public partial class _Default : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        if (!IsPostBack)

        {

            bind();

            //pictureview();

        }

    }

    protected void bind()

    {

        SqlConnection conn = new SqlConnection("data source=(local);database=monkey;uid=monkey;pwd=donkey;");

        conn.Open();

        SqlCommand cmd = new SqlCommand("select pic from picsave", conn);

        SqlDataAdapter database = new SqlDataAdapter(cmd);

        DataSet ds = new DataSet();

        database.Fill(ds);

        DropDownList1.DataSource = ds;

  //DropDownList1.DataTextField = "pic";

        DropDownList1.DataValueField = "pic";

        DropDownList1.DataBind();

    }

    protected void pictureview()

    {

  Image1.ImageUrl = Server.MapPath("img/")+ DropDownList1.SelectedValue.ToString().Trim();

    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

    {

        pictureview();

    }

}