DropDownListFor(model => model.BAOfficerSelected, Model.BAOfficers, "Select one...", new { #class = "rounded indent" })
Adding the 3rd parameter is needed to indicate that the default value (if nothing is selected) is that text.
Instead of using a SelectList, I often find it works better to use a List<SelectListItem>.
Further, I usually use an EditorTemplate for my dropdowns to keep my views clean.
So if my select list returns List<SelectListItem>:
public List<SelectListItem> BAOfficers { get; set };
You can set it up like this:
model.BAOfficers = staffs.Select(staff =>
new SelectListItem { Text = staff.Name, Value = staff.StaffId }).ToList();
Then in your EditorTemplate:
<!-- EditorTempaltes\DropDownList.cshtml -->
#model System.String
<p>
#Html.LabelFor(m => m):
#Html.DropDownListFor(m => m, new SelectList(
(List<SelectListItem>)ViewData["selectList"], "Value", "Text",
String.IsNullOrEmpty(Model) ? String.Empty : Model), String.Empty)
#Html.ValidationMessageFor(m => m)
</p>
And then in the view, just pass the SelectList into the EditorTemplate:
#Html.EditorFor(m => m.BAOfficerSelected, "DropDownList",
new { selectList = Model.BAOfficers() })
I met the same problem ,too.
According the article https://dotnetfiddle.net/PIGNLF which way gave a simple way to deal with this problem without two Models or more classes.enter link description here
here is my code
add model
public class NoteSelectLisModel
{
public string Value { get; set; }
public string Name { get; set; }
}
add Controller
public ActionResult Edit(int? _ID)
{
ViewBag.NoteState = new SelectList(new List<NoteSelectLisModel>()
{
new NoteSelectLisModel() {Value="1",Name="A)"},
new NoteSelectLisModel() {Value="2",Name="B"},
new NoteSelectLisModel() {Value ="3",Name ="C"}
}, "Value", "Name", 1);
Table ut = _db.Tables.Find(_ID);
if (ut == null)
{
return HttpNotFound();
}
else
{
return View(ut);
}
}
add View .cshtml
#Html.DropDownListFor(m => m.NOTE, (IEnumerable<SelectListItem>)ViewBag.NoteState, "No Selected")
The edit's Model is the same and the dropdownlist passed by View.bag
I'm new to MVC so this may sound silly, but here goes: I have a model that contains two lists that need to be passed to an edit form:
public class BaseViewModel
{
public IEnumerable<portal_notifications_types> Types { get; set; }
public IEnumerable<portal_notifications_importances> Importances { get; set; }
}
In the edit form, i Have two dropdownlists for this fields:
#Html.DropDownListFor(m => m.Notification.TypeId, new SelectList(Model.Types, "Id", "Type"), "-- Select type --", new { onchange = "GetNotifType();", style = "width:150px;" })
#Html.DropDownListFor(m => m.Notification.ImportanceId, new SelectList(Model.Importances, "Id", "Importance"), "-- Select importance --", new { style = "width:150px;" })
When I first enter the edit view, everything is ok, the dropdownlists are populated and the corresponding value is selected.
However, when I submit the form, the dropdownlists throw an error, because the Model.Types and Model.Importances lists are null.
How could I overcome this ? I would like to avoid using ViewBag to store those lists, although I know it would work.
Pass the View Model again in your Post Action Method.
[HttpPost]
public ActionResult Index(ViewModel m)
{
return View(m); //Pass the View Model again.
}
You have to repopulate these two SelectLists in the Controller POST method for Edit and again pass the ViewModel in the view for edit. Please share your Controller code for Edit for more details.
I have a scenario where I want to pick 3 items out of a list of checkboxes. This works fine, but if the list of checkboxes gets long, the page looks unwieldy. So I wanted to change it to 3 dropdown lists. so the page was a lot smaller, but none of the dropdown lists honor the selected value.
So I tried code like this
#Html.DropDownListFor(model => model.CheckedLarcenyTypes, new SelectList(Model.LarcenyTypes, "Key", "Value", Model.CheckedLarcenyTypes.Length > 0 ? Model.CheckedLarcenyTypes[0] : null as Int32?), String.Empty, new { id = "Larceny1" })
#Html.DropDownListFor(model => model.CheckedLarcenyTypes, new SelectList(Model.LarcenyTypes, "Key", "Value", Model.CheckedLarcenyTypes.Length > 1 ? Model.CheckedLarcenyTypes[1] : null as Int32?), String.Empty, new { id = "Larceny2" })
#Html.DropDownListFor(model => model.CheckedLarcenyTypes, new SelectList(Model.LarcenyTypes, "Key", "Value", Model.CheckedLarcenyTypes.Length > 2 ? Model.CheckedLarcenyTypes[2] : null as Int32?), String.Empty, new { id = "Larceny3" })
Now the dropdowns are created correctly and the correct value is getting bound and on a POST I see the values getting sent back in the view model.
I just can't get the selectvalue to show in the dropdown. upon re-loading the page, the dropdowns are still just blank.
What am I doing wrong here? Is this even possible?
Your problem is related to what's described here.
Reading the Selection
If you are using the same model to accept input from the edit view
during a postback, you might think the default model binder will
repopulate the Albums collection with all the album information and
set the selected album. Unfortunately - the web doesn’t work this way
and the Albums collection will be empty.
So you must have a ViewModel like this:
public class LarcenyViewModel
{
public int CheckedLarcenyType1 { get; set; }
public int CheckedLarcenyType2 { get; set; }
public int CheckedLarcenyType3 { get; set; }
public IEnumerable<SelectListItem> LarcenyTypes { get; set; }
}
Populate the ViewModel like this:
LarcenyViewModel larcenyViewModel = new LarcenyViewModel();
// Use a database, enum or whatever to get the LarcenyTypes... :)
larcenyViewModel.LarcenyTypes = new SelectList(
database.FindAllLarcenyTypes(), "LarcenyId", "Name");
View code:
#Html.DropDownListFor(model => model.CheckedLarcenyType1, Model.LarcenyTypes, String.Empty, new { id = "Larceny1" })
#Html.DropDownListFor(model => model.CheckedLarcenyType2, Model.LarcenyTypes, String.Empty, new { id = "Larceny2" })
#Html.DropDownListFor(model => model.CheckedLarcenyType3, Model.LarcenyTypes, String.Empty, new { id = "Larceny3" })