Question

So I’m trying to get a common dropdown list of event types in MVC.

I’ve created a partial view under Shared/EditorTemplates/

Here’s its content:

@model EventManager.Models.CreateEventModel

@{

    EventManager.Models.DropdownEventTypesModel dropdownList = new EventManager.Models.DropdownEventTypesModel();

    List<SelectListItem> types = dropdownList.EventTypes;

    Html.DropDownListFor(model => model.Type, types);

}

This works great, except for the fact that I would need to create a new partial view for every model that wants to use this common dropdown, defeating the purpose. Is there a way in C# MVC to say that the model will have this Type property, but not specify a specific model that it will come from?

I tried @model dynamic, but it returned this error in Visual Studio:

An expression tree may not contain a dynamic operation

Answer 1

All you need to do is make the model type of your editor template partial the type of the property that this editor is going to be editing, not the type of the containing model.

Suppose you have an EventType class, a CreateEventModel and an EditEventModel, and both the CreateEventModel and the EditEventModel have EventType properties, like this:

public class CreateEventModel
{
    //Other stuff here....
    public EventType TypeToCreate { get; set; }
}

public class EditEventModel
{
    //Other stuff here....
    public EventType TypeToEdit { get; set; }
}

You create a partial in the EditorTemplates folder named EventType.cshtml, and in it you put something like this:

@model EventManager.Models.EventType

@{
    var types = //put whatever you need here to get the list of available types*;
}

@Html.DropDownListFor(m => m, types)

Notice the simple m => m expression in the DropDownListFor() call, and the fact that there’s no reference to any containing model here: the type in the @model declaration is simply EventType. All the editor template needs to know is that it is going to be used for editing properties of type EventType.

You can make use of this template in the views for your CreateEventModel and an EditEventModel as follows:

Create view:

@model EventManager.Models.CreateEventModel

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>

@*Other stuff here...*@

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

Edit view:

@model EventManager.Models.EditEventModel

@{
    ViewBag.Title = "Edit";
}

<h2>Edit</h2>

@*Other stuff here...*@

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

(*The code you use for this:

EventManager.Models.DropdownEventTypesModel dropdownList = new EventManager.Models.DropdownEventTypesModel();

List<SelectListItem> types = dropdownList.EventTypes;

doesn’t really belong in a view, but that’s another issue.)