How to bubble a user control event in its calling pages or webparts.

This is a user control which contains a Drop Down list and an event


UserControl.ascx contents will be like this : 

<%@ Control Language="C#" AutoEventWireup="true" Inherits="NameSpaceName.ClassName, NameSpaceName, Version=1.0.0.0, Culture=neutral, PublicKeyToken=74a8568657e011e0" %>
.drp-color
{
    color:#7d99c1;
    font-family:Calibri;
    font-size: 8pt;
    width:150px;
}
</style>
<asp:Panel runat="server" ID="mainPanel">
 <asp:DropDownList ID="drpList" runat="server" AutoPostBack="true"  CssClass="drp-color" OnSelectedIndexChanged="drpList_SelectedIndexChanged">
</asp:DropDownList>
</asp:Panel>

UserControl.ascx.cs contents will be like this :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web.UI.WebControls;
using System.Web.UI;
using Microsoft.SharePoint;

namespace NameSpaceName
{
    public partial class ClassName: System.Web.UI.UserControl
    {
        public string TextColumnName { get; set; }
        public string IdColumnName { get; set; }
        public string ListName { get; set; }
     
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                PopulateDropDown();
            }
          
        }

        public void PopulateDropDown()
        {
            try
            {
                DataTable dtResult;
                using (SPSite spSite = new SPSite(SPContext.Current.Site.Url))
                {
                    using (SPWeb spWeb = spSite.OpenWeb())
                    {
                        dtResult = GetListValues(spWeb);
                        drpList.DataSource = dtResult;
                        drpList.DataValueField = this.IdColumnName;
                        drpList.DataTextField = this.TextColumnName;
                        drpList.DataBind();
                        ListItem objItem = new ListItem("View All", "0");
                        drpList.Items.Insert(0, objItem);

                        //if (this.drpList.Items.Count > 0)
                        //{
                        //    this.drpList.Items[0].Selected = true;
                        //    this.OnDropDownListSelectionChanged();
                        //}
                    }
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        public DataTable GetListValues(SPWeb spWeb)
        {
            SPList lstValues = GetList(this.ListName, spWeb);
            if (null != lstValues)
            {
                if (lstValues.ItemCount > 0)
                    return lstValues.Items.GetDataTable();
                else
                    return null;
            }

            return null;
        }

        public SPList GetList(string listName, SPWeb spWeb)
        {
            SPList spList = null;

            if (null != spWeb)
            {
                try
                {
                    spList = spWeb.Lists[listName];
                }
                catch (Exception)
                {
                    spList = null;
                }
            }

            return spList;
        }

        public void drpList_SelectedIndexChanged(object sender, EventArgs e)
        {
            this.OnDropDownListSelectionChanged(sender,e);

        }

        # region Event Section
     
       public delegate void DropDownSelectionDelegate(object sender, EventArgs e);
       protected event DropDownSelectionDelegate drpListselectionChanged;

        public event DropDownSelectionDelegate DropDownListSelectionChanged
        {
            add
            {
                this.drpListselectionChanged += value;
            }
            remove
            {
                this.drpListselectionChanged -= value;
            }
        }
        public virtual void OnDropDownListSelectionChanged(object sender, EventArgs e)
        {
          
            if (this.drpListselectionChanged != null)
                this.drpListselectionChanged(sender,e);
        }
        # endregion
    }
}

Now in the Web part/Page in which you are using this control or want to trap this user control events. In this case its a visual web part (It will be inside another user control) will be like this :
 UserControlABC.ascx :

<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>
<%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register TagPrefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls"
    Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register TagPrefix="Utilities" Namespace="Microsoft.SharePoint.Utilities" Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register TagPrefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>
<%@ Import Namespace="Microsoft.SharePoint" %>
<%@ Register TagPrefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPages"
    Assembly="Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="UserControlA.ascx.cs"
    Inherits="NameSpace.ClassName.UserControlA" %>
<%@ Register Src="/_controltemplates/Project1/SPDropDownControl.ascx" TagPrefix="SAUserControl"
    TagName="SPDropDownList" %>
    <style type="text/css">
        .pnlHorizontal
        {
        width:100%           
        }
    </style>
<asp:Panel runat="server" ID="pnlHorizontal" Visible="false" CssClass="pnlHorizontal">
    <table width="100%">
        <tr>
            <td>
                <font style='font-family: Calibri !important; color: #C0C0C0 !important; font-size: 14pt!important; padding-left:50px; width:30%;'>
                    B :</font>
            </td>
            <td >
                <font style='font-family: Calibri !important; font-size: 8 !important; color: #58443B !important; width:30%;'>
                    D : </font></br>
                <SAUserControl:SPDropDownList runat="server" ID="uscH1" OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                    TextColumnName="Title" IdColumnName="ID" ListName="Channel" />
            </td>
            <td >
                <font style='font-family: Calibri !important; font-size: 8 !important; color: #58443B !important; width:30%;'>
                    H : </font></br><SAUserControl:SPDropDownList runat="server" ID="uscH2"
                        OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                        TextColumnName="Title" IdColumnName="ID" ListName="Topic" />
            </td>
            <td>
                <font style='font-family: Calibri !important; font-size: 8 !important; color: #58443B !important; width:30%; padding-right:100px;'>
                   I : </font></br><SAUserControl:SPDropDownList runat="server" ID="uscH3"
                        OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                        TextColumnName="Name" IdColumnName="ID" ListName="SMEProfile" />
            </td>
        </tr>
    </table>
</asp:Panel>
<asp:Panel runat="server" ID="pnlVertical" Visible="false">
    <table>
        <%--<tr>
            <td class='tc-VerticalSMEHeading'>
                Find eXpert Knowledge by:
            </td>
        </tr>--%>
        <tr>
            <td>
                <font style='font-family: Calibri !important; font-size: 8pt !important; color: black !important;'>
                    A:</font></br><SAUserControl:SPDropDownList runat="server" ID="uscV2" OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                    TextColumnName="Title" IdColumnName="ID" ListName="Channel" />
            </td>
            <td>
        </tr>
        <tr>
            <td>
                <font style='font-family: Calibri !important; font-size: 8pt !important; color: black !important;'>
                    F :</font></br><SAUserControl:SPDropDownList runat="server" ID="uscV1"
                        OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                        TextColumnName="Title" IdColumnName="ID" ListName="Topic" />
            </td>
        </tr>
        <tr>
            <td>
                <font style='font-family: Calibri !important; font-size: 8pt !important; color: black !important;'>
                    E : </font></br><SAUserControl:SPDropDownList runat="server" ID="uscV3"
                        OnDropDownListSelectionChanged="ucListControl1_DropDownListSelectionChanged"
                        TextColumnName="Name" IdColumnName="ID" ListName="SMEProfile" />
            </td>
        </tr>
    </table>
</asp:Panel>


UserControlABC.ascx.cs:

namespace NameSpace
{
    public partial class UserControlABC : UserControl
    {
        public bool Horizontal { get; set; }

        protected void Page_Load(object sender, EventArgs e)
        {
          
        }

        protected void ucListControl1_DropDownListSelectionChanged(object sender, EventArgs e)
        {
            DropDownList ddlCurrent = (DropDownList)sender;
            string selectedID = ddlCurrent.SelectedValue;
            switch (((System.Web.UI.WebControls.ListControl)(sender)).Parent.Parent.ID)
            {
                case "A":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/rets.aspx?ID={0}&Mode=Channel",selectedID));
                    break;
                case "B":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/hyut.aspx?ID={0}&Mode=Topic", selectedID));
                    break;
                case "F":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/kjil.aspx?ID={0}", selectedID));
                    break;
                case "C":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/ghi.aspx?ID={0}&Mode=Channel",selectedID));
                    break;
                case "D":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/mno.aspx?ID={0}&Mode=Topic", selectedID));
                    break;
                case "E":
                    Response.Redirect(SPContext.Current.Web.Url + string.Format("/Pages/abs.aspx?ID={0}", selectedID));
                    break;
            }
        }
    }
}



Now you can trap this event as per cases in which you have used it.