C#, Refresh combo box after adding data

Question

I have read many other questions about this same thing but it seems the answers do not pertain to how I am performing my code. After adding or deleting a record or row of information to my database from the user interface it does not show in the combo boxes until I restart the application. Maybe someone can enlighten me as I am somewhat new to this. Below is my code when clicking the add button.

 private void FBinterface_Load(object sender, EventArgs e)
    {
        txtSerial.Focus();
        try
        {
            connection.Open();

            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            string SerialQuery = "select SerialNumber from Inventory";
            command.CommandText = SerialQuery;

            //TO READ DATA
            OleDbDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                comboSerial.Items.Add(reader["SerialNumber"]);
            }
            connection.Close();
        }
        catch (OleDbException ex)
        {
            MessageBox.Show(ex.Message);
            connection.Close();
        }

 private void btnAdd_Click(object sender, EventArgs e)
    {
        if (!string.IsNullOrEmpty(txtSerial.Text))
        {
            try
            {
                connection.Open();

                OleDbCommand command = new OleDbCommand();
                command.Connection = connection;
                command.CommandText = @"insert into
                    Inventory(SerialNumber,PartNumber,ROnumber,Location)
                    values ('" +
                        txtSerial.Text + "','" +
                        txtPart.Text + "','" +
                        txtRO.Text + "','" +
                        txtLocation.Text + "')";
                //TO READ DATA
                command.ExecuteNonQuery();
                MessageBox.Show("Inventory Added");

                txtPart.Clear();
                txtSerial.Clear();
                txtRO.Clear();
                txtLocation.Clear();

                if (dataGridFB.DataSource != null)
                {
                    dataGridFB.DataSource = null;
                }
                else
                {
                    dataGridFB.Rows.Clear();
                }
                txtSerial.Focus();
                connection.Close(); // CLOSE HERE OR
                                    // YOU CANNOT ENTER RECORDS SIMULTANEOUSLY
            }
            catch (OleDbException ex)
            {
                MessageBox.Show(ex.Message);
                connection.Close();
            }
        }
    }

Answer 1

As a simple fix, you may add the following code snippet before the line connection.Close() in the btnAdd_Click event handler:

            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            string SerialQuery = "select SerialNumber from Inventory";
            command.CommandText = SerialQuery;

            //TO READ DATA
            OleDbDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                comboSerial.Items.Add(reader["SerialNumber"]);
            }

This code snippet will essentially re-bind the ComboBox comboSerial. The same goes to other ComboBoxes if their underlying data is affected by btnAdd_Click procedure. Furthermore, it could be fruitful to create a dedicated procedure (something like ResfreshAllComboBoxes()), place the code similar to the sample snippet above and call it after underlying data change.

Hope this may help.

Answer 2

It's better to put codes in (FBinterface_Load) inside a new method, say FillComboSerial(), and then you have to call that method after inserting each new record right after closing the connection.