Untitled

protected void Page_Load(object sender, EventArgs e)
{
    PopulateDropDown();
}
public void PopulateDropDown()
{
    SqlCommand cmd = new SqlCommand("SELECT * FROM [Product]", new SqlConnection(ConfigurationManager.AppSettings["ConnString"]));
    cmd.Connection.Open();

    SqlDataReader ddlValues;
    ddlValues = cmd.ExecuteReader();

    showOrders.DataSource = ddlValues;
    showOrders.DataValueField = "ProductName";
    showOrders.DataTextField = "ProductName";
    showOrders.DataBind();

    cmd.Connection.Close();
    cmd.Connection.Dispose();


}

<body>
    <form id="form1" runat="server">
    <div>
    <asp:DropDownList ID="showOrders" AutoPostBack="true" runat="server" OnSelectedIndexChanged="showOrders_SelectedIndexChanged"></asp:DropDownList>
    <asp:Label ID="showContainingOrders" runat="server"></asp:Label>
    </div>
    </form>
</body>