Advance Binding in MVC - asp.net-mvc

Question

I have the following classes
public class Lookup
{
public int Id { get; set; }
public string Description { get; set; }
...
}
public class AccountTypeLookUp: Lookup
{
...
}
[Serializable]
public class Account
{
[HiddenInput]
public int AccountId { get; set; }
[Required, Display(Name="Account Name", Order=1)]
public string AccountName { get; set; }
[Display(Name="Account Description", Order=2)]
public string AccountDescription { get; set; }
[Required, Display(Name="Institution Name")]
public string InstitutionName { get; set; }
[Required, Display(Name="Account Number"), RegularExpression(#"[0-9]+",ErrorMessage="{0} can only be digits")]
public string AccountNumber { get; set; }
[Display(Name = "Routing Number"), RegularExpression(#"[0-9]+", ErrorMessage = "{0} can only be digits")]
public string RoutingNumber { get; set; }
[Required, Display(Name = "Account Type")]
public AccountTypeLookup AccountType { get; set; }
[ScaffoldColumn(false)]
public List<Transaction> TransactionCollection { get; set;}
public Account()
{
AccountId = default(int);
TransactionCollection = new List<Transaction>();
}
Now in my view I have a combobox which displays the description of Account Type with the values equal to the Id
<select class="input-validation-error" data-val="true" data-val-required="The Account Type field is required." id="AccountType" name="AccountType">
<option value="1">Savings</option>
<option selected="selected" value="2">Checking</option>
<option value="3">CreditCard</option>
</select>
Now how can I bind that comboBox to my local variable
account.AccountType.Id =?
My method signature is
[HttpPost]
public ActionResult Create(Account account)
Currently I get the error "The value '2' is invalid." which makes sense since it is looking for a complex type.

Answer 1

You have two options. The first option is to do it the way you're doing it now and that is NOT using an html helper:
<select class="input-validation-error" data-val="true" data-val-required="The Account Type field is required." id="AccountType" name="AccountType">
<option value="1">Savings</option>
<option selected="selected" value="2">Checking</option>
<option value="3">CreditCard</option>
</select>
But you have to change the id and the name to the following. But take note that the AccountType will not have the description with it. As you can only bind to a single property from the comboxbox and that would be to bind to the Id property.
id="AccountType_Id" name="AccountType.Id"
Your second option is to use DropDownListFor so you are guaranteed that binding works well. You have to build the selectlistitem though, either in the controller or in the view, best practice dictates that you build it in the controller and pass it to your view. So you can have something like:
#Html.DropDownListFor(m => m.AccountType.Id, Model.AccountTypes)
Model though is a viewmodel that can be mapped back to your Account class. If you do not want to use a viewmodel and use Account directly on your view then you need to create the list (Model.AccountTypes) in a ViewBag. Then you need to modify the DropDownListFor:
#Html.DropDownListFor(m => m.AccountType.Id,
(IEnumerable<SelectListItem>)ViewBag.AccountTypes)
// you might be pulling these values from a database,
// this is just an example of how you will build the list in the controller,
// you might build this in a for-loop, foreach or linq
ViewBag.AccountTypes = new List<SelectListItem> {
new SelectListItem { Value = "1", Text="Savings"},
new SelectListItem { Value = "2", Text="Checking"},
new SelectListItem { Value = "3", Text="CreditCard"},
};

Answer 2

I think MVC model binding knows to bind the query string Controller/Create?accountType.id=3 to account.AccountType.Id = 3
So try changing
<select class="input-validation-error" data-val="true" data-val-required="The Account Type field is required." id="AccountType" name="AccountType">
to
<select class="input-validation-error" data-val="true" data-val-required="The Account Type field is required." id="AccountType_Id" name="AccountType.Id">
See the recursive model binding section here: http://msdn.microsoft.com/en-us/magazine/hh781022.aspx