EditorFor ICollection and named Template

Question

i am new to MVC 5 and ASP.NET, EF6 and now i have a Problem with a named EditorTemplate.

My Model looks like this:

public partial class Product
{
    public int pid { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Filter> Filters{ get; set; }
}

public partial class Filter
{
    public bool isRemoveable { get; set; }
}

And i have a EditorTemplate called FiltersCustomEditor, thats look like this:

@model IList<Filter>

@Html.EditorFor(modelItem => @Model[i].isRemoveable)

My Problem is now that in my Product View i can´t call:

@Html.EditorFor(m => m.Filters, "FiltersCustomEditor")

I get this error:

The model element that has been passed to the dictionary , is of type "System.Collections.Generic.HashSet 1[Filter]". However, this dictionary requires a model item of type "System.Collections.Generic.IList 1[Filter]". However, this dictionary requires a model item of type "System.Collections.Generic.IList 1[Filter]".]

So i tried to call it like this:

@Html.EditorFor(m => m.Filters.ToList(), "FiltersCustomEditor")

And get this error:

Templates can only be used with field access , property access , one-dimensional array indices or custom Indexerausdrücken with a single parameter .

If i convert the ICollection in my Model to a List it works perfect. But this is a generated class from Entity Framework so a change here breaks the EF functionality.

I think this is a special problem for named Templates. Because if i make a Default EditorTemplate for a Single Filter called Filter.cshtml and calling

@Html.EditorFor(m => m.Filters)

The ICollection is handled internaly very well and the EditorFor calls the Template for each Object in the List.

But their must be a solution for this Problem. The Only thing that works is to change the Template to

@model ICollection<Filter>

@Html.EditorFor(modelItem => @Model.ToList()[i].isRemoveable)

And call it like this

 @Html.EditorFor(m => m.Filters, "FiltersCustomEditor")

But i think this is realy a weak solution, specialy for performance, if every field must convert the ICollection to a List before access.

So is their a way to workaround or am i missing something?

Answer 1

Your passing ICollection<Filter> to the template, but the model in the template is IList<Filter> , hence the error ( ICollection<T> is not IList<T> ). However your approach is not correct. The EditorFor() method accepts IEnumerable<T> so the code can be simplified to

In /Views/Shared/EditorTemplates/Filter.cshtml (note the template must be named the same as the name of the class)

@model yourAssembly.Filter
@Html.CheckBoxFor(m => m.isRemoveable)
.... // add any other properties, labels etc of Filter

and then in the main view it is simply

@model yourAssembly.Product
@using (Html.BeginForm())
{
  ....
  @Html.EditorFor(m => m.Filters)
}

The EditorFor() method will correctly generate the html for each item in your collection based on the template (no loops, no passing collections etc.)

Side note: Further to you comments, you can also place specific EditorTemplates related to each controller in the /Views/YourControllerName/EditorTemplates folder. By default, the EditorFor() method will first search /Views/YourController/EditorTemplates . If one is not found it will then search /Views/Shared/EditorTemplates . And finally if one is not found it will use the built in default template(s) based on your model properties.