Asp.net MVC 3 "parameter conversion from type 'System.String' to type failed" when using SelectList Dropdown box - asp.net

Question

I'm stuck and after looking this up for hours, I think I need more eyeballs.
The situation is the following:
It's an Asp.Net MVC3 with Entity Framework 4 project. And I have two classes. One ConfigurationFile and another one Action. There is a one-to-many relationship between the two. Here is a simplified view on the code:
public class ConfigurationFile
{
[Key, Required]
[Column(TypeName = "uniqueidentifier")]
public Guid Id { get; set; }
[Required]
public string Name { get; set; }
[Column(TypeName = "uniqueidentifier")]
[Required]
public Guid ActionId { get; set; }
public virtual Models.Action Action { get; set; }
}
public class Action
{
[Key, Required]
[Column(TypeName = "uniqueidentifier")]
public Guid Id { get; set; }
[Required]
public string ActionValue { get; set; }
}
Then I want to create a new ConfigurationFile, and are my two controller methods (and at this point, this is 95% Visual Studio 10 generated code):
// db is my context class.
//
// GET: /Configuration/Create
public ActionResult Create()
{
ViewBag.ActionId = new SelectList(db.Actions, "Id", "ActionValue");
return View();
}
//
// POST: /Configuration/Create
[HttpPost]
public ActionResult Create(Models.ConfigurationFile configurationfile)
{
if (ModelState.IsValid)
{
configurationfile.Id = Guid.NewGuid();
db.ConfigurationFiles.Add(configurationfile);
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.ActionId = new SelectList(db.Actions, "Id", "ActionValue", configurationfile.ActionId);
return View(configurationfile);
}
And here is a snippet of my Create view:
#model MyProject.Areas.ConfigurationFile.Models.ConfigurationFile
#using (Html.BeginForm()) {
#Html.ValidationSummary(true)
<fieldset>
<legend>Configuration File</legend>
<div class="editor-label">
#Html.LabelFor(model => model.Name)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.Name)
#Html.ValidationMessageFor(model => model.Name)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.ActionId, "Action")
</div>
<div class="editor-field">
#Html.DropDownList("ActionId", String.Empty)
#Html.ValidationMessageFor(model => model.ActionId)
</div>
<p>
<input type="submit" value="Create" />
</p>
</fieldset>
}
When I open the Create page, I can clearly see that my dropdown for the Action class is fine (correct value -- the Action.Id -- and text -- Action.ActionValue -- ) but when I submit the form, I have the following error: "The parameter conversion from type 'System.String' to type 'MyProject.Models.Action' failed because no type converter can convert between these types."
Help please !!

Answer 1

Right now MVC has no way of connecting your dropdownlist from your view to the ActionId of your ConfigurationFile object.
I would try replacing this line:
#Html.DropDownList("ActionId", String.Empty)
for this
#Html.DropDownListFor(model => model.ActionId, ViewBag.ActionId)
Other than that, I can't think of what else you might have done wrong.
I hope that helps!

Answer 2

This is how I did to circumvent the problem. I just changed my controller this way:
Models.Action act = db.Actions.Find(configurationfile.ActionId);
ModelState.Clear();
configurationfile.Action = act;
TryValidateModel(configurationfile);
And after that, the validation was Ok. A bit hacky (and another possible hit on the DB), but at least, I can keep going.