Create a new Meeting Request in Outlook 2007 using C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Outlook = Microsoft.Office.Interop.Outlook;
using Microsoft.Office.Core;
using Microsoft.Office.Interop.OutlookVIEwCtl;

namespace CreateMeetingRequest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public void Creat_Request()
        {
            try
            {
                Outlook.Application ap = new Microsoft.Office.Interop.Outlook.Application();
                Outlook.AppointmentItem aPPT = ap.CreateItem(Outlook.OlItemType.olAppointmentItem) as   Outlook.AppointmentItem;
                aPPT.Subject = Subjecttxt.Text.ToString().ToString();
                aPPT.MeetingStatus = Outlook.OlMeetingStatus.olMeeting;
                aPPT.Location = Placetxt.Text.Trim().ToString();
                aPPT.Start = DateTime.Parse(Timetxt.Text.Trim().ToString());       
                aPPT.End = DateTime.Parse(Endtimetxt.Text.Trim().ToString());
                Outlo