disable specific menu item on form load

[JJ]

I load radmenu from sitemap, now i like to disable one manu item - "ADMIN" on form load.
I tried the following code, but menuitem always returns null so it can never be disable.

RadMenuItem menuitem = mainMenu.FindItemByValue("ADMIN");  
if (menuitem != null)

 

{

menuitem.Enabled =

false;  

 

 

  

}
What i did wrong?
Thanks

 

 

 

 

 

 

 

[JJ]

 

private void DisableItemsFromText(string texttodisable)
{
    var items = mainMenu.GetAllItems();
    int total_items = items.Count;
    for (int i = 0; i < total_items; i++)
    {
        if (items[i].Text.ToUpper()== texttodisable)
        {
            items[i].Enabled = false;
            items[i].NavigateUrl = "";
        }
    }
}

The above code works for me