.NET: DropDownList not showing up

.NET: DropDownList not showing up

When I run this, the dropdownlist doesn't show up at all. It was showing
up at an earlier point; I'm not sure what I changed to make it not work.
Only the submit button shows up.
Enter Wellness Activity
Select Activity Type:<br />
@{
List<Activity> acts = ViewBag.Activities;
var selectItems = new SelectList(acts, "code", "shortTitle");
ViewBag.selectItems = selectItems;
}
<div class="input">
@{
Html.BeginForm("ActivitySelected", "Home");
Html.DropDownList("selectItems");
<br />
<button name="submit" value="Submit">Submit</button>
// Html.EndForm();
}
</div>
</div>