private void checkOutButton_Click(object sender, EventArgs e)
        {
            try
            {
                //Declare variables
                int isbn = 0, empID = 0, memID = 0;

                //Set int values
                isbn = SetISBN(isbnTextbox);

                if (isbn != 0)
                {
                    empID = SetEmployeeID(employeeIDTextbox);

                    if (empID != 0)
                    {
                        memID = SetMemberID(memberIDTextbox);
                    }
                }

                //Create table adapters for data validation
                LibraryDataSetTableAdapters.TransactionsTableAdapter transactionsTableAdapter1;
                transactionsTableAdapter1 = new LibraryDataSetTableAdapters.TransactionsTableAdapter();

                LibraryDataSetTableAdapters.BooksTableAdapter booksTableAdapter1;
                booksTableAdapter1 = new LibraryDataSetTableAdapters.BooksTableAdapter();

                //If the book is checked out it will ask for a book that is not and vice versa
                if (booksTableAdapter1.AvailabilityISBN(isbn) == true)
                {
                    MessageBox.Show("Please bring your book back within three weeks." + "\n" +
                                    "Thank You.");
                    transactionsTableAdapter1.InsertQuery(isbn, empID, memID);
                    booksTableAdapter1.UpdateQueryCheckOut(isbn, isbn);
                }
                else
                {
                    MessageBox.Show("Please enter a valid checked in ISBN.");
                }
            }
            //Catches incorrectly formated input
            catch (FormatException)
            {
                MessageBox.Show("A format exception has occured.", "Entry error.");
            }
            //Catches overflow values
            catch (OverflowException)
            {
                MessageBox.Show("An overflow exception has occured.", "Entry error.");
            }
            //Catches all other exceptions
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message + "\n\n" +
                                ex.GetType().ToString() + "\n" +
                                ex.StackTrace, "Exception");
            }
        }
        /*
         * FOCUS LEAVE EVENTS
         */

        //Checks if the ISBN exists after the user leaves the ISBN textbox
        private void isbnTextbox_Leave(object sender, EventArgs e)
        {
            //Declare variables
            int isbn = 0;

            isbn = SetISBN(isbnTextbox);

            //Create table adapters needed to verify if ISBN exists
            LibraryDataSetTableAdapters.BooksTableAdapter booksTableAdapter1;
            booksTableAdapter1 = new LibraryDataSetTableAdapters.BooksTableAdapter();

            //Determines if the ISBN exists
            if (isbn != 0)
            {
                if (booksTableAdapter1.ExistingISBN(isbn) == isbn)
                {
                }
                else
                {
                    MessageBox.Show("Please enter an existing ISBN.");
                    isbnTextbox.Focus();
                }
            }
        }