在视图中创建新的SelectList时未设置DropDownListFor值

Question

Example #1 (this one works)

@Html.DropDownListFor(m => m.State.Id, Model.States)

I'm creating the SelectList in the controller for the first example like this.

var states = Repository.GetStates();
var statesSelectList = new SelectList(states, "Id", "Name");

//model.States is a SelectList
model.States = statesSelectList;

Example #2 (this doesn't set the selected value on load)

@Html.DropDownListFor(m => m.State.Id, new SelectList(Model.States, "Id", "Name"))

I'm creating the SelectList in the view for the second example, and the controller looks like this.

//model.States is a List<State>.
model.States = Repository.GetStates();

It seems there must be something simple that I'm missing. Let me know if I need to clarify anything else. Thanks.

Answer 1

Add a property to your view model:

private int? stateId;
public int StateId
{
    get { return stateId ?? State.Id; }
    set { stateId = value; }
}

Then in your Razor view:

@Html.DropDownListFor(m => m.StateId, new SelectList(Model.States, "Id", "Name"))

And finally in your controller POST action:

model.State = Repository.GetState(model.StateId);

Answer 2

Simple, yes. Obvious no. DropDownListFor does not bind to nested objects like m => m.State.Id .

It is designed for more basic relationships like m => m.Id