Data Binding Exception With @Html.DropDownListFor

Question

I am having trouble binding values to a Drop Down List.

Model

public class DummyModel
{
    ...
    public int? OptionID { get; set; }
    ...
}

Line In View Causing Exception

@Html.DropDownListFor(model => model.OptionID, new SelectList(ViewBag.AvailableOptions, "ID", "Name"))

The Contents of the ViewBag

?ViewBag.AvailableOptions
Count = 4
    [0]: {[3, Average Speed]}
    [1]: {[4, Snails pace]}
    [2]: {[1, Super Fast]}
    [3]: {[2, Super Slow]}

The exception that gets generated:

System.Web.HttpException: 'DataBinding: 'System.Collections.Generic.KeyValuePair`2[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.String, mscorlib, Version=4.0.0.0, Culture=neutral,

Please add the action code so that we can see what you are assigning to ViewBag.AvailableOptions — Camilo Terevinto
– Camilo Terevinto, Commented Apr 30, 2018 at 15:55

Noémie Lord · Accepted Answer · 2018-04-30 16:29:26Z

1

If (as mentioned in the comments / from the text of the exception), ViewBag.AvailableOptions is a dictionary you'll want to change the Id and Value properties of your select list like so :

new SelectList(ViewBag.AvailableOptions, "Key", "Value")

Since a dictionary is basically a list of KeyValuePair objects when enumerated, its properties are (as one could imagine) Key and Value.

answered Apr 30, 2018 at 16:29

Noémie Lord

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1 Comment

user1289397 Over a year ago

Thank you Francis! This works the way I would expect.

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