ModelBinding with Steve Sandersons BeginCollectionItem

Question

I'm using Steve Sandersons BeginCollectionItem extension to help with binding lists of items. This works fine for primitive types. The problem I'm having is that for a custom model binder that I've written I can't see how to generate the full name and index of the item that I'm binding to.

Currently my model binder looks like this:

public class MoneyModelBinder : DefaultModelBinder 
{
    protected override void OnModelUpdated(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var valueResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".Amount");

        if (valueResult != null)
        {
            var value = valueResult.AttemptedValue;
            var currencyCode = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".Iso3LetterCode").AttemptedValue;

            var money = (Money) bindingContext.Model;

            Money parsedValue;
            if (String.IsNullOrEmpty(value))
            {
                money.Amount = null;
                return;
            }

            var currency = Currency.FromIso3LetterCode(currencyCode);

            if (!Money.TryParse(value, currency, out parsedValue))
            {
                bindingContext.ModelState.AddModelError("Amount", string.Format("Unable to parse {0} as money", value));
            }
            else
            {
                money.Amount = parsedValue.Amount;
                money.Currency = parsedValue.Currency;
            }
        }
        else
        {
            base.OnModelUpdated(controllerContext, bindingContext);
        }
    }
}

My ViewModel Lokks like this (some propertis omitted for clarity):

public class EditFeeEarningCapacityViewModel
{

    public List<FeeEarner> FeeEarners { get; set; }

    public class FeeEarner
    {
        public Money AverageChargeOutRate { get; set; }
    }
}

My Edit Template for the Money type looks like this:

@model Core.Money
@{
    int decimalPlaces;
    if(!int.TryParse(string.Format("{0}", ViewData["DecimalPlaces"]), out decimalPlaces))
    {
        decimalPlaces = 0;
    }
}
<div class="input-prepend">
    <span class="add-on">@Model.Currency.Symbol</span>@Html.TextBoxFor(m => m.Amount,
                                                                new
                                                                {
                                                                    placeholder = string.Format("{0}", Model.Currency),
                                                                    @class = "input-mini",
                                                                    Value = String.Format("{0:n" + decimalPlaces + "}", Model.Amount)
                                                                })
</div>
@Html.HiddenFor(x => x.Iso3LetterCode)

For a form that has post values like this:

FeeEarners.index    3fa91d09-0617-4bea-ae3f-d84862be8c04

FeeEarners[3fa91d09-0617-4bea-ae3f-d84862be8c04].feeEarner.AverageChargeOutRate.Amount  500
FeeEarners[3fa91d09-0617-4bea-ae3f-d84862be8c04].feeEarner.AverageChargeOutRate.Iso3LetterCode  GBP

I can't see how to detect the index of the item or the property name that I'm binding to. So essentially, how do I find the index of the item I'm trying to bind to and the name of the property that I'm trying to bind the data from?

Answer 1

I am not fimilar with that Helper but for collection i am doing a bit different trick.

define key

var key = "EditModel[{0}].{1}";

var index = 0;

then build form

foreach(var fee in Model.FeeEarners){
   @Html.TextBox(string.Format(key, index, "PropertyNameFromYourFeeClass"));
//It will build text box and set value
}

On Controller side create action with input parameter

public ActionResult Save(EditFeeEarningCapacityViewModel editModel){
...your code here
}