Cascading dropdowns and control state (no AJAX, Jquery or Updated Panels) - cascadingdropdown

Question

I am having a weird post back problem. I have two dropdowns, project and charge codes. Projects selection populates the charge code drop down. I noticed that when I select a charge code, the value appears in the dropdown for a split second and then changes to the first choice in the dropdown. The Index change of that dropdown triggers and the value is the first option in the dropdown, not the one selected. I am not sure why it's doing this, but it must have something to do with postback. If it is a postback problem, is there a way to store the dropdown selection and restore the selection after re-load? Please don't suggest using AJAX or update panels, as we aren't allowed. Here is my asp code:
<p>
<asp:DropDownList ID="ddlProjects" runat="server"
onselectedindexchanged="ddlProjects_SelectedIndexChanged"
AutoPostBack="True" Visible="false" >
</asp:DropDownList>
</p>
<asp:DropDownList ID="ddlChargeCodes" runat="server" AutoPostBack="true"
onselectedindexchanged="ddlChargeCodes_SelectedIndexChanged" Visible="false">
</asp:DropDownList>
<p>
and the C# code behind:
protected void Page_Load(object sender, EventArgs e)
{
try
{
if (!IsPostBack)
{
LoadProjectsDropDown();
}
//Rest of Pageload Omitted....
// Initial Population of Project Dropdown
protected void LoadProjectsDropDown()
{
try
{ // Populate the Projects Drop Down from Table
ddlProjects.Items.Clear();
ddlProjects.DataSource = Time_Tracker.BLL.ProjectsManager.GetItems();
ddlProjects.DataTextField = "Project_Name";
ddlProjects.DataValueField = "Project_ID";
ddlProjects.DataBind();
ddlProjects.Items.Insert(0, new ListItem("PLEASE SELECT A PROJECT",
"PLEASE SELECT A PROJECT"));
}
catch (Exception ex)
{
Utilities.ErrorLog(ex.Message, ex.GetType().ToString(), ex.StackTrace,
#"Time_Tracker.txt");
}
}
// The Index Change portion of the Project Dropdown, which builds the Charge Code dropdown
protected void ddlProjects_SelectedIndexChanged(object sender, EventArgs e)
{
try
{ // When user selects the Project, Populate Charge Codes for the selected Project
ddlChargeCodes.Visible = true;
if (!string.IsNullOrEmpty(ddlProjects.SelectedValue))
{
ddlChargeCodes.Items.Clear();
ddlChargeCodes.DataSource = Time_Tracker.BLL.TasksManager.GetChargeCodes
(ddlProjects.SelectedValue);
ddlChargeCodes.DataTextField = "Description";
ddlChargeCodes.DataValueField = "Project_ID";
ddlChargeCodes.DataBind();
ddlChargeCodes.Items.Insert(0, new ListItem("PLEASE SELECT A CHARGE
CODE", "PLEASE SELECT A CHARGE CODE"));
Utilities.Project = Convert.ToInt16(ddlProjects.SelectedValue);
}
}
catch (Exception ex)
{
Utilities.ErrorLog(ex.Message, ex.GetType().ToString(), ex.StackTrace, #"Time_Tracker.txt");
}
}
// The Index Change of the Charge Codes Dropdown
protected void ddlChargeCodes_SelectedIndexChanged(object sender, EventArgs e)
{
try
{ // When user selects the Charge Code, it shows a summary and asks for the number of hours
Utilities.Description = Convert.ToString(ddlChargeCodes.SelectedItem);
Utilities.Chargecode = Convert.ToString(ddlChargeCodes.SelectedItem);
lblHoursLabel.Visible = true;
txtHours.Visible = true;
lblConfirmation.Visible = true;
btnStarOver.Visible = true;
btnOK.Visible = true;
lblConfirmation.Text = "Hours on " + Utilities.SelectedDate + " For Charge Code " + Utilities.Description;
}
catch (Exception ex)
{
Utilities.ErrorLog(ex.Message, ex.GetType().ToString(), ex.StackTrace, #"Time_Tracker.txt");
}
}

Answer 1

Did a lot of troubleshooting today. found that upon selecting the chargecode, it would do a pageload without triggering the "change index" event handler. Upon completion of pageload, it would trigger the index change event with the first selection (index 1) selected. Everyone I talked to said it should work the way it is. I finally wrote out the query/databind part of it to populate the dropdown instead of using the stored procedure and it now works. I have included the code change if it will help people in the future.
protected void ddlProjects_SelectedIndexChanged(object sender, EventArgs e)
{
try
{ // When user selects the Project, Populate Charge Codes for the selected Project
ddlChargeCodes.Visible = true;
if (!string.IsNullOrEmpty(ddlProjects.SelectedValue))
{
ddlChargeCodes.Items.Clear();
string strConn = Time_Tracker.DAL.DBUtils.SqlConnectionString;
SqlConnection con = new SqlConnection(strConn);
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "SELECT Charge_Code, Charge_Code + ' - ' + Description AS Description FROM [Time_Tracker].[dbo].[Tasks] WHERE Inactive = 0 AND Project_ID = " + ddlProjects.SelectedValue;
DataSet objDs = new DataSet();
SqlDataAdapter dAdapter = new SqlDataAdapter();
dAdapter.SelectCommand = cmd;
con.Open();
dAdapter.Fill(objDs);
con.Close();
if (objDs.Tables[0].Rows.Count > 0)
{
ddlChargeCodes.DataSource = objDs.Tables[0];
ddlChargeCodes.DataTextField = "Description";
ddlChargeCodes.DataValueField = "Charge_Code";
ddlChargeCodes.DataBind();
ddlChargeCodes.Items.Insert(0, "PLEASE SELECT A CHARGE CODE");
}
Utilities.Project = Convert.ToInt16(ddlProjects.SelectedValue);
}
}
catch (Exception ex)
{
Utilities.ErrorLog(ex.Message, ex.GetType().ToString(), ex.StackTrace, #"Time_Tracker.txt");
}
}