Populating items from dropdownlistbox to listbox

You can do something like this.

for this write following code:

 protected void Button1_Click(object sender, EventArgs e)
        {
            foreach (ListItem li in DropDownList1.Items)
            {
                ListBox1.Items.Add(li.Text);
            }
        }

it is button click event:Button1_Click
DropDownList1 id dropdownlist id
ListBox1 listbox id