One error was occured while writing a programme of sending an email....

using System;
using System.Web;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.Mail;
using System.IO;
using System.Web.UI;


namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            MailMessage objEmail = new MailMessage();
            objEmail.To = convert.System.Net.Mail.MailAddressCollection(txtTo.Text);
            objEmail.From = convert.System.Net.Mail.MailAddressCollection(txtFrom.Text);

            objEmail.Subject = "Test Email";
            objEmail.Body = txtName.Text + ", " + txtComments.Text;
            objEmail.Priority = MailPriority.High;
            SmtpMail.SmtpServer = "smtp.sbcglobal.yahoo.com";
            try
            {
                SmtpMail.Send(objEmail);
                Response.Write("Your Email has been sent sucessfully -  Thank You");
            }
            catch (Exception exc)
            {
                Response.Write("Send failure: " + exc.ToString());
            }

        }



    }


}

<big>MY new code i m giving as belove</big>

using System;
using System.Web;
using System.Drawing;
using System.Text;
using System.Web.UI;
using System.Windows.Forms;
using System.Net.Mail;
using System.IO;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            MailMessage objEmail = new MailMessage();
            objEmail.To = txtTo.Text;
            objEmail.Subject = "Test Email";
            objEmail.From = txtFrom.Text;
            objEmail.Body = txtName.Text + ", " + txtComments.Text;
            SmtpClient send = new SmtpClient("smtp.sbcglobal.yahoo.com");
            
            
            
            objEmail.Priority = MailPriority.High;
            
            try
            {
                send.Send(objEmail);
                label4.Text = "Your Email has been sent sucessfully -  Thank You";
            }
            catch (Exception exc)
            {
                label4.Text = "Send failure: " + exc.ToString();
            }
        }

    }

now error is 
<big>
<pre lang="vb">Error   1   Property or indexer System.Net.Mail.MailMessage.To' cannot be assigned to -- it is read only