Ajax.ActionLink parameter from DropDownList - asp.net-mvc-4

Question

I have the following view part:
<div class="editor-label">
#Html.LabelFor(model => model.Type)
</div>
<div class="editor-field">
#Html.DropDownListFor(model => model.Type, ElangWeb.Helpers.ModelHelpers.GetExerciseTypes())
</div>
I want to have a link which will generate some partialview based on my model's Type property which is an Enum (I return different partial views based on the type),
I've added the following link:
#Ajax.ActionLink("AddExerciseItem",
"AddExerciseItem",
"Exercise",
new { type=#Model.Type},
new AjaxOptions() { HttpMethod="GET", InsertionMode = InsertionMode.InsertBefore, UpdateTargetId="ExerciseItems"})
My controller action is defined as follows:
public ActionResult AddExerciseItem(ExerciseType type)
{
return PartialView("ExerciseItemOption", new ExerciseItemOption());
}
I however does not work because I have the exeption "Object reference not set to an instance of an object" for my Model. How to resolve this issue?

Answer 1

You could use a normal link:
#Html.ActionLink(
"AddExerciseItem",
"AddExerciseItem",
"Exercise",
null,
new { id = "add" }
)
that you could unobtrusively AJAXify:
// When the DOM is ready
$(function() {
// Subscribe to the click event of the anchor
$('#add').click(function() {
// When the anchor is clicked get the currently
// selected type from the dropdown list.
var type = $('#Type').val();
// and send an AJAX request to the controller action that
// this link is pointing to:
$.ajax({
url: this.href,
type: 'GET',
// and include the type as query string parameter
data: { type: type },
// and make sure that you disable the cache because some
// browsers might cache GET requests
cache: false,
success: function(result) {
// When the AJAX request succeeds prepend the resulting
// markup to the DOM the same way you were doing in your
// AJAX.ActionLink
$('#ExerciseItems').prepend(result);
}
});
return false;
});
});
Now your AddExerciseItem controller action could take the type parameter:
public ActionResult AddExerciseItem(string type)
{
...
}