ASP.NET MVC - Custom model binder able to process arrays

Question

I need to implement a functionality to allow users to enter price in any form, i.e. to allow 10 USD, 10$, $10,... as input.

I would like to solve this by implementing a custom model binder for Price class.

 class Price { decimal Value; int ID; } 

The form contains an array or Prices as keys

keys:
"Prices[0].Value"
"Prices[0].ID"
"Prices[1].Value"
"Prices[1].ID"
...

The ViewModel contains a Prices property:

public List<Price> Prices { get; set; }

The default model binder works nicely as long as the user enters a decimal-convertible string into the Value input. I would like to allow inputs like "100 USD".

My ModelBinder for Price type so far:

public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
    Price res = new Price();
    var form = controllerContext.HttpContext.Request.Form;
    string valueInput = ["Prices[0].Value"]; //how to determine which index I am processing?
    res.Value = ParseInput(valueInput) 

    return res;
}

How do I implement a custom model Binder that handles the arrays correctly?

Answer 1

1) Create a dictionary 2) loop through the Request.Form keys 3) split the key by the [ char4 4) check if the key exists in the dictionary, if it does, use that Price object. if not add a new Price object to the dict. 5) use the default ModelBinder to bind each Price.

Answer 2

Got it: The point is to not try to bind a single Price instance, but rather implement a ModelBinder for List<Price> type:

    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        List<Price> res = new List<Price>();
        var form = controllerContext.HttpContext.Request.Form;
        int i = 0;
        while (!string.IsNullOrEmpty(form["Prices[" + i + "].PricingTypeID"]))
        {
            var p = new Price();
            p.Value = Process(form["Prices[" + i + "].Value"]);
            p.PricingTypeID = int.Parse(form["Prices[" + i + "].PricingTypeID"]);
            res.Add(p);
            i++;
        }

        return res;
    }

//register for List<Price>
ModelBinders.Binders[typeof(List<Price>)] = new PriceModelBinder();

Answer 3

Look into this also:

http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx