Struggling to retrieve user choice from a dropdown using SAFE

I am using SAFE for the first time, and I am struggling to find a way to update the model / state when a select / dropdown is clicked on by the user.

This is the code from the View section:

let view (model: PageModel) dispatch =
... [
           prop.children [
                  for (value, text) in plainData do
                          Html.option [
                                               prop.value value
                                               prop.text text
                                               prop.onClick (fun _ -> dispatch (PlainDataChanged value))
                                               ] ] ]

The code above has no errors but the onClick event, which I hoped would send ‘value’ to Update Msg below, does not seem to send anything:

let update (msg: Msg) (model: PageModel) : PageModel * Cmd<Msg> =
    match msg with
    | PlainDataChanged indx ->   { model with
                                                       serverState = Idle
                                                       dataModel = {model.dataModel with PlainIndex = indx }
                                                    }, Cmd.none

Equivalent code has worked fine for processing user input via radio buttons and from a textarea, and I am at a loss trying to work out how to send the ‘value’ when the dropdown / select element is changed. Any help gratefully received!

The answer turned out to be so easy that I am embarrassed that it has taken me several days to find it. The parameter to the onClick function needed to be converted to an integer:

prop.onClick (fun ev  -> dispatch (PlainDataChanged (int ev)))