Model value not accessable - asp.net-mvc

Question

I have a model which holds some details about an account (Name, Id etc) and then it has a type called Transaction, which holds information about the currently selected account transaction. A transaction can then have many transaction lines. So I have a List<TransactionsLine> property.
I am trying to set the value of a Drop down list, using the model, the value being in the List<> property. At the moment, there can, and must, only be one item in the list.
#Html.DropDownListFor(x=>x.Transaction.TransactionLines[0].CategoryId, Model.TransactionReferences.Categories, new {#onchange="populateSubCategory()"})
However, when I run this, the list defaults to the first item in the list.
In debug mode, when I hover the mouse over x.Transaction.TransactionLines[0].CategoryId, it doesn't show me a value. But when hover over the collection, Model.TransactionReferences.Categories, I see it has a valid list. It just won't set the selected value.
Am I doing this wrong?
It works in other drop downs I use, BUT the select value is in the top most level of my model:
#Html.DropDownListFor(x => x.Transaction.ThirdPartyId, Model.TransactionReferences.ThirdParties, new { #class = "cmbThirdParty form-control", #onchange = "populateDefaults()" })
That one works fine.
Note, doing it manually, works:
<select class="form-control" id="cmbCategory" onchange="populateSubCategory()">
<option value="0">Select a One</option>
#foreach (var cat in Model.TransactionReferences.Categories)
{
//var selected = cat.Value == Model.Transaction.TransactionLines[0].CategoryId.ToString() ? "selected" : "";
<option value="#cat.Value">#cat.Text</option>
}
</select>
But doesn't feel like the best way to do it.
Model:
The main model passed to the view:
public class TransactionModel
{
public int BankAccountId { get; set; }
public string BankAccountName { get; set; }
public TransactionContainer Transaction { get; set; }
public TransactionReferenceModel TransactionReferences { get; set; }
public DateTime DefaultDate { get; set; }
}
The TransactionReferenceModel holds all my 'reference' data used to populate drop down lists:
public class TransactionReferenceModel
{
public List<SelectListItem> TransactionTypes { get; set; }
public List<SelectListItem> EntryTypes { get; set; }
public List<SelectListItem> SubCategories { get; set; }
public List<SelectListItem> Categories { get; set; }
public List<SelectListItem> ThirdParties { get; set; }
public List<SelectListItem> CostCentres { get; set; }
}
The TransactionContainer model holds allthe main details about the selected transaction:
public class TransactionContainer
{
public int Id { get; set; }
public int AccountId { get; set; }
public int TransactionTypeId { get; set; }
public string TransactionType { get; set; }
public int EntryTypeId { get; set; }
public string EntryType { get; set; }
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:dd/dd/yyyy}")]
public DateTime TransactionDate { get; set; }
public string ThirdParty { get; set; }
public int ThirdPartyId { get; set; }
public string Account { get; set; }
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "C2")]
public decimal Amount { get; set; }
public string Notes { get; set; }
public string CategoryDisplay { get; set; }
public string CostCentreDisplay { get; set; }
public decimal RunningBalance { get; set; }
public List<TransactionLine> TransactionLines { get; set; }
}
That then holds a list of transaction lines that make up the transaction. The transaction line holds the property I am trying to set the drop down to, which is CategoryId:
public class TransactionLine
{
public int Id { get; set; }
public int TransactionId { get; set; }
public int? CostCentreId { get; set; }
public string CostCentre { get; set; }
public int SubCategoryId { get; set; }
public string SubCategory { get; set; }
public int CategoryId { get; set; }
public string Category { get; set; }
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "C2")]
public decimal Amount { get; set; }
public string Notes { get; set; }
}
And here is how I am populating my model and sending it to the view:
public ActionResult EditTransaction(int? transactionId, int? bankAccountId)
{
// Create the main view object
var model = new TransactionModel
{
Transaction = new TransactionContainer
{
TransactionLines = new List<TransactionLine>()
}
};
if (transactionId != null) // This is an Edit, as opposed to an Add
{
var item = new TransactionService(currentUserId).GetTransaction(transactionId.Value);
// Populate the Reference object used to populate drop downs.
model.TransactionReferences = PopulateReferenceDate(model.TransactionReferences, item.TransactionLines[0].SubCategoryId);
model.BankAccountId = item.AccountId;
model.BankAccountName = item.Account.FullName;
model.DefaultDate = Session["DefaultDate"] != null
? DateTime.Parse(Session["DefaultDate"].ToString())
: DateTime.UtcNow;
model.Transaction.AccountId = item.AccountId;
model.Transaction.Amount = item.Amount;
model.Transaction.TransactionLines.Add(new TransactionLine
{
Id = item.TransactionLines[0].Id,
CategoryId = item.TransactionLines[0].SubCategory.CategoryId,
CostCentreId = item.TransactionLines[0].CostCentreId,
Notes = item.TransactionLines[0].Notes,
Amount = item.TransactionLines[0].Amount,
SubCategoryId = item.TransactionLines[0].SubCategoryId,
TransactionId = model.Transaction.Id
});
model.Transaction.EntryTypeId = item.EntryTypeId;
model.Transaction.Id = transactionId.Value;
model.Transaction.Notes = item.Notes;
model.Transaction.ThirdPartyId = item.ThirdPartyId;
model.Transaction.TransactionDate = item.TransactionDate;
model.Transaction.TransactionTypeId = item.TransactionTypeId;
}
else
{
// Populate the bank account details
var bank = new BankAccountService(currentUserId).GetBankAccountById(bankAccountId.Value);
model.TransactionReferences = PopulateReferenceDate(model.TransactionReferences, null);
model.BankAccountId = bank.Id;
model.BankAccountName = bank.FullName;
model.Transaction.TransactionLines.Add(new TransactionLine
{
TransactionId = model.Transaction.Id // Link the transaction line to the transaction.
});
var transactionDate = Session["DefaultDate"] != null
? DateTime.Parse(Session["DefaultDate"].ToString())
: DateTime.UtcNow;
// Populate the object to hold the Transaction data, so that we can use it and return it in the view.
model.Transaction.TransactionDate = transactionDate;
}
return View(model);
}

Answer 1

I think you should use the SelectList Constructor in your view, in order to indicate the default value, like this:
#Html.DropDownListFor(
x => x.Transaction.TransactionsLines[0].CategoryId,
new SelectList(Model.TransactionReferences.Categories, "Value", "Text", Model.Transaction.TransactionsLines[0].CategoryId)
)
You are not restricted to use List< SelectListItem > for the collections. You can use a List of a specific class also.
This is the Controller Action Method code:
public class HomeController : Controller
{
public ActionResult Index()
{
var m = new AccountModel();
m.Transaction = new Transaction();
m.Transaction.TransactionsLines = new List<TransactionsLine>();
m.Transaction.TransactionsLines.Add(new TransactionsLine() { CategoryId = 2 });
m.TransactionReferences = new TransactionReferences();
m.TransactionReferences.Categories = new List<SelectListItem>()
{ new SelectListItem() { Text = "Cat1", Value = "1" },
new SelectListItem() { Text = "Cat2", Value = "2" },
new SelectListItem() { Text = "Cat3", Value = "3" }
};
return View(m);
}
}