Question

I have been wrestling with what should be a very simple thing for weeks now. I simply want to create a dropdownlist in asp.net mvc 3 razor html page and I want the data for the dropdownlist to come from a model.

My Model is as follows which is in the Models.Project namespace.

public class Project
{
    public Project()
    {
        CategoryId = 0;
        Name = "";
        Description = "";
        //Categories = new Dictionary<int, string>();

        Entities _db = new Entities(); //ef4
        CateogoriesList = from c in _db.Categories 
                        orderby c.Name
                        select c.Name;
    }

    public int CategoryId { get; set; }

    [Required]
    [DataType(DataType.Text)]
    [Display(Name = "Project Name")]
    public string Name { get; set; }

    [Required]
    [DataType(DataType.MultilineText)]
    [Display(Name = "Project Description")]
    public string Description { get; set; }

    public IQueryable<string> CateogoriesList;

}

My Controller action is as follows

public ActionResult Create()
{
    Models.Project.Project proj = new Models.Project.Project();
    return View(proj);
}

My Razor view has the following relevant code …

@{
    ViewBag.Title = "Create";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

@model Models.Project.Project


@using (Html.BeginForm())
{
    @Html.ValidationSummary(true);

    <fieldset>
        <legend>Submit Your Request</legend>
        <div class="editor-label">@Html.LabelFor( Model => Model.CateogoriesList  )</div>
        <div class="editor-field">
            @Html.DropDownList("Category", new SelectList( Model.CateogoriesList ) )
        </div>
    </fieldset>
    <p><input type="submit" value="Send for RFP" /></p>
}

The problem is that I get the following error …

Compiler Error Message: CS0135: 'Model' conflicts with the declaration 'System.Web.Mvc.WebViewPage<TModel>.Model'

I saw the following clip make it work with the ViewBag … and I don’t understand why it won’t work when I include the list in the model.

http://www.pluralsight-training.net/microsoft/players/PSODPlayer.aspx?author=scott-allen&name=mvc3-building-data-i&mode=live&clip=0&course=aspdotnet-mvc3-intro

I have also seen that there are a lot of people that seem to have trouble with this simple task but in my googling … I haven’t come across anyone with the same error in trying to create a drop down list.

I would appreciate any suggestions that you or anyone may have. The only thing that I’ve come up with is that the SelectList constructor takes a parameter of type System.Collections.IEnumerable and what I’m trying to pass it is System.Collections.Generic.IEnumerable … or something close to it … and I don’t know how to cast it appropriately … though I don’t think I should have to … if it works with a viewbag as the means of transportation why doesn’t it work with the model as the means of transportation?

Thanks,

EDIT:======================

The problem was to do with the type of object the selectList constructor would accept. For some reason it wouldn’t accept a generic IQueryable but when I cast the result from the entity framework using the cast extension method toArray it suddenly worked.

So my model becomes …

public class Project
{
public Project()
{

    Riebro.RiebroEntities _db = new Riebro.RiebroEntities();
    CategoriesList = (from c in _db.Categories 
                    orderby c.Name
                    select c.Name).ToArray<string>();
}


[Display(Name = "Choose a category")]
public string[] CategoriesList;

}

note the .ToArray on the end of the query and then suddenly

@Html.DropDownList("Category", new SelectList(Model.CategoriesList))

works. Though I am going to point out the Model keyword here seems to be required.

Answer 1

See your code, what’s that? that’s the reason cause the error.

  <div class="editor-label">@Html.LabelFor( Model => Model.CateogoriesList  )</div>

correct one

      <div class="editor-label">@Html.LabelFor( Model => Model.CategoryId  )</div>

@using (Html.BeginForm())
{
@Html.ValidationSummary(true);

<fieldset>
    <legend>Submit Your Request</legend>
    <div class="editor-label">@Html.LabelFor(x=>x.CategoryId )</div>
    <div class="editor-field">
        @Html.DropDownList("Category", new SelectList(Model.CateogoriesList) )            
    </div>
</fieldset>
<p><input type="submit" value="Send for RFP" /></p>
}

Here is my simulation of your entity. I just add another CategoriesList2 which use to simulate the IQueryable object, but it’s still working.

    public class Project {
    public Project() {
        CategoryId = 0;
        Name = "";
        Description = "";
        //Categories = new Dictionary<int, string>();

        //Entities _db = new Entities(); //ef4
        //CateogoriesList = from c in _db.Categories
        //                  orderby c.Name
        //                  select c.Name;
        //IQueryable<string> categoriesList = (new string[] { }).AsQueryable();
        CateogoriesList = new string[] { "abc", "def", "hij", "klm" };
        CategoriesList2 = (new string[] { "abc", "def", "hij", "klm" }).AsQueryable();
    }

    public int CategoryId { get; set; }

    [Required]
    [DataType(DataType.Text)]
    [Display(Name = "Project Name")]
    public string Name { get; set; }

    [Required]
    [DataType(DataType.MultilineText)]
    [Display(Name = "Project Description")]
    public string Description { get; set; }

    public string[] CateogoriesList;

    public IQueryable<string> CategoriesList2;

}

Here is the view by using the IQueryable categories list

@model MvcApplication3.Models.Project


@using (Html.BeginForm())
{
  @Html.ValidationSummary(true);

  <fieldset>
    <legend>Submit Your Request</legend>
    <div class="editor-label">@Html.LabelFor(x=>x.CategoryId )</div>
    <div class="editor-field">
        @Html.DropDownList("Category", new SelectList(Model.CategoriesList2) )            
    </div>
  </fieldset>
  <p><input type="submit" value="Send for RFP" /></p>
}