DropDownList SelectedIndexChanged AutoPostBack C# ASP.NET

    protected void Page_Load(object sender, EventArgs e) {
      // Request inputs
      // Request SessionID
      // Request if got questions already
 
      if(!IsPostBack) {
        LoadStates("");
        chkDeed.Attributes.Add("onclick", "javascript:checkDeed()");
        chkMortgage.Attributes.Add("onclick", "javascript:checkMortgage()");
        chkRefi.Attributes.Add("onclick", "javascript:checkMortgageRefi()");
        chkAssignment.Attributes.Add("onclick", "javascript:checkAssignment()");
        chkRelease.Attributes.Add("onclick", "javascript:checkRelease()");
        chkNewPolicy.Attributes.Add("onclick", "javascript:checkTitle()");
        chkReissuePolicy.Attributes.Add("onclick", "javascript:checkTitleReissue()");
 
        // Set Sessions
        Session["State"] = null;
        Session["County"] = null;
        Session["City"] = null;
 
        DisplayControl.Display = 0;
        DisplayControl.SetPanels(ref pnlOffice, ref pnlDocTypes, ref pnlQuestions, ref pnlDetails, 1);
 
        ClearQuestions();
 
      } else { // Page Posted Back
      }
    }
 
    private void LoadStates(string pState) {
      DataSet ds = new DataSet();
      FileStream fs = new FileStream(Server.MapPath("State.xml"), FileMode.Open, FileAccess.Read);
      StreamReader sr = new StreamReader(fs);
      ds.ReadXml(sr);
      fs.Close();
      DataView dv = new DataView(ds.Tables[0]);
      ddStates.DataSource = dv;
      ddStates.DataMember = "state";
      ddStates.DataTextField = "display";
      ddStates.DataValueField = "value";
      ddStates.DataBind();
      ddStates.SelectedValue = pState;
    }
 
    protected void ClearQuestions() {
      Session["Q_WasAsked"] = null;
    }
 
    protected void ddStates_SelectedIndexChanged(object sender, EventArgs e) {
      string ErrorMessage = "";
 
      if(ddStates.SelectedIndex != 0) {
        imgStateSummary.Visible = true;
      } else {
        imgStateSummary.Visible = false;
        imgOfficeDetail.Visible = false;
      }
 
      string state = ddStates.SelectedItem.Value;
      Session["State"] = state;
 
      // This doesn't work
      DataSet ds = new DataSet();
      ds = Helper.GetCounties(state, "%%", ref ErrorMessage);
 
      ddCounties.Items.Clear();
      ddCounties.Items.Add(new ListItem("Choose a County", ""));
 
      foreach(DataRow dr in ds.Tables[0].Rows) {
        ddCounties.Items.Add(new ListItem(dr["Name"].ToString(), state));
      }
 
      // This works
      //DataSet ds = new DataSet("Jurisdiction");
      //FileStream fs = new FileStream(Server.MapPath("Jurisdiction.xml"), FileMode.Open, FileAccess.Read);
      //StreamReader sr = new StreamReader(fs);
      //ds.ReadXml(sr);
      //fs.Close();
      //DataView dv = new DataView(ds.Tables[0]);
 
      //dv.Table = ds.Tables[0];
      //dv.RowFilter = "State = '" + state + "'";
      //ddCounties.DataSource = dv;
      //ddCounties.DataMember = "jurisdiction";
      //ddCounties.DataTextField = "county";
      //ddCounties.DataValueField = "county";
      //ddCounties.DataBind();
 
      //***************
 
      if(ddCounties.SelectedItem == null) {
        imgOfficeDetail.Visible = false;
      } else {
        if(ddCounties.SelectedItem.Value != "Choose a County") {
          imgOfficeDetail.Visible = true;
        } else {
          imgOfficeDetail.Visible = false;
        }
      }
 
      //***************
      // Reset inputs when user selects a state
      //  Clean slate.
      ClearQuestions();
      litQuestions.Text = "";
      litError.Text = "";
      litInfo.Text = "";
    }
 
    protected void ddCounties_SelectedIndexChanged(object sender, EventArgs e) {
      if(ddCounties.SelectedIndex != 0) {
        imgOfficeDetail.Visible = true;
      } else {
        imgOfficeDetail.Visible = false;
      }
 
      // Reset inputs when user selects a county
      //  Clean slate.
      string county = ddCounties.SelectedItem.Text;
      Session["County"] = county;
 
      ClearQuestions();
      litQuestions.Text = "";
      litError.Text = "";
      litInfo.Text = "";
    }