Question

Why is my dropdownlist not binding? Using the DropDownListFor Razor helper function.

View:

@Html.DropDownListFor(m => m.ModelObject.VatRate, Model.VatRatesList)

ViewModel:

    public SelectList VatRatesList
    {
        get
        {
            return new SelectList(
                new Dictionary<decimal, string>
                {
                    { 0m, string.Empty },
                    { 1.2m, "20%" },
                    { 1m, "0%" }
                }, "Key", "Value",
                ModelObject.VatRate ?? 0m);
        }
    }

Thanks.

Answer 1

UPDATE

On further investigation I have found out that this is something to do with the model property that I am trying to bind. It is a nullable decimal. When I change it to a decimal, the correct value is selected from the list.

Here is where things start to get weird. If I use 4 decimal places for the dictionary keys, it works with a nullable decimal model property. In other words, this works:

 public SelectList VatRatesList
    {
        get
        {
            return new SelectList(
                new Dictionary<decimal, string>
                {
                    { 0.0000m, string.Empty },
                    { 1.2000m, "20%"},
                    { 1.0000m, "0%"}
                }, "Key", "Value");
        }
    }

I have no idea why. Perhaps html helper uses ToString() internally. I think ToString() would give a 4dp string representation of the decimal. I’ll have to look at the MVC source code to find out.