How to use ASP.NET 4.0 time picker user control using C# ?

WebUserControl1.ascx

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="WebUserControl1.ascx.cs" Inherits="TimePickerDemo1.CustomControls.WebUserControl1" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<link href="TimeExtender.css" rel="stylesheet" type="text/css" />
<asp:ImageButton ID="ibtnShowPicker" runat="server"   ImageUrl="btnTimeExtenderBlue.gif"
    OnClientClick="return false;"
    CssClass="btnTimeExtender_Style" />
    <div>
    <asp:PopupControlExtender ID="PopupControlExtender_Time"  PopupControlID="datalistTimes"        
        CommitProperty="value" 
        Position="Bottom"  runat="server">
    </asp:PopupControlExtender>

    
     <asp:DataList ID="datalistTimes"       
        RepeatDirection="Horizontal"
        RepeatColumns="4"
        OnItemDataBound="datalistTimes_OnItemDataBound"
        CssClass="Datalist_ControlStyle"
        HeaderStyle-CssClass="Datalist_HeaderStyle"
        ItemStyle-CssClass="Datalist_ItemStyle"
        runat="server" >

        <HeaderTemplate> 
            <div class="Datalist_HeaderLeft">      
            </div>
            <div class="Datalist_HeaderCenter">
            <asp:LinkButton ID="lbtnHeaderTime"
                OnCommand="lbtnHeaderTime_OnCommand"
                ToolTip="click to select current time"
                runat="server" />
            </div>
            <div class="Datalist_HeaderRight">
            <asp:LinkButton ID="lbtnHeaderAM" 
                Text="AM" 
                OnCommand="lbtnHeaderAM_OnCommand"  
                CommandArgument="am"
                runat="server" />
            <asp:LinkButton ID="lbtnHeaderPM" 
                Text="PM" 
                OnCommand="lbtnHeaderPM_OnCommand"
                CommandArgument="pm"
                runat="server" />
            </div>          
        </HeaderTemplate>
       
        <ItemTemplate>
        <asp:LinkButton ID="lbtnTime" 
            CommandName="second" 
            OnCommand="lbtnTime_Onclick" 
            CommandArgument='<%# Eval("Time") %>' 
            Text='<%# Eval("Time") %>'
            runat="server"/>         
        </ItemTemplate>
    </asp:DataList>   

</div>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text.RegularExpressions;
using System.Data;
using System.Collections;
using System.Globalization;

namespace TimePickerDemo1.CustomControls
{
    public partial class WebUserControl1 : System.Web.UI.UserControl
    {
        protected void Page_Init(object sender, System.EventArgs e)
        {
            // set property defaults based on selected properties to fix conflicts
            FixPropertyConflicts();
            // validate selected date
            ValidateSelectedTime();
            // load times
            BindDataSource();
            // show or hide the picker button that appears beside parent control
            ShowOrHideTimePickerButton();
        }
        private void ShowOrHideTimePickerButton()
        {
            bool bolShowButton = System.Convert.ToBoolean(ViewState["ShowButton"]);
            if (bolShowButton)
            {
                this.ibtnShowPicker.Visible = true;
                this.PopupControlExtender_Time.TargetControlID = this.ibtnShowPicker.UniqueID;
                // set popup position
                this.PopupControlExtender_Time.OffsetX = (7 + GetParentControlWidth()) * (-1);
            }
            else
            {
                this.ibtnShowPicker.Visible = false;
                // must set new target control
                this.PopupControlExtender_Time.TargetControlID = System.Convert.ToString(ViewState["TargetControlID"]);
            }
        }
        private int GetParentControlWidth()
        {
            string strTargetControlID = System.Convert.ToString(ViewState["TargetControlID"]);
            Control objParentControl = (Control)this.Parent.FindControl(strTargetControlID);
            if (objParentControl == null)
                return 50;
            string strControlType = objParentControl.GetType().ToString();
            int i = 0;
            if (strControlType.ToLower().Contains("textbox"))
            {
                i = 1;
            }
            else
            {
                i = 2;
            }
            switch (i)
            {
                case 1:
                    {
                        TextBox textboxParent = (TextBox)objParentControl;
                        return System.Convert.ToInt32(textboxParent.Width.Value);
                    }

                case 2:
                    {
                        Label lblParent = (Label)objParentControl;
                        return System.Convert.ToInt32(lblParent.Width.Value);
                    }
            }
            return 50;
        }

        private void BindDataSource()
        {
            //   datalistTimes.
            this.datalistTimes.DataSource = CreateDataSource();
            this.datalistTimes.DataBind();
        }
        private ICollection CreateDataSource()
        {
            // Create time data for the DataList control.
            DataTable dt = new DataTable();
            DataRow dr;
            // Define the columns of the table.
            dt.Columns.Add(new DataColumn("Time", typeof(string)));
            // Populate the table with sample values.
            int intMinuteIncrement = Convert.ToInt32(ViewState["MinuteIncrement"]);
            if (intMinuteIncrement == 0)
                intMinuteIncrement = 30;
            // 24 hour clock or 12 hour clock
            int intMaxTime = 720 - intMinuteIncrement;
            string strAMorPM = " " + SelectAMorPM();
            // show am and pm
            if (System.Convert.ToBoolean(ViewState["ShowAMandPM"]))
            {
                intMaxTime = 1440 - 1; // don't show last time
                strAMorPM = " am";
            }
            // show 24 hour clock
            string strColon = ":";
            string strHoursFormat = "{0:#0}";
            if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
            {
                intMaxTime = 1440 - 1; // don't show last time
                strAMorPM = "";
                strHoursFormat = "{0:00}";
                if (!System.Convert.ToBoolean(ViewState["Show24HourClockColon"]))
                    strColon = "";
            }
            else if (System.Convert.ToBoolean(ViewState["ShowLeadingZeros"]))
                strHoursFormat = "{0:00}";
            // populate times
            int intHours = 0;
            int intMins = 0;
            for (int intTime = 0; intTime <= intMaxTime; intTime += intMinuteIncrement)
            {
                if (intTime == 0 | intTime % 60 == 0)
                {
                    // reset mins
                    intMins = 0;
                    // add hours
                    if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
                        // 24 hour clock
                        intHours = intTime / 60;
                    else
                    {
                        // 12 hour clock
                        intHours = intTime / 60;
                        if (System.Convert.ToBoolean(ViewState["ShowAMandPM"]) & intHours > 11)
                        {
                            strAMorPM = " pm";
                            if (intHours > 12)
                                intHours = intHours - 12;
                        }
                        if (intHours == 0)
                            intHours = 12;
                    }
                    // add row
                    string timeHours = string.Format(strHoursFormat + strColon + "{1:00}", intHours, 0) + strAMorPM;
                    dr = dt.NewRow();
                    dr[0] = timeHours;
                    dt.Rows.Add(dr);
                }
                else
                {
                    // add minutes
                    intMins += intMinuteIncrement;
                    string timeMinutes = string.Format(strHoursFormat + strColon + "{1:00}", intHours, intMins) + strAMorPM;
                    dr = dt.NewRow();
                    dr[0] = timeMinutes;
                    dt.Rows.Add(dr);
                }
            }
            // return dataview
            DataView dv = new DataView(dt);
            return dv;
        }



        protected void Page_Load(object sender, EventArgs e)
        {
            // PopupControlExtender_Time

        }
        private void FixPropertyConflicts()
        {
            // set defaults
            if (ViewState["ShowButton"] == null)
                ViewState["ShowButton"] = "false";
            if (ViewState["SelectedTime"] == null)
                ViewState["SelectedTime"] = "";
            if (ViewState["Show24HourClock"] == null)
                ViewState["Show24HourClock"] = "false";
            if (ViewState["ShowLeadingZeros"] == null)
                ViewState["ShowLeadingZeros"] = "false";
            if (ViewState["MinuteIncrement"] == null)
                ViewState["MinuteIncrement"] = "30";
            if (ViewState["Show24HourClockColon"] == null)
                ViewState["Show24HourClockColon"] = "false";
            // fix 24 hour clock conflicts
            if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
            {
                ViewState["ShowAMandPM"] = "false";
                ViewState["ShowLeadingZeros"] = "true";
            }
            // fix 12 hour clock conflicts and set defaults
            if (!System.Convert.ToBoolean(ViewState["Show24HourClock"]))
            {
                ViewState["Show24HourClockColon"] = "false";
                if (ViewState["ShowAMandPM"] == null)
                    ViewState["ShowAMandPM"] = "true";
            }
            // Increment must be 5,10,15...
            int intIncrement = System.Convert.ToInt32(ViewState["MinuteIncrement"]);
            if (intIncrement > 60)
                ViewState["MinuteIncrement"] = "60";
            if (intIncrement < 5)
                ViewState["MinuteIncrement"] = "30";
            if (intIncrement % 5 > 0)
                ViewState["MinuteIncrement"] = "30";

        }
        protected void datalistTimes_OnItemDataBound(object sender, DataListItemEventArgs e)
        {
            // header
            if (e.Item.ItemType == ListItemType.Header)
            {
                LinkButton objlblTime = (LinkButton)e.Item.FindControl("lbtnHeaderTime");
                if (objlblTime != null)
                {
                    string strCurrTime = DateTime.Now.ToShortTimeString();
                    if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
                        strCurrTime = Format24HourTime(strCurrTime);
                    objlblTime.Text = SetLeadingZero(strCurrTime);
                    objlblTime.BorderWidth = 0; // could not get working in CSS so do it here
                }
                // set AM button
                LinkButton objlbtnHeader = (LinkButton)e.Item.FindControl("lbtnHeaderAM");
                if (objlbtnHeader != null)
                {
                    if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
                        HideAMorPMButton(objlbtnHeader);
                    else
                        // show both buttons and select one
                        SetButtonsAMorPM(objlbtnHeader, "am");
                }
                // set PM buton
                objlbtnHeader = (LinkButton)e.Item.FindControl("lbtnHeaderPM");
                if (objlbtnHeader != null)
                {
                    if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
                        // hide buttons if displaying 24 hour clock
                        HideAMorPMButton(objlbtnHeader);
                    else
                        // show both buttons and select one
                        SetButtonsAMorPM(objlbtnHeader, "pm");
                }
            }
            // can set selected time here - not used
            // need routine to check which time is closest to interval time
            if (e.Item.ItemType == ListItemType.Item | e.Item.ItemType == ListItemType.AlternatingItem)
            {
                LinkButton objlbtnItem = (LinkButton)e.Item.FindControl("lbtnTime");
                if (objlbtnItem != null)
                {
                    if (Format24HourTime(objlbtnItem.Text) == Format24HourTime(System.Convert.ToString(this.ViewState["SelectedTime"])))
                    {
                    }
                    else
                    {
                    }
                }
            }
        }
        protected void lbtnHeaderTime_OnCommand(object sender, CommandEventArgs e)
        {
            // set to current time
            string strCurrTime = DateTime.Now.ToShortTimeString();
            if (System.Convert.ToBoolean(this.ViewState["Show24HourClock"]))
                strCurrTime = Format24HourTime(strCurrTime);
            // hide the popup and return the time
            CommitTime(strCurrTime);
        }
        private void CommitTime(string strSelectedTime)
        {
            if (System.Convert.ToBoolean(this.ViewState["ShowButton"]))
                SetParentControlValue(strSelectedTime);
            this.PopupControlExtender_Time.Commit(strSelectedTime);
        }
        protected void lbtnHeaderAM_OnCommand(object sender, CommandEventArgs e)
        {
            this.ViewState["SelectedTimeAMorPM"] = "am";
            LinkButton myButton = sender as LinkButton;
            SetButtonsAMorPM(myButton, "am");
            // must set Selected time to am to refresh datasource
            this.ViewState["SelectedTime"] = GetTimePart() + " am";
            BindDataSource();
        }
        protected void lbtnHeaderPM_OnCommand(object sender, CommandEventArgs e)
        {
            this.ViewState["SelectedTimeAMorPM"] = "pm";
            LinkButton btn = sender as LinkButton;
            SetButtonsAMorPM(btn, "pm");
            // must set Selected time to pm to refresh datasoure
            this.ViewState["SelectedTime"] = GetTimePart() + " pm";
            BindDataSource();
        }
        //private void SetButtonsAMorPM(object sender, string p)
        //{
        //    throw new NotImplementedException();
        //}
        protected void lbtnTime_Onclick(object sender, CommandEventArgs e)
        {
            string strSelectedValue = e.CommandArgument.ToString().ToUpper();
            CommitTime(strSelectedValue);
        }
          private void SetParentControlValue(string strSelectedValue)
    {
        // get parent control
        string strTargetControlID = System.Convert.ToString(this.ViewState["TargetControlID"]);
        Control objParentControl = (Control)this.Parent.FindControl(strTargetControlID);
        // get type of control
        string strType = objParentControl.GetType().ToString();
              int i=0;
              if(strType.ToLower().Contains("textbox"))
              {
                  i=1;
              }
              else
              {
                   i=2;
              }
        switch (i)
        {
            case 1:
                {
                    TextBox textboxParent = (TextBox)objParentControl;
                    textboxParent.Text = strSelectedValue;
                    break;
                }

            case 2:
                {
                    Label lblParent = (Label)objParentControl;
                    lblParent.Text = strSelectedValue;
                    break;
                }
        }
    }

        private void SetButtonsAMorPM(LinkButton objlbtnHeader, string strAMorPM)
        {
            string strTime = "";
            if (System.Convert.ToBoolean(this.ViewState["ShowAMandPM"]))
            {
                // hide button if displaying am and pm
                objlbtnHeader.BorderWidth = 0;
                objlbtnHeader.Visible = false;
            }
            else
                // show both buttons and select one
                if (SelectAMorPM(strTime) == strAMorPM)
                    objlbtnHeader.BorderWidth = 1;
                else
                    objlbtnHeader.BorderWidth = 0;
        }
        private void HideAMorPMButton(LinkButton objlbtnHeader)
        {
            objlbtnHeader.Visible = false;
        }
        private string SetLeadingZero(string strTime)
        {
            if (System.Convert.ToBoolean(this.ViewState["Show24HourClock"]))
                return strTime;
            if (!System.Convert.ToBoolean(this.ViewState["ShowLeadingZeros"]))
            {
                if (strTime.Substring(0, 1) == "0")
                    return " " + strTime.Substring(1);
            }
            return strTime;
        }
        protected bool CheckDate(String date)
        {
            DateTime Temp;


            if (DateTime.TryParse(date, out Temp) == true)
                return true;
            else
                return false;
        }
        private void ValidateSelectedTime()
        {
            string strSelectedTime = System.Convert.ToString(ViewState["SelectedTime"]);
            // first validate the time entered - set to empty string if not valid
            if (!CheckDate(strSelectedTime))
            try
            {

               // DateTime dt = DateTime.Parse(strSelectedTime);
                this.ViewState["SelectedTime"] = "";
                //return true;
                return;
            }
            catch
            {

                //return false;

            }
                
           
            // Format time
            if (System.Convert.ToBoolean(ViewState["Show24HourClock"]))
                this.ViewState["SelectedTime"] = Format24HourTime(strSelectedTime);
            else
            {
                this.ViewState["SelectedTime"] = Format12HourTime(strSelectedTime);
                this.ViewState["SelectedTimeAMorPM"] = SelectAMorPM(strSelectedTime);
            }
        }
        private string Format12HourTime(string strTime)
        {
            strTime = string.Format("{00:00}", strTime);
            strTime = Regex.Replace(strTime, "[^1234567890]", "");
            if (strTime.Length < 4)
                strTime = "0" + strTime;
         //   Response.Write(strTime);
            DateTime DT = DateTime.ParseExact(strTime.ToString(),"HHmm", System.Globalization.CultureInfo.InvariantCulture);
            string[] formats = new string[] { "hhmm" };
            DateTime dt = DateTime.ParseExact(DT.ToString(), formats,
                                                System.Globalization.CultureInfo.InvariantCulture,
                                                System.Globalization.DateTimeStyles.AdjustToUniversal);
            return dt.ToString("hh:mm tt");
        }
        private string Format24HourTime(string strTime)
        {
            string strTimeOnly = GetTimePart(strTime);
            if (strTime.ToLower().Contains("pm"))
            {
                // convert to 24 hour clock
                int intHours = System.Convert.ToInt32(strTimeOnly.Substring(0, 2));
                intHours += 12;
                strTimeOnly = System.Convert.ToString(intHours).PadLeft(2, '0') + strTimeOnly.Substring(2);
            }
            return strTimeOnly;
        }
        private string SelectAMorPM(string strTime = "")
        {
            string strSelectedTime = System.Convert.ToString(ViewState["SelectedTime"]);
            if (strTime != "")
                strSelectedTime = strTime.ToLower();
            if (strSelectedTime.ToLower().Contains("am"))
                return "am";
            else
                return "pm";
        }
        private string GetTimePart(string strTime = "")
        {
            string strSelectedTime = System.Convert.ToString(ViewState["SelectedTime"]).ToLower();
            if (strTime != "")
                strSelectedTime = strTime.ToLower();
            strSelectedTime = strSelectedTime.Replace("am", "").Trim();
            strSelectedTime = strSelectedTime.Replace("pm", "").Trim();
            int intLength = 5;
            if (System.Convert.ToBoolean(ViewState["Show24HourClock"]) & !System.Convert.ToBoolean(ViewState["Show24HourClockColon"]))
            {
                // no colon
                strSelectedTime = strSelectedTime.Replace(":", "");
                intLength = 4;
            }
            // pad with leading zeros
            if (strSelectedTime.Length < intLength)
                strSelectedTime = "0" + strSelectedTime;
            return strSelectedTime;
        }
    }
}

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeBehind="Default.aspx.cs" Inherits="TimePickerDemo1._Default" %>
    
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>
<%@ Register Src="CustomControls/WebUserControl1.ascx" TagName="TimeExtender" TagPrefix="cc1" %>

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
 <link href="Styles/TimePicker.css" rel="Stylesheet" type="text/css" />
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
<asp:ScriptManager ID="ScriptManager1" runat="server" />

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>

<div class="divMainContainer">
    <h3>Test Time Picker Extender</h3>

    <div class="divSameLine">

        <!-- Start Time - Extender using properties -->
        <asp:Label ID="lblStartTime" 
            Text="Start Time:" 
            AssociatedControlID="txtTime" 
            runat="server" />
        <asp:TextBox ID="txtTime" Width="100" runat="server" />

        <cc1:TimeExtender ID="TimePicker1" 
            MinuteIncrement="15" 
            TargetControlID="txtTime"
            ShowButton="false" 
            ShowAMandPM="false"
            Show24HourClock="false"
            ShowLeadingZeros="false"
            runat="server" />

    </div>

    <div class="divSameLine">

        <!-- End Time - Extender with defaults showing am and pm times -->

        <asp:Label ID="lblEndTime" 
            Text="End Time:"
            AssociatedControlID="txtTime" 
            runat="server" />
        <asp:TextBox ID="txtEndTime" Width="100" runat="server" />

        <cc1:TimeExtender ID="timepickerEndTime"
            TargetControlID="txtEndTime"
            ShowAMandPM="true"
            ShowButton="true"            
            runat="server" />

    </div>
    <div class="divClearFloat"></div>

</div>


</ContentTemplate>
</asp:UpdatePanel>


</asp:Content>

The TargetControlID of 'PopupControlExtender_Time' is not valid. The value cannot be null or empty.