ASP.NET MVC Binding to a dictionary

Question

I'm trying to bind dictionary values within MVC.

Within the action I have:

model.Params = new Dictionary<string, string>();

model.Params.Add("Value1", "1");
model.Params.Add("Value2", "2");
model.Params.Add("Value3", "3");

and within the view I have:

@foreach (KeyValuePair<string, string> kvp in Model.Params)
{ 
<tr>
  <td>
    <input type="hidden" name="Params.Key" value="@kvp.Key" />
    @Html.TextBox("Params[" + kvp.Key + "]")
  </td>
</tr>
}

But the view doesn't display the initial values, and when the form is submitted the Params property is null?

Answer 1

In ASP.NET MVC 4, the default model binder will bind dictionaries using the typical dictionary indexer syntax property[key].

If you have a Dictionary<string, string> in your model, you can now bind back to it directly with the following markup:

<input type="hidden" name="MyDictionary[MyKey]" value="MyValue" />

For example, if you want to use a set of checkboxes to select a subset of a dictionary's elements and bind back to the same property, you can do the following:

@foreach(var kvp in Model.MyDictionary)
{
    <input type="checkbox" name="@("MyDictionary[" + kvp.Key + "]")"
        value="@kvp.Value" />
}