ASP.NET/C# SelectedIndexChanged not firing on

Question

I'm trying to set up cascading dropdown lists on a form for HR-related requests, with the positions displayed depending on the department selected. It might help if I already knew what I was doing, but this whole project is my first foray into ASP.NET and C#, so I'm learning as I go. That said, my position dropdown is coded like so:

<asp:ScriptManager ID="SCRMAN_PositionDropdown" runat="server" />
    <asp:DropDownList ID="SEL_Position" tabindex="7" runat="server" AutoPostBack="true">
        <asp:ListItem>Select a Department first</asp:ListItem>
    </asp:DropDownList>
    <span style="font-size:larger;">&larr;</span>If "Other" specify in the Notes box

EDIT: Here's how my Department dropdown is coded after some revision based on @dman2036 pointing out that I'd apparently tied this whole process to the wrong dropdown changing. For some reason the ending tag isn't showing, but it's there. <fsst_custom:DropDownListGrouped ID="SEL_Department" TabIndex="6" runat="server" OnSelectedIndexChanged="SEL_Department_SelectedIndexChanged" required > <%--SCRIPT INSERTS OPTIONS --%> `

The C# code that should be controlling this is as follows (in pertinent part). SEL_Department is populating correctly but for some reason (probably some ludicrous mistake in my scripting) the SelectedIndexChange is not firing. Did I maybe not include some "using" statement or am I calling it incorrectly? Note: I assume it's not firing because changing SEL_Department should at least clear out SEL_Position's "Select a Department First" item.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.DirectoryServices;
using System.Linq;
using System.Management;
using System.Security.Principal;
using System.Text;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;
using FSST;
using FSST.Controls;


public partial class Casino_HR_Request : System.Web.UI.Page
{

#region Constructor

public Casino_HR_Request()
{
    Load += new EventHandler(Page_Load);
}

#endregion

#region Department_And_Position    

protected void SEL_Department_SelectedIndexChanged(object sender, EventArgs e)
{
    SEL_Position.Items.Clear();

    switch(SEL_Department.SelectedValue)
    {
        case "Executive":
            SEL_Position.Items.Add(new ListItem("Select a position", ""));
            SEL_Position.Items.Add(new ListItem("General Manager", "General Manager"));
            SEL_Position.Items.Add(new ListItem("Assistant General Manager", "Assistant General Manager"));
            SEL_Position.Items.Add(new ListItem("Internal Auditor", "Internal Auditor"));
            SEL_Position.Items.Add(new ListItem("Compliance Officer", "Compliance Officer"));
            SEL_Position.Items.Add(new ListItem("Executive Assistant", "Executive Assistant"));
            SEL_Position.Items.Add(new ListItem("Other", "Other"));
            break;
        case "Finance":
            SEL_Position.Items.Add(new ListItem("Select a position", ""));
            SEL_Position.Items.Add(new ListItem("Controller", "Controller"));
            SEL_Position.Items.Add(new ListItem("Assistant Controller", "Assistant Controller"));
            SEL_Position.Items.Add(new ListItem("Cage Manager", "Cage Manager"));
            SEL_Position.Items.Add(new ListItem("Cage Supervisor", "Cage Supervisor"));
            SEL_Position.Items.Add(new ListItem("Cage Cashier", "Cage Cashier"));
            SEL_Position.Items.Add(new ListItem("Count Manager", "Count Manager"));
            SEL_Position.Items.Add(new ListItem("Assistant Count Manager", "Assistant Count Manager"));
            SEL_Position.Items.Add(new ListItem("Count Team", "Count Team"));
            SEL_Position.Items.Add(new ListItem("Senior Staff Accountant", "Senior Staff Accountant"));
            SEL_Position.Items.Add(new ListItem("Accounts Payable", "Accounts Payable"));
            SEL_Position.Items.Add(new ListItem("Accounts Receivable", "Accounts Receivable"));
            SEL_Position.Items.Add(new ListItem("Purchasing", "Purchasing"));
            SEL_Position.Items.Add(new ListItem("Receiving Clerk", "Receiving Clerk"));
            SEL_Position.Items.Add(new ListItem("Senior Accounting Auditor", "Senior Accounting Auditor"));
            SEL_Position.Items.Add(new ListItem("Accounting Auditor", "Accounting Auditor"));
            SEL_Position.Items.Add(new ListItem("Other", "Other"));
            break;
    // A BUNCH MORE CASES GO HERE
    }
}
#endregion

#region Page_Load

void Page_Load(object sender, EventArgs e)
{   
    //----------STATUS CHANGE MENU OPTIONS----------
    SEL_StatusChange.Items.Add(NewGroupedListItem("New Hire", "New Hire", "Onboard or Separate"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Separation", "Separation", "Onboard or Separate"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Position Change", "Position Change", "Changes in employment"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Add 2nd- or 3rd-Rate", "Add 2nd- or 3rd-Rate", "Changes in Employment"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Remove 2nd- or 3rd-Rate", "Remove 2nd- or 3rd-Rate", "Changes in employment"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Add listed access", "Add listed access", "Change in needs only"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Remove listed access", "Remove listed access", "Change in needs only"));
    //----------DEPARTMENT MENU OPTIONS----------
    SEL_Department.Items.Add(NewGroupedListItem("", "Department Name", ""));
    SEL_Department.Items.Add(NewGroupedListItem("Executive", "Executive", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Finance", "Finance", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Food and Beverage", "Food and Beverage", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Gaming Commission", "Gaming Commission", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Gas Stations", "Gas Stations", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Hotel", "Hotel", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Human Resources", "Human Resources", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("IT", "IT", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Maintenance", "Maintenance", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Marketing", "Marketing", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Player's Club", "Player's Club", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Porters", "Porters", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Security", "Security", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Slots", "Slots", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Surveillance", "Surveillance", "Select a department"));
    SEL_Department.Items.Add(NewGroupedListItem("Table Games", "Table Games", "Select a department"));
}

protected ListItem NewGroupedListItem(string value, string text, string group)
{
    ListItem li = new ListItem(value, text);
    li.Attributes.Add("optgroup", group);
    return li;
}

#endregion

//TWO MORE REGIONS NOT RELEVANT TO THIS GO HERE
}

Here's the code for DropdownListGrouped , which a friend sent me and I just incorporated as he told me.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

    namespace FSST.Controls
    {

        /// <summary>
        /// Provides options for grouping list items.
        /// </summary>
        /// <remarks>
        /// Much came from here:
        /// http://stackoverflow.com/questions/130020/dropdownlist-control-with-optgroups-for-asp-net-webforms
        /// </remarks>
        public class DropDownListGrouped : System.Web.UI.WebControls.DropDownList
        {
            const string OptionGroupTag = "optgroup";
            const string OptionTag = "option";

            #region DataGroupingField

            public string DataGroupingField
            {
                get
                {
                    object o = ViewState["DataGroupingField"];
                    return (o == null) ? "" : (string)o;
                }
                set
                {
                    ViewState["DataGroupingField"] = value;
                }
            }

            #endregion

            #region PerformDataBinding

            protected override void PerformDataBinding(System.Collections.IEnumerable dataSource)
            {
                base.PerformDataBinding(dataSource);
                if (DataGroupingField.Length == 0)
                    return;

                // Go back through the data source and assign the attributes

                // We know the items were added to the end, so just work through them
                if (dataSource != null)
                {
                    ICollection collection = dataSource as ICollection;
                    int startIndex = 0;
                    if (collection != null)
                        startIndex = this.Items.Count - collection.Count;

                    string dataGroupingField = DataGroupingField;
                    foreach (object current in dataSource)
                        Items[startIndex++].Attributes.Add(OptionGroupTag, DataBinder.GetPropertyValue(current, DataGroupingField, null));
                }
            }

            #endregion

            #region RenderContents

            protected override void RenderContents(System.Web.UI.HtmlTextWriter writer)
            {
                ListItemCollection items = this.Items;
                int count = items.Count;
                string tag;
                string optgroupLabel;
                if (count > 0)
                {
                    bool flag = false;
                    string prevOptGroup = null;
                    for (int i = 0; i < count; i++)
                    {
                        tag = OptionTag;
                        optgroupLabel = null;
                        ListItem item = items[i];
                        if (item.Enabled)
                        {
                            if (item.Attributes != null && item.Attributes.Count > 0 && item.Attributes[OptionGroupTag] != null)
                            {
                                optgroupLabel = item.Attributes[OptionGroupTag];

                                if (prevOptGroup != optgroupLabel)
                                {
                                    if (prevOptGroup != null)
                                        writer.WriteEndTag(OptionGroupTag);
                                    writer.WriteBeginTag(OptionGroupTag);
                                    if (!string.IsNullOrEmpty(optgroupLabel))
                                        writer.WriteAttribute("label", optgroupLabel);
                                    writer.Write('>');
                                }
                                item.Attributes.Remove(OptionGroupTag);
                                prevOptGroup = optgroupLabel;
                            }
                            else
                            {
                                if (prevOptGroup != null)
                                    writer.WriteEndTag(OptionGroupTag);
                                prevOptGroup = null;
                            }

                            writer.WriteBeginTag(tag);
                            if (item.Selected)
                            {
                                if (flag)
                                    this.VerifyMultiSelect();
                                flag = true;
                                writer.WriteAttribute("selected", "selected");
                            }
                            writer.WriteAttribute("value", item.Value, true);
                            if (item.Attributes != null && item.Attributes.Count > 0)
                                item.Attributes.Render(writer);
                            if (optgroupLabel != null)
                                item.Attributes.Add(OptionGroupTag, optgroupLabel);
                            if (this.Page != null)
                                this.Page.ClientScript.RegisterForEventValidation(this.UniqueID, item.Value);

                            writer.Write('>');
                            HttpUtility.HtmlEncode(item.Text, writer);
                            writer.WriteEndTag(tag);
                            writer.WriteLine();
                            if (i == count - 1 && prevOptGroup != null)
                                writer.WriteEndTag(OptionGroupTag);
                        }
                    }
                }
            }

            #endregion

            #region SaveViewState

            protected override object SaveViewState()
            {
                object[] state = new object[this.Items.Count + 1];
                object baseState = base.SaveViewState();
                state[0] = baseState;
                bool itemHasAttributes = false;

                for (int i = 0; i < this.Items.Count; i++)
                {
                    if (this.Items[i].Attributes.Count > 0)
                    {
                        itemHasAttributes = true;
                        object[] attributes = new object[this.Items[i].Attributes.Count * 2];
                        int k = 0;

                        foreach (string key in this.Items[i].Attributes.Keys)
                        {
                            attributes[k] = key;
                            k++;
                            attributes[k] = this.Items[i].Attributes[key];
                            k++;
                        }
                        state[i + 1] = attributes;
                    }
                }

                if (itemHasAttributes)
                    return state;
                return baseState;
            }

            #endregion

            #region LoadViewState

            protected override void LoadViewState(object savedState)
            {
                if (savedState == null)
                    return;

                if (!(savedState.GetType().GetElementType() == null) &&
                    (savedState.GetType().GetElementType().Equals(typeof(object))))
                {
                    object[] state = (object[])savedState;
                    base.LoadViewState(state[0]);

                    for (int i = 1; i < state.Length; i++)
                    {
                        if (state[i] != null)
                        {
                            object[] attributes = (object[])state[i];
                            for (int k = 0; k < attributes.Length; k += 2)
                            {
                                this.Items[i - 1].Attributes.Add
                                    (attributes[k].ToString(), attributes[k + 1].ToString());
                            }
                        }
                    }
                }
                else
                {
                    base.LoadViewState(savedState);
                }
            }

            #endregion
        }
    }

Answer 1

You are re-populating the lists in Page_Load which is resetting the selected index. I would move that logic to a separate method and only call if if the request is not a post-back:

void Page_Load(object sender, EventArgs e)
{
    if(!Page.IsPostBack)
        BindLists();   
}

void BindLists()
{
    //----------STATUS CHANGE MENU OPTIONS----------
    SEL_StatusChange.Items.Add(NewGroupedListItem("New Hire", "New Hire", "Onboard or Separate"));
    SEL_StatusChange.Items.Add(NewGroupedListItem("Separation", "Separation", "Onboard or Separate"));
    // etc.
}

UI Event handling in ASP.NET takes some practice to get right since every post-back is a completely new web request. It's different than WinForms where everything remains in memory. The entire page is re-rendered with every post back, and you need to handle state appropriately.