How To Get Text and Value Of DropdownList Using ButtonClick

In this article i will explain how to get selected value and text of dropdownlist 
<!DOCTYPE html>
 <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server">
            <asp:ListItem Text="Select Course" Value="-1"></asp:ListItem>