using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Xml.Serialization;

namespace Login_Form
{
    public class xmlSave
    {
        public static void SaveData(object IClass, string filename)
        {
            StreamWriter writer = null;
            try
            {
                XmlSerializer xml = new XmlSerializer((IClass.GetType()));
                writer = new StreamWriter(filename);
                xml.Serialize(writer, IClass);
            }
            finally
            {
                if (writer != null)
                    writer.Close();
                writer = null;
            }
        }
    }

    public class xmlLoad<T>
    {
        public static Type type;

        public xmlLoad()
        {
            type = typeof(T);
        }

        public T LoadData(string filename)
        {
            T result;
            XmlSerializer xml = new XmlSerializer(type);
            FileStream fs = new FileStream(filename, FileMode.Open,     FileAccess.Read, FileShare.Read);
            result = (T)xml.Deserialize(fs);
            fs.Close();
            return result;
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using System.Xml.Serialization;

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

        private void button1_Click(object sender, EventArgs e)
        {
            saveFileDialog.InitialDirectory =     @"C:UsersFelixDocumentsvisual studio 2013ProjectsLogin FormLogin     FormbinDebug";
            saveFileDialog.Filter = "xml Files (*.xml)|*.xml";
            saveFileDialog.FilterIndex = 2;
            saveFileDialog.RestoreDirectory = true;

            if(saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                User user = new User();
                user.FName = textBox1.Text;
                user.LName = textBox2.Text;
                user.Username = textBox3.Text;
                user.Email = textBox4.Text;
                user.Password = textBox5.Text;
                xmlSave.SaveData(user, saveFileDialog.FileName);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            User user = new User();
            xmlLoad<User> loadUser = new xmlLoad<User>();

            user = loadUser.LoadData("test.xml");
            textBox1.Text = user.FName;
            textBox2.Text = user.LName;
            textBox3.Text = user.Username;
            textBox4.Text = user.Email;
            textBox5.Text = user.Password;
        }
    }

    public class User
    {
        private string fName;
        private string lName;
        private string username;
        private string email;
        private string password;

        public string FName
        {
            get { return fName; }
            set { fName = value; }
        }

        public string LName
        {
            get { return lName; }
            set { lName = value; }
        }

        public string Username
        {
            get { return username; }
            set { username = value; }
        }

        public string Email
        {
            get { return email; }
            set { email = value; }
        }

       public string Password
        {
            get { return password; }
            set { password = value; }
        }
    }
}