DropDownListFor() bindling value AND text to viewmodel - asp.net-mvc

I have a form on a View with a dropdown list, implemented with DropDownListFor(). This View is strongly typed to a ViewModel, which has a SelectList property to hold the options of the dropdown, and then another property to hold the selected value of the dropdown. This is working fine, but what I'd like to do is, hold both the selected value AND selected text of the dropdown in my second property. The reason I want to do this is so that as the form selfposts, I have both the text and value of each selection.
I tried changing the selected value property from an int to a KeyValuePair but only the int part of the pair is set on form submission.
Perhaps there is a better way altogether to accomplish this, I am open to all suggestions including a partial redesign of my methods.
Controller (building SelectList)
SelectList leadTypeGroups = new SelectList(_enrollmentRepository.GetLeadTypeGroups(), "Key", "Value");
ViewModel
public KeyValuePair<int, string> LeadTypeGroupID { get; set; }
public SelectList LeadTypeGroups { get; set; }
View
#Html.DropDownListFor(selected => Model.LeadTypeGroupID, Model.LeadTypeGroups, " ")

Have the sever pull the values from the database (or an in-memory cache) on each request. Alternatively, have a hidden field with javascript that updates it with the appropriate text whenever the dropdown selection changes.

Change the ViewModel to a List and then use a for loop to spit out a drop down for each item in the list. Something like...
View
#for( int i = 0; i < Model.LeadTypeGroupIDs; i++ )
{
#Html.DropDownListFor(x => Model.LeadTypeGroupIDs[i], Model.LeadTypeGroups, " ")
}
ViewModel
public List<string> LeadTypeGroupIDs { get; set; }
public SelectList LeadTypeGroups { get; set; }

Related

Show dropdownlist in the View

I am working on a project in which, i am getting the client names from database table using the HomeController>Index Action method.
I want to send this list to Index view and display this list in the dropdownlist.
Request you to please help me with the View accordingly as i am new to MVC.
Home Controller
public ActionResult Index()
{
var model = from c in
_mdlCntxtcls.clients
where (DateTime.Now<=c.End_Date)
select c;
return View(model);
}
Model
public class Client
{
public int ClientID { get; set; }
public string Client_Names { get; set; }
public DateTime Start_Date { get; set; }
public DateTime End_Date { get; set; }
}
Please help as early as possible
Thank you
You are passing a collection of Client objects to the view. So your view should be strongly typed to a collection of Client object to accept that as the (view) model data.
You can use the DropDownList html helper method to render a SELECT element from this view model data. You can create a SelectList object from this collection (your page model)
#model IEnumerable<YourNamespaceHere.Client>
#Html.DropDownList("StudentSelect",new SelectList(Model,"ClientID","Client_Names"))
This will render a SELECT element with name attribute value set to StudentSelect. Each options in the SELECT elemtn will have the ClientID as the value attribute value and Client_Names property value as the option text.
You can also use viewbag or viewdata for send list of Client from controller to view and then you can put it in dropdown list.
In Controller you can use like :
List<SelectListItem> ClientList = new List<SelectListItem>();
using (dbContext db = new dbContext())
{
var Clients = db.Client.ToList();
foreach (var i in Clients)
{
ClientList.Add(new SelectListItem { Text = i.Client_Name, Value = i.ClientID.ToString() });
}
}
ViewBag.ClientList = ClientList;
and in view side you can use that viewbag like :
#Html.DropDownListFor(x => x.Client, (IEnumerable<SelectListItem>)ViewBag.ClistList)

ASP.NET MVC 5 site - edit view not selecting item in DropDownListFor

I have an MVC 5 site...
A story can be optionally associated with a PlaceId. A blank placeId is also valid. A place can be associated with more than one story.
Models
public class Place
{
public Guid Id { get; set; }
public string PlaceName { get; set; }
}
public class Story
{
public Guid Id { get; set; }
public Guid? PlaceId { get; set; }
public string StoryName { get; set; }
}
I have several requirements.
When editing the story I would like a drop down list of all places to
be displayed - with the associated place (if any) - selected.
I want to use the strongly typed DropDownListFOR (as opposed to
DropDownList).
I want to add a "No Associated Place" which will be
selected if PlaceId is null (and should pass null back to the model).
I want to add a css class = "form-control" to the DropDownListFor.
Controller (Get)
public ActionResult Edit(Guid Id)
{
// Get Story
var story = StoryRepo.SelectArticle(Id);
// Put select list of all places in ViewBag
ViewBag.PlaceId = new SelectList(PlaceRepo.SelectAll(), "Id", "PlaceName", new { Id = story.PlaceId });
// Return view
return View(story);
}
In View
#Html.DropDownListFor(x => x.PlaceId, (IEnumerable<SelectListItem>)ViewBag.PlaceId, "No Associated Place",
new { #class = "form-control" })
This populates the dropdown list fine, and when you select an item the PlaceId is in the model bound to the controller. However - it does not select the existing PlaceId when the view loads.
Shouldn't the final parameter in the ViewBag.PlaceId line new { Id = story.PlaceId } - cause this selection?
I can't find anything on this specific issue online - and can find little about how to bind a dropdown to a strongly typed edit view in the way I require.
How can I make it select the correct item? (also any improvements on how I am doing this also appreciated).
Thanks.
I think you need to change the following code
// Put select list of all places in ViewBag
ViewBag.PlaceId = new SelectList(PlaceRepo.SelectAll(), "Id",
"PlaceName", new { Id = story.PlaceId });
to become
// Put select list of all places in ViewBag
ViewBag.PlaceId = new SelectList(PlaceRepo.SelectAll(), "Id",
"PlaceName", story.PlaceId);
Definition of the SelectedList from msdn
SelectList(IEnumerable, String, String, Object): Initializes a new
instance of the SelectList class by using the specified items for the
list, the data value field, the data text field, and a selected value.
here a working demo
updated demo
Hope this will help you

Multiple Dropdown Lists, Multiple Models

I have a few entities that I want to fill into a few dropdown lists on a single form. Which is the best way to go about doing so. For multiple models in a single view I've created a viewmodel and threw the entities into it but how can I bring back the list in the database say for entity "Network" and fill the dropdown with "Name" and "NetworkID"?
First create the Model:
public class Data
{
public List<tbl_Dept> lstDepatrment;
public List<tbl_employees> lstEmployee;
//other
}
Then just Create a View
#model MVCApp.Models.Data
#{
var categoryList = Model.lstDepatrment.Select(cl => new SelectListItem
{
Value = cl.Dept_ID.ToString(),
Text = cl.Dept_Description == null ? String.Empty : cl.Dept_Description
});
//list for other Drop Down
}
#(Html.DropDownList("sampleDropdown", categoryList, "-----Select-----"))
You can do as follows:
Designing your model:
Prepare Select List for as many dropdowns you want
For eg:
Public class ModelName
{
...// Properties
public IEnumerable<SelectListItem> ListName1 { get; set; }
public IEnumerable<SelectListItem> ListName2 { get; set; }
public IEnumerable<SelectListItem> NetWorkList { get; set; }
... //etc
}
Prepare and bind List to Model in Controller :
public ActionResult Index(ModelName model)
{
var networks = // Your network List
model.NetWorkList = networks.Select(x=> new SelectListItem() {
Text = x.Name,
Value = x.NetworkID
});
..// Same as above prepare the list for other dropdowns
return View(model);
}
Then in your view prepare your dropdown as follows:
#Html.DropDownListFor(m => Model.NetworkID,Model.NetWorkList)
Well in that case you can keep all the model list data in somewhere in java script model and then using the JQuery you can bind all of Dropdown controls with same model list.
Alternatively you can fetch that data using Ajax and bind those Dropdowns there in java script and retrieve the value rather then throwing data multiple list from controller.

ASP.NET MVC - How to keep collections value when calls an Action?

I have a ViewModel like this:
public class MyViewModel
{
public string SelectedItem { get; set; }
public List<MyClass> Items { get; set; }
}
I fill these items on screen with a #Html.DropDownListFor(m => m.SelectedItem, new SelectList(...)).
Ok, but when I call any action which receives this ViewModel, I got this collection empty.
Is there a way to get back the DropDownList values when I call any action?
That's a normal behavior and it's how HTML works. Only the selected value of a <select> element is sent to the server, not the entire collection. In your POST action if you want to retrieve the collection all you have to do is exactly the same you did in your GET action to retrieve it in the first place. That's usually a database call. And if you are afraid that you might be hitting your database quite often, just cache the collection.
In a tag form you can only send the value selected in the tag select, in this case the value of SelectedItem.
If you need also send the list of values ​​of Items, you have to create something like this:
#{
var ind = 0;
foreach(var item in Model.Items)
{
<input type="hidden" name="Items[#ind].Id" value="#item.Id"/>
ind++;
}
}
But id you can send the data by Ajax, in this case is mode simple, because you can create the data to send. See this plugin toDictionary
One way is to have the List<SelectListItem> as part of the view model and populate it via a method called from the controller and pass it to the view, e.g.
View model:
public List<SelectListItem> SelectList { get; set; }
And in the view:
#Html.DropDownListFor(model => model.SelectedItem, Model.SelectList)

ASP.NET MVC Html.DropDownList SelectedValue

I have tried this is RC1 and then upgraded to RC2 which did not resolve the issue.
// in my controller
ViewData["UserId"] = new SelectList(
users,
"UserId",
"DisplayName",
selectedUserId.Value); // this has a value
result: the SelectedValue property is set on the object
// in my view
<%=Html.DropDownList("UserId", (SelectList)ViewData["UserId"])%>
result: all expected options are rendered to the client, but the selected attribute is not set. The item in SelectedValue exists within the list, but the first item in the list is always defaulted to selected.
How should I be doing this?
Update
Thanks to John Feminella's reply I found out what the issue is. "UserId" is a property in the Model my View is strongly typed to. When Html.DropDownList("UserId" is changed to any other name but "UserId", the selected value is rendered correctly.
This results in the value not being bound to the model though.
This is how I fixed this problem:
I had the following:
Controller:
ViewData["DealerTypes"] = Helper.SetSelectedValue(listOfValues, selectedValue) ;
View
<%=Html.DropDownList("DealerTypes", ViewData["DealerTypes"] as SelectList)%>
Changed by the following:
View
<%=Html.DropDownList("DealerTypesDD", ViewData["DealerTypes"] as SelectList)%>
It appears that the DropDown must not have the same name has the ViewData name :S weird but it worked.
Try this:
public class Person {
public int Id { get; set; }
public string Name { get; set; }
}
And then:
var list = new[] {
new Person { Id = 1, Name = "Name1" },
new Person { Id = 2, Name = "Name2" },
new Person { Id = 3, Name = "Name3" }
};
var selectList = new SelectList(list, "Id", "Name", 2);
ViewData["People"] = selectList;
Html.DropDownList("PeopleClass", (SelectList)ViewData["People"])
With MVC RC2, I get:
<select id="PeopleClass" name="PeopleClass">
<option value="1">Name1</option>
<option selected="selected" value="2">Name2</option>
<option value="3">Name3</option>
</select>
You can still name the DropDown as "UserId" and still have model binding working correctly for you.
The only requirement for this to work is that the ViewData key that contains the SelectList does not have the same name as the Model property that you want to bind. In your specific case this would be:
// in my controller
ViewData["Users"] = new SelectList(
users,
"UserId",
"DisplayName",
selectedUserId.Value); // this has a value
// in my view
<%=Html.DropDownList("UserId", (SelectList)ViewData["Users"])%>
This will produce a select element that is named UserId, which has the same name as the UserId property in your model and therefore the model binder will set it with the value selected in the html's select element generated by the Html.DropDownList helper.
I'm not sure why that particular Html.DropDownList constructor won't select the value specified in the SelectList when you put the select list in the ViewData with a key equal to the property name. I suspect it has something to do with how the DropDownList helper is used in other scenarios, where the convention is that you do have a SelectList in the ViewData with the same name as the property in your model. This will work correctly:
// in my controller
ViewData["UserId"] = new SelectList(
users,
"UserId",
"DisplayName",
selectedUserId.Value); // this has a value
// in my view
<%=Html.DropDownList("UserId")%>
The code in the previous MVC 3 post does not work but it is a good start. I will fix it. I have tested this code and it works in MVC 3 Razor C# This code uses the ViewModel pattern to populate a property that returns a List<SelectListItem>.
The Model class
public class Product
{
public string Name { get; set; }
public decimal Price { get; set; }
}
The ViewModel class
using System.Web.Mvc;
public class ProductListviewModel
{
public List<SelectListItem> Products { get; set; }
}
The Controller Method
public ViewResult List()
{
var productList = new List<SelectListItem>();
foreach (Product p in Products)
{
productList.Add(new SelectListItem
{
Value = p.ProductId.ToString(),
Text = "Product: " + p.Name + " " + p.Price.ToString(),
// To set the selected item use the following code
// Note: you should not set every item to selected
Selected = true
});
}
ProductListViewModel productListVM = new ProductListViewModeld();
productListVM.Products = productList;
return View(productListVM);
}
The view
#model MvcApp.ViewModels.ProductListViewModel
#using (Html.BeginForm())
{
#Html.DropDownList("Products", Model.Products)
}
The HTML output will be something like
<select id="Products" name="Products">
<option value="3">Product: Widget 10.00</option>
<option value="4">Product: Gadget 5.95</option>
</select>
depending on how you format the output. I hope this helps. The code does work.
If we don't think this is a bug the team should fix, at lease MSDN should improve the document. The confusing really comes from the poor document of this. In MSDN, it explains the parameters name as,
Type: System.String
The name of the form field to return.
This just means the final html it generates will use that parameter as the name of the select input. But, it actually means more than that.
I guess the designer assumes that user will use a view model to display the dropdownlist, also will use post back to the same view model. But in a lot cases, we don't really follow that assumption.
Use the example above,
public class Person {
public int Id { get; set; }
public string Name { get; set; }
}
If we follow the assumption,we should define a view model for this dropdownlist related view
public class PersonsSelectViewModel{
public string SelectedPersonId,
public List<SelectListItem> Persons;
}
Because when post back, only the selected value will post back, so it assume it should post back to the model's property SelectedPersonId, which means Html.DropDownList's first parameter name should be 'SelectedPersonId'. So, the designer thinks that when display the model view in the view, the model's property SelectedPersonId should hold the default value of that dropdown list. Even thought your List<SelectListItem> Persons already set the Selected flag to indicate which one is selected/default, the tml.DropDownList will actually ignore that and rebuild it's own IEnumerable<SelectListItem> and set the default/selected item based on the name.
Here is the code from asp.net mvc
private static MvcHtmlString SelectInternal(this HtmlHelper htmlHelper, ModelMetadata metadata,
string optionLabel, string name, IEnumerable<SelectListItem> selectList, bool allowMultiple,
IDictionary<string, object> htmlAttributes)
{
...
bool usedViewData = false;
// If we got a null selectList, try to use ViewData to get the list of items.
if (selectList == null)
{
selectList = htmlHelper.GetSelectData(name);
usedViewData = true;
}
object defaultValue = (allowMultiple) ? htmlHelper.GetModelStateValue(fullName, typeof(string[])) : htmlHelper.GetModelStateValue(fullName, typeof(string));
// If we haven't already used ViewData to get the entire list of items then we need to
// use the ViewData-supplied value before using the parameter-supplied value.
if (defaultValue == null && !String.IsNullOrEmpty(name))
{
if (!usedViewData)
{
defaultValue = htmlHelper.ViewData.Eval(name);
}
else if (metadata != null)
{
defaultValue = metadata.Model;
}
}
if (defaultValue != null)
{
selectList = GetSelectListWithDefaultValue(selectList, defaultValue, allowMultiple);
}
...
return tagBuilder.ToMvcHtmlString(TagRenderMode.Normal);
}
So, the code actually went further, it not only try to look up the name in the model, but also in the viewdata, as soon as it finds one, it will rebuild the selectList and ignore your original Selected.
The problem is, in a lot of cases, we don't really use it that way. we just want to throw in a selectList with one/multiple item(s) Selected set true.
Of course the solution is simple, use a name that not in the model nor in the viewdata. When it can not find a match, it will use the original selectList and the original Selected will take affect.
But i still think mvc should improve it by add one more condition
if ((defaultValue != null) && (!selectList.Any(i=>i.Selected)))
{
selectList = GetSelectListWithDefaultValue(selectList, defaultValue, allowMultiple);
}
Because, if the original selectList has already had one Selected, why would you ignore that?
Just my thoughts.
This appears to be a bug in the SelectExtensions class as it will only check the ViewData rather than the model for the selected item. So the trick is to copy the selected item from the model into the ViewData collection under the name of the property.
This is taken from the answer I gave on the MVC forums, I also have a more complete answer in a blog post that uses Kazi's DropDownList attribute...
Given a model
public class ArticleType
{
public Guid Id { get; set; }
public string Description { get; set; }
}
public class Article
{
public Guid Id { get; set; }
public string Name { get; set; }
public ArticleType { get; set; }
}
and a basic view model of
public class ArticleModel
{
public Guid Id { get; set; }
public string Name { get; set; }
[UIHint("DropDownList")]
public Guid ArticleType { get; set; }
}
Then we write a DropDownList editor template as follows..
<%# Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %>
<script runat="server">
IEnumerable<SelectListItem> GetSelectList()
{
var metaData = ViewData.ModelMetadata;
if (metaData == null)
{
return null;
}
var selected = Model is SelectListItem ? ((SelectListItem) Model).Value : Model.ToString();
ViewData[metaData.PropertyName] = selected;
var key = metaData.PropertyName + "List";
return (IEnumerable<SelectListItem>)ViewData[key];
}
</script>
<%= Html.DropDownList(null, GetSelectList()) %>
This will also work if you change ArticleType in the view model to a SelectListItem, though you do have to implement a type converter as per Kazi's blog and register it to force the binder to treat this as a simple type.
In your controller we then have...
public ArticleController
{
...
public ActionResult Edit(int id)
{
var entity = repository.FindOne<Article>(id);
var model = builder.Convert<ArticleModel>(entity);
var types = repository.FindAll<ArticleTypes>();
ViewData["ArticleTypeList"] = builder.Convert<SelectListItem>(types);
return VIew(model);
}
...
}
The problems is that dropboxes don't work the same as listboxes, at least the way ASP.NET MVC2 design expects: A dropbox allows only zero or one values, as listboxes can have a multiple value selection. So, being strict with HTML, that value shouldn't be in the option list as "selected" flag, but in the input itself.
See the following example:
<select id="combo" name="combo" value="id2">
<option value="id1">This is option 1</option>
<option value="id2" selected="selected">This is option 2</option>
<option value="id3">This is option 3</option>
</select>
<select id="listbox" name="listbox" multiple>
<option value="id1">This is option 1</option>
<option value="id2" selected="selected">This is option 2</option>
<option value="id3">This is option 3</option>
</select>
The combo has the option selected, but also has its value attribute set. So, if you want ASP.NET MVC2 to render a dropbox and also have a specific value selected (i.e., default values, etc.), you should give it a value in the rendering, like this:
// in my view
<%=Html.DropDownList("UserId", selectListItems /* (SelectList)ViewData["UserId"]*/, new { #Value = selectedUser.Id } /* Your selected value as an additional HTML attribute */)%>
In ASP.NET MVC 3 you can simply add your list to ViewData...
var options = new List<SelectListItem>();
options.Add(new SelectListItem { Value = "1", Text = "1" });
options.Add(new SelectListItem { Value = "2", Text = "2" });
options.Add(new SelectListItem { Value = "3", Text = "3", Selected = true });
ViewData["options"] = options;
...and then reference it by name in your razor view...
#Html.DropDownList("options")
You don't have to manually "use" the list in the DropDownList call. Doing it this way correctly set the selected value for me too.
Disclaimer:
Haven't tried this with the web forms view engine, but it should work too.
I haven't tested this in the v1 and v2, but it might work.
I managed to get the desired result, but with a slightly different approach. In the Dropdownlist i used the Model and then referenced it. Not sure if this was what you were looking for.
#Html.DropDownList("Example", new SelectList(Model.FeeStructures, "Id", "NameOfFeeStructure", Model.Matters.FeeStructures))
Model.Matters.FeeStructures in above is my id, which could be your value of the item that should be selected.

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