is passing the value.But how to pass other select box selected value in first select box function? When this happens, the onselect event fires, which will trigger an alert function. That's why I was thinking that get rid of autopostback from Listbox & do a JS script onchange event, then pass value from listbox to gridview. The onchange attribute fires the moment when the value of the element is changed. Tip: This event is similar to the oninput event. I want to show one combobox-A, which is an HTML