Need to build a datagrid with the value of selected index from dropdownlist.

I need to build a datagrid with using the information that was used in from a dropdownlist.
I start of with a dropdownlist of code types. The user selects a code type and presses the button
and we want to use the index of the dropdownlist (CODE_TYPE_ID) to build the datagrid.

The select will be getting codes for a specific code type. SELECT CODE_DESC WHERE CODE_TYPE_ID = SELECTEDINDEX

This will be need to build the datagrid. Except I have problems getting started.
Here is the code: How should I go to modify the code?

public class codestypes : System.Web.UI.Page
      {
            protected System.Web.UI.WebControls.Label lblFullName;
            protected System.Web.UI.WebControls.TextBox newCountry;
            protected System.Web.UI.WebControls.TextBox newName;
            protected System.Web.UI.WebControls.DataGrid DataGrid1;
            protected System.Web.UI.WebControls.Label pathTitle;
            protected System.Web.UI.WebControls.Label typeName;
            protected System.Web.UI.WebControls.DropDownList DropDownList1;
            protected System.Web.UI.WebControls.Button Button1;
            protected System.Web.UI.WebControls.Button addCountry;
      
            private void Page_Load(object sender, System.EventArgs e)
            {
                  lblFullName.Text = PDM.varSession.getFullName();
                  
                  if (!Page.IsPostBack)
                  {
                        string strConn = ConfigurationSettings.AppSettings["CONNECTION_STRING_PDM"];                              
                        SqlConnection conDB = new SqlConnection(strConn);
                        SqlCommand myCMD;
                        myCMD = new SqlCommand("Select * From PDM_CODE_TYPES", conDB);
                        SqlDataAdapter adapter = new SqlDataAdapter(myCMD);
                        DataSet dataset = new DataSet();  
                        adapter.Fill(dataset,"PDM_CODE_TYPES");
                        // apply sort to the DefaultView to sort by CompanyName
                        dataset.Tables[0].DefaultView.Sort = "CODE_TYPE_NAME";
                        DropDownList1.DataSource = dataset.Tables["PDM_CODE_TYPES"].DefaultView;
                        DropDownList1.DataTextField = "CODE_TYPE_NAME"; // what to display
                        DropDownList1.DataValueField = "CODE_TYPE_ID"; // what to set as value
                        DropDownList1.DataBind();
                        BindData();
                  }
            }

            void BindData()
            {
                  string strConn = ConfigurationSettings.AppSettings["CONNECTION_STRING_PDM"];
                  SqlConnection conn = new SqlConnection(strConn);
                  SqlDataAdapter Cmd = new SqlDataAdapter(sql, conn);

                  DataSet DS = new DataSet();
                  conn.Open();
                  Cmd.Fill(DS);
                  DataGrid1.DataSource = DS;
                  DataGrid1.DataBind();
                  conn.Close();
            }


            #region Web Form Designer generated code
            override protected void OnInit(EventArgs e)
            {
                  //
                  // CODEGEN: This call is required by the ASP.NET Web Form Designer.
                  //
                  InitializeComponent();
                  base.OnInit(e);
            }
            
            /// <summary>
            /// Required method for Designer support - do not modify
            /// the contents of this method with the code editor.
            /// </summary>
            private void InitializeComponent()
            {    
                  this.DataGrid1.CancelCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_CancelCommand);
                  this.DataGrid1.EditCommand += new System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_EditCommand);
                  this.DataGrid1.ItemDataBound += new System.Web.UI.WebControls.DataGridItemEventHandler(this.DataGrid1_ItemDataBound);
                  this.DropDownList1.SelectedIndexChanged += new System.EventHandler(this.DropDownList1_SelectedIndexChanged);
                  this.Button1.Click += new System.EventHandler(this.Button1_Click);
                  this.Load += new System.EventHandler(this.Page_Load);

            }
            #endregion

            private void DataGrid1_EditCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
            {
                  DataGrid1.EditItemIndex=e.Item.ItemIndex;
                  BindData();
            }

            private void DataGrid1_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
            {
                  if ((e.Item.ItemType == ListItemType.Item) || (e.Item.ItemType == ListItemType.AlternatingItem))
                  {
                        ((Button)e.Item.FindControl("edit")).Visible = true;
                        ((Button)e.Item.FindControl("update")).Visible = false;
                        ((Button)e.Item.FindControl("delete")).Visible = false;
                        ((Button)e.Item.FindControl("cancel")).Visible = false;

                        string bgColor;
                        if (e.Item.ItemType == ListItemType.Item)
                              bgColor = "#EFF5DA";
                        else
                              bgColor = "#F0FFBB";

                        Label currencyName = (Label)e.Item.FindControl("currencyName");
                        Label isoCode = (Label)e.Item.FindControl("iso");
                        
                        currencyName.Text = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "NAME"));
                        isoCode.Text = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "CODE"));

                        e.Item.Attributes.Add("onmouseover", "this.style.backgroundColor='#add8e6'");
                        e.Item.Attributes.Add("onmouseout", "this.style.backgroundColor='" + bgColor + "'");

                  }
                  if (e.Item.ItemType == ListItemType.EditItem)
                  {
                        ((Button)e.Item.FindControl("edit")).Visible = false;
                        ((Button)e.Item.FindControl("update")).Visible = true;
                        ((Button)e.Item.FindControl("delete")).Visible = true;
                        ((Button)e.Item.FindControl("cancel")).Visible = true;

                        TextBox txtName = (TextBox)e.Item.FindControl("txtName");
                        TextBox txtISO = (TextBox)e.Item.FindControl("txtISO");
                        HtmlInputHidden dbCurrencyName = (HtmlInputHidden)e.Item.FindControl("dbCurrencyName");
                        Label currencyID = (Label)e.Item.FindControl("currencyID");

                        txtName.Text = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "NAME"));
                        txtISO.Text            = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "code"));
                        dbCurrencyName.Value = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "NAME"));
                        currencyID.Text = Convert.ToString(DataBinder.Eval(e.Item.DataItem, "ID"));
                  }


            }

            private void DataGrid1_CancelCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
            {
                  DataGrid1.EditItemIndex=-1;
                  BindData();

            }

            private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
            {
            
            }

            private void Button1_Click(object sender, System.EventArgs e)
            {
            
            }
      }

Any help would be appreciated.