How to get the value of an Html.DropDownList to pass its value as a parameter to a partial view in MVC asp.net

I have the following dropdownlist, which shows the values ​​5,10 and 15:

<%     Dim listItems = New List(Of ListItem) From { _
        New ListItem() With { _
            .Text = "5", _
            .Value = 5 _
        }, _
        New ListItem() With { _
            .Text = "10", _
            .Value = 10 _
        }, _
        New ListItem() With { _
            .Text = "15", _
            .Value = 15 _
        } _
    }
%>
<%: Html.DropDownList("listado_noticia_length", New SelectList(listItems, "Value", "Text"), New With {Key .[class] = "form-control estilo_dropdownlist input-sm", Key .[onchange] = "javascript:registro_mostrar();"})%>

but I need to pass the selected value of the DropDownList (in this case its id would be list_news_length) to a parameter of this partial view, specifically to the row_count variable:

<%: Html.Action("partialListadoNoticia", "Noticias", New With {.pag = 1, .cant_filas = recibir el valor del dropdownlist listado_noticia_length ¿como?})%>

I don't know how I would send the value of the dropdownlist as a parameter to a variable of the partial view. Syntactically I don't know. I need to reference the value of dropdownlist, such as <%:Dim value_dropdownlist_selected= list_news_length.selectValue%>

That would be my question. Thanks in advance.