private void EnterButton_Click(object sender, EventArgs e)
        {
            if (itemTextBox.Text == "")
            {
                MessageBox.Show("Please enter number of item!");
                return;
            }
            if (weightTextBox.Text == "")
            {
                MessageBox.Show("Please enter weight!");
                return;
            }
            double currentWeight = refrigerator.GetCurrentWight(Convert.ToInt32(itemTextBox.Text), Convert.ToDouble(weightTextBox.Text));

            if (currentWeight == 0)
            {
                MessageBox.Show("Your given amount can’t be entered because it will be over flown.");
                return;
            }
            double remainingWeight = refrigerator.GetRemainingWeight();

            currentWeightTextBox.Text   = currentWeight.ToString();
            remainingWeightTextBox.Text = remainingWeight.ToString();
        }