Question

How do I perform some logic when the user selects an item with a @Html.DropDownListFor?

Based on what the user clicks on, I want to update the Model and re-pass it with newly edited data.

The Drop Down List code is as follows:

@Html.DropDownListFor(m => m.Categories, Model.Categories, "Select a Category")

Answer 1

Simplest way is use jquery, for example:

$(document).ready(function() {
    $("#Categories").change(function() {
        var strSelected = "";
        $("#Categories option:selected").each(function() {
            strSelected += $(this)[0].value;
        });
        var url = "/Home/MyAction/" + strSelected; // or send with json

        $.post(url, function(data) {
            // do something if necessary
        });
    });
});