Question

I have an event handler in my view which reacts on clicking an id. On clicking on the id, I call a method1 in my controller.

In the same view I have a dropdownlost which I fill with ViewData which is set in my method1.

But, since in the beginning, Index is called, and the ViewData is still empty, I get error that there is no such ViewData to fill my dropdown list.

How to set the dropdown list only if the Viewdata isn’t eppty?

Answer 1

You could test if you have values in ViewData before outputting the dropdown list:

<% if (ViewData["values"] != null) { %>
    <%= Html.DropDownList("selectedValue", (IEnumerable<SelectListItem>)ViewData["values"]) %>
<% } %>

or even better if you are using view models:

<% if (Model.Values != null) { %>
    <%= Html.DropDownListFor(x => x.SelectedValue, Model.Values) %>
<% } %>