title: How to keep DropDownList1 selected value after postback?
body: <p>I have two DropDownLists. Once a DropDownList1 value is selected, DropDownList2 will populate based on Dropdownlist1.</p>
  
  <p>But after the page refreshes, the dropdownlist1 selected value is changed to the top-most value (the DropDownList is populate by a database).</p>
  
  <p>.aspx:</p>
  
  <pre><code>&lt;asp:DropDownList ID="DropDownList1" runat="server" Width="300px" CssClass="makeselect" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="True" AppendDataBoundItems="true"&gt;
  &lt;/asp:DropDownList&gt;
  </code></pre>
  
  <p>.cs:</p>
  
  <pre><code>protected void Page_Load(object sender, EventArgs e) {      
  
      DataTable subjects = new DataTable();
  
      if (Page.IsPostBack == false) {
          using (SqlConnection con = new SqlConnection(constring)) {
  
              SqlDataAdapter adapter = new SqlDataAdapter("SELECT VehicleMake FROM VehicleDB", con);
              adapter.Fill(subjects);
  
              con.Open();
  
              DropDownList1.DataSource = subjects;
              DropDownList1.DataTextField = "VehicleMake";
              DropDownList1.DataValueField = "";
              DropDownList1.DataBind();
  
              con.Close();
          }
      }
  }
  
  protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) {
      string makename = DropDownList1.SelectedItem.Value;
      keepname = makename;
  
      Response.Redirect("default.aspx?QSVehicleMake="+makename);
  }
  </code></pre>