MVC Custom ViewModel and auto binding

Question

I have a custom ViewModel defined as :

public class SampleFormViewModel
{
    public SampleFormViewModel(SelectList companies, Widget widget)
    {
        Compa         


        

Answer 1

You need to have a parameterless constructor and I believe that the properties need to have public setters. The default binder creates the object using a constructor that takes no parameters, then uses reflection on the public properties to set values from the form/query parameters.

public class SampleFormViewModel
{
    public SampleFormViewModel() { }

    public SelectList Companies { get; set; }
    public Widget Widget { get; set; }
}

I suspect, though, that what you really want to do is not get the view model, but the underlying Widget model and select list value on form post. I don't think the binder will be able to reconstruct a SelectList on post since it only has the selected value in the parameters.

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit( int CompanyID, Widget widget )
{
}