C# Files and Streams

Dear C# Programmers,

I want to create a project which writes record into file, but the program throws a FormatException when I clickEnter button... Catch hadles SerializationException and shows my specified message. Now I wanna know what happen during serialization???

save as button   normally works as well as Exit button. So first I create file with (.dat) extension  and then I want to write records into file, but shows "Error Writing to File" Message

in any case, my OS is win 7 and using VS 2010

Pls. help me

The Following is my cod

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.IO;

using BankUIForm;

namespace CreateFileForm3
{
    public partial class Form2 : BankUIForm.BankUIForm
    {

        // serializes Record in binary format
        BinaryFormatter formatter = new BinaryFormatter();


        // stream through which serializable data is written to file
        private FileStream output;


        public Form2()
        {
            InitializeComponent();
        }


        private void saveButton_Click(object sender, EventArgs e)
        {
            SaveFileDialog fileChooser = new SaveFileDialog();
            DialogResult result = fileChooser.ShowDialog();

            string fileName; // name of file to save data

            // allow user to create file
            fileChooser.CheckFileExists = false;


            // exit event handler if user clicked "Cancel"
            if (result == DialogResult.Cancel)
                return;

            // get specified file name
            fileName = fileChooser.FileName;

            if (fileName == "" || fileName == null)
            {
                MessageBox.Show("invalid file Name", "Error",
                    MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

            else
            {
                // save file via FileStream if user specified valid file
                try
                {
                    output = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.Write);

                    // disable Save button and enable Enter button
                    saveButton.Enabled = false;
                    enterButton.Enabled = true;
                }

                // handle exception if file does not exist
                catch (FileNotFoundException)
                {
                    MessageBox.Show("File Does Not Exist", "Error",
                        MessageBoxButtons.OK, MessageBoxIcon.Error);
                }

            }
        }

        private void enterButton_Click(object sender, EventArgs e)
        {
            string[] values = GetTextBoxValues();

            // Record containing TextBox values to serialize
            Record record = new Record();


            // determine whether TextBox account field is empty
            if (values[(int)textBoxIndices.Account] != "")
            {
                // store TextBox values in Record and serialize Record
                try
                {
                    // get account number value from TextBox
                    int AccountNumber = Int32.Parse(
                        values[(int)textBoxIndices.Account]);

                    // determine whether accountNumber is valid
                    if (AccountNumber > 0)
                    {

                        // store TextBox fields in Record
                        record.Account = AccountNumber;
                        record.FirstName = values[(int)textBoxIndices.First];
                        record.LastName = values[(int)textBoxIndices.Last];
                        record.Balance = double.Parse(values[(int)textBoxIndices.Balance]);

                        // write Record to FileStream (serialize object)
                        formatter.Serialize(output, record);
                    }

                    else
                    {
                        // Notify user if invalid number
                        MessageBox.Show("Invalid Account Number", "Error",
                            MessageBoxButtons.OK, MessageBoxIcon.Error);

                    }
                }

                // notify user if error occurs in serialization
                catch (SerializationException)
                {
                    MessageBox.Show("Error Writing to File", "Error",
                        MessageBoxButtons.OK, MessageBoxIcon.Error);
                }

                // notify user if error occurs regarding parameter format
                catch (FormatException)
                {
                    MessageBox.Show("Invalid Format", "Error",
                        MessageBoxButtons.OK, MessageBoxIcon.Error);
                }

            }

            ClearTextBox(); // clear TextBox values

        }


        // invoked when user clicks Exit button
        private void exitButton_Click(object sender, EventArgs e)
        {
            // determine whether file exists
            if (output != null)
            {
                try
                {
                    output.Close();
                }

                    // notify user of error closing file
                catch (IOException)
                {
                    MessageBox.Show("Cannot close file", "Error",
                        MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }

            Application.Exit();


        }  // end method exitButton_Click


    }
}