protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)

    {

        DropDownList4.Items.Add(new ListItem("--Select Project Name--", ""));

        DropDownList4.AppendDataBoundItems = true;

        String strConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;

        String strQuery = "Select * from " + DropDownList3.SelectedItem + " ";

        SqlConnection con = new SqlConnection(strConnString);

        SqlCommand cmd = new SqlCommand();

        cmd.CommandType = CommandType.Text;

        cmd.CommandText = strQuery;

        cmd.Connection = con;

        try

        {

            con.Open();

            DropDownList4.DataSource = cmd.ExecuteReader();

            DropDownList4.DataTextField = "ProjectName";

            DropDownList4.DataValueField = "project_name";

            DropDownList4.DataBind();

            if (DropDownList4.Items.Count > 1)

            {

                DropDownList4.Enabled = true;

            }

            else

            {

                DropDownList4.Enabled = false;

            }

        }

        catch (Exception ex)

        {

             throw ex;

        }

        finally

        {

            con.Close();

            con.Dispose();

        }

I am using this code to populate drodownlist4 on the basis of dropdownlist3 selection. but it is not working

i am not getting any error as well as not getting any value in dropdownlist 4

now plz help me.....