can anyone correct this program ?

using System;
using System.Net;
using System.Net.Mail;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

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

        private void label3_Click(object sender, EventArgs e)
        {

        }

        private void groupBox2_Enter(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void textBox6_TextChanged(object sender, EventArgs e)
        {

        }

        private void groupBox1_Enter(object sender, EventArgs e)
        {

        }

        private void textBox5_TextChanged(object sender, EventArgs e)
        {

        }


        private void btnBrowse_Click(object sender, EventArgs e)
        {
            OpenFileDialog obj = new OpenFileDialog();
            DialogResult res = obj.ShowDialog();
            if (res == DialogResult.OK)
            {
                string fpath;
                fpath = obj.FileName;
                txtAttachments.Text = fpath;
            }
        }

               private void button1_Click(object sender, EventArgs e)
        {
            SmtpClient obj = new SmtpClient();
            NetworkCredential n = new NetworkCredential(txtFrom.Text, "Jeetendra", System.Text.Encoding.UTF8);
            msg.From = m;
            msg.To.Add(txtTo.Text);
            msg.Subject = txtSub.Text;
            msg.Body = txtBody.Text;
            msg.DeliveryNotificationOptions = DeliveryNotificationOptions.OnFailure;
            Attachment a = new Attachment(txtAttachments.Text);
            msg.Attachments.Add(a);
            obj.Send(msg);
            MessageBox.Show("Mail Sent Successfully.....!!!!");
        
        }

        
    }
}

following errors ar coming... Error 1 The best overloaded method match for 'System.Net.NetworkCredential.NetworkCredential(string, string, string)' has some invalid arguments D:\BE630\MailSend\MailSend\Form1.cs 67 35 MailSend 
Error 2 Argument '3': cannot convert from 'System.Text.Encoding' to 'string' D:\BE630\MailSend\MailSend\Form1.cs 67 84 MailSend 
Error 3 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 68 13 MailSend 
Error 4 The name 'm' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 68 24 MailSend 
Error 5 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 69 13 MailSend 
Error 6 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 70 13 MailSend 
Error 7 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 71 13 MailSend 
Error 8 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 72 13 MailSend 
Error 9 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 74 13 MailSend 
Error 10 The name 'msg' does not exist in the current context D:\BE630\MailSend\MailSend\Form1.cs 75 22 MailSend