Jquery Select and Change selector and event .How to Post data using jquery to mvc and web api action methods

Jquery :Change event in Jquery Method:

Demo

    $("#drpCountry").change(function () {
            var id = $("#DrpCountry").val();
           alert(id);
        });
HTML

  <select id="drpCountry">

        <option value="">SELECT</option>

        <option value="USA">America</option>

        <option value="RSA">Russia</option>

        <option value="JPN">Japan</option>

    </select>

Jquery :selected Selector

In the below demo jQuery :selected selector to find the selected option value in the dropdown list.

  if ($('#drpCountry:selected').val() == "") {
        alert("Please select the Country Name);
    }

HTML

  <select id="drpCountry">

        <option value="">SELECT</option>

        <option value="USA">America</option>

        <option value="RSA">Russia</option>

        <option value="JPN">Japan</option>

    </select>

How to Post value to  mvc Action method using jquery .
or
How to Post values to Web API action method  using jquery .

Example

function DeleteUsers(userId) {

    $.ajax({
        type: 'POST',
        url: urlString + 'User/DeleteUser/',
        data: { UID: userId },
        success: function (data) {
         alert("Data SuccessFully Deleted");

        },
        error: function (xhr, ajaxOptions, thrownError) {
            //ON Error
            alert(xhr.status);

        }

    });
}