问DropDownList没有在EditItemTemplate of RadGrid中显示选定的值

EN

<telerik:GridTemplateColumn UniqueName="AccountCode" HeaderText="Account Code">
       <ItemTemplate>
           <asp:Label ID="lblAcCode" runat="server" Text='<%# Eval("AccountCode")%>'></asp:Label>
       </ItemTemplate>
       <EditItemTemplate>
           <asp:Label ID="lblAcCode2" runat="server" Text='<%# Eval("AccountCode") + " - " + Eval("AccountDescription")%>'></asp:Label>
           <asp:DropDownList ID="ddlAcCode" DataTextField="AccountDescription" DataValueField="AccountCodeID" runat="server"/> 
       </EditItemTemplate>
</telerik:GridTemplateColumn>

    public DataTable GetAccCode(string CompanyCode)
        {
            SqlConnection con = new SqlConnection(strcon);
            SqlCommand cmd = new SqlCommand("[Invoice].[usp_tbl_AccountCode_DL_Test]", con);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@CompanyCode", CompanyCode);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            try
            {
                con.Open();
                da.Fill(dt);
                con.Close();
            }
            catch (Exception ex)
            {
            }
            return dt;
        }

    protected void RGGSTAcCode_ItemDataBound(object sender, GridItemEventArgs e)
        {

           if (e.Item is GridEditableItem && e.Item.IsInEditMode)
                {
                    //bind dropdwon while "Add" 
                    string CompanyCode = ddlCompany.SelectedValue.ToString();
                    GridEditableItem item = (GridEditableItem)e.Item;
                    DropDownList ddl = (DropDownList)item.FindControl("ddlAcCode");
                    ddl.DataSource = GetAccCode(CompanyCode);
                    ddl.DataTextField = "AccountDescription";
                    ddl.DataValueField = "AccountCodeID";
                    ddl.DataBind();
                    ddl.Items.Insert(0, "- Select -");

                    //Select particular dropdown value while "Edit"
                    string accCodeID =  item.GetDataKeyValue("AccountCodeID").ToString();
                    Label lblAcCode2 = item.FindControl("lblAcCode") as Label;

                    //if (!string.IsNullOrEmpty(lblAcCode2.Text))
                    //{
                        ddl.SelectedValue = lblAcCode2.Text;
                    //}
                    //string SelectedVal =  ddl.SelectedValue;

                if (!string.IsNullOrEmpty(lblAcCode2.Text))
                {
                    SqlConnection con = new SqlConnection(strcon);
                    con.Open();
                    SqlDataAdapter adapter = new SqlDataAdapter();
                    adapter.SelectCommand = new SqlCommand("SELECT [AccountCode]+' - '+[AccountDescription] as [AccountDescription] FROM [Sunway_AP].[Invoice].[tbl_AccountCodeTest] where AccountCodeID='" + accCodeID + "' ", con);

                    DataTable dt = new DataTable();
                    try
                    {
                        adapter.Fill(dt);
                    }
                    finally
                    {
                        con.Close();
                    }
                    ddl.SelectedValue = dt.ToString();
                    string SelectedVal = ddl.SelectedValue;
                }

             }
         }

ALTER PROCEDURE [Invoice].[usp_tbl_AccountCode_DL_Test]
    @CompanyCode nvarchar(50)
AS
BEGIN   
    SET NOCOUNT ON;   
       SELECT [AccountCodeID] ,[AccountCode]+' - '+[AccountDescription] as [AccountDescription]     
       FROM [Sunway_AP].[General].[tbl_AccountCode] (NOLOCK)
       Where [CompanyCode] = @CompanyCode
       order by [AccountCode]+' - '+[AccountDescription]

END