ASP.NET

<asp:DropDownList ID="DropDownList1" runat="server" Visible="false" AutoPostBack="True" onSelectedIndexChanged="nextStep"  ></asp:DropDownList>

<asp:DropDownList ID="DropDownList2" runat="server" Visible="false" AutoPostBack="True" onSelectedIndexChanged="nextStep"  ></asp:DropDownList>

TMFoust wrote:

Nope, that's not it. If I set AutoPostBack, the dropdownlist does not retain the selected change.

if(!Page.ISPostBack)     // This will load the data if the page is not a post back request.
   {
    //Bind Data in Dropdown list
   }

TMFoust wrote:

Christian Graus answererd a similar question (Re: Problem in handling SelectedIndexChanged event of a dynamically created drop down) and stated that the dropdownlist needed to be created before page load.

public partial class _Default : System.Web.UI.Page
{
    public string study = "";
    public string rowfile = "";
    public string colfile = "";
    public string path = "";
    public string weight = "";
    public TabEngineClass tab;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (this.Page.IsPostBack == false)
        {
          DataSet StudyList = new DataSet();
          StudyList.ReadXml("C:\\WorkingFiles\\TestChartGrid\\TestChartGrid\\StudiesList.xml");
          DropDownList3.DataSource = StudyList;
          DropDownList3.DataValueField = "path";
          DropDownList3.DataTextField = "cycle";
          DropDownList3.DataBind();
        }
    }

    protected void displayDefinitions(object sender, EventArgs e)
    {
        study = DropDownList3.SelectedItem.Text;
        path = DropDownList3.SelectedItem.Value;
        Label1.Visible = true;
        Label2.Visible = true;
        DropDownList1.Visible = true;
        DropDownList2.Visible = true;

        DataSet RowList = new DataSet();
        RowList.ReadXml(path + ".xml");
        DropDownList1.DataSource = RowList;
        DropDownList1.DataValueField = "path";
        DropDownList1.DataTextField = "file";
        DropDownList1.DataBind();
        DataSet ColumnList = new DataSet();
        ColumnList.ReadXml(path + ".xml");
        DropDownList2.DataSource = ColumnList;
        DropDownList2.DataValueField = "path";
        DropDownList2.DataTextField = "file";
        DropDownList2.DataBind();
    }

protected void nextStep(object sender, EventArgs e)
{
    if (rowfile != "")
    {
        if (colfile != "")
        {
            RadioButtonList1.Visible = true;
        }
        else
        {
            colfile = DropDownList2.SelectedItem.Value + DropDownList2.SelectedItem.Text;
        }
    }
    else
    {
        rowfile = DropDownList1.SelectedItem.Value + DropDownList1.SelectedItem.Text;
    }
}