Use this code instead to fetch all the selected values in a particular listbox, say listbox1 :
List<string> Stringlist = new List<string>();
for (int i = 0; i < ListBox1.Items.Count; i++)
{
if (ListBox1.Items[i].Selected == true)
{
Stringlist.Add(ListBox1.Items[i].ToString());
}
}</string></string>
Listbox.selecteditem is not string so the conversion error was there...
Use the above code and I think you will get the desired result..
Thanks