How to access a ListBox within a custom control with Javascript in the aspx page.

Rico MNC

Turns out my previous solution was a trip down an evil rabbit hole due to reusing a global variable from my JavaScript in my code behind (doh). Here is the corrected solution, which is a bit uglier: First, in the custom control I made a public property for the listbox ClientID within the control I wished to access in my Javascript:

public partial class Controls_Locations : System.Web.UI.UserControl
{
public ListBox Locations
{
get {return lbControlVehicles.ClientID; }

}

Then in my page code behind I provided a public property for this listbox ClientID string:

private Controls_Locations userLocations;

public string UserVehiclesListBox
{
get { return userLocations.Locations; }

}

In my Page_Load I initialize userLocations:

protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
userLocations = this._Locations1;// _Locations1 is the custom control in my aspx file which contains the listbox I want to access

In my aspx file using Javascript:

<uc1:RastracUserVehicle_Locations ID="RastracUserVehicle_Locations1" runat="server" />

var myLocationList;

function getLocationListBox()
{
myLocationList = $get("<%=UserVehiclesListBox%>");

//myLocationList is now the listbox contained within the custom control

}

I used a "global" Javascript variable so that I only need to get the list once. I have not yet discovered whether accessing the list will cause a post back to the server everytime.