private void saveTransaction(object sender, EventArgs e)
        {
            var amount     = decimal.ToDouble(amountNumericUpDown.Value);
            var categoryId = int.Parse(categoriesComboBox.SelectedValue.ToString());
            var contactId  = int.Parse(contactsComboBox.SelectedValue.ToString());
            var date       = datePicker.Value;

            if (amount == 0)
            {
                MessageBox.Show(
                    "Please add an amount",
                    "Missing field",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Error);
                return;
            }
            else if (categoryId == 0)
            {
                MessageBox.Show(
                    "Please select a category",
                    "Missing field",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Error);
                return;
            }

            if (isUpdating)
            {
                using (DataBase.DBContainer db = new DataBase.DBContainer())
                {
                    var transaction = (from Transactions in db.Transactions
                                       where Transactions.Id == updatingTransaction.Id
                                       select Transactions).FirstOrDefault();

                    var selectedContact = (from Contacts in db.Contacts
                                           where Contacts.Id == contactId
                                           select Contacts).FirstOrDefault();

                    var selectedCategory = (from Categories in db.Categories
                                            where Categories.Id == categoryId
                                            select Categories).FirstOrDefault();

                    if (transaction != null)
                    {
                        transaction.Amount          = amount;
                        transaction.Category        = selectedCategory;
                        transaction.Contact         = selectedContact;
                        transaction.DateTime        = date;
                        transaction.TransactionType = selectedTransactionType.ToString();
                    }

                    db.SaveChanges();
                }

                this.Close();
            }
            else
            {
                using (DataBase.DBContainer db = new DataBase.DBContainer())
                {
                    var selectedContact = (from Contacts in db.Contacts
                                           where Contacts.Id == contactId
                                           select Contacts).FirstOrDefault();

                    var selectedCategory = (from Categories in db.Categories
                                            where Categories.Id == categoryId
                                            select Categories).FirstOrDefault();

                    DataBase.Transaction transaction = new DataBase.Transaction
                    {
                        Amount          = amount,
                        Category        = selectedCategory,
                        DateTime        = date,
                        Contact         = selectedContact,
                        TransactionType = selectedTransactionType.ToString()
                    };

                    db.Transactions.Add(transaction);
                    db.SaveChanges();
                }

                this.Close();
            }
        }