С задержкой отображается информация из бд

public void UpdateDBGroups()
        {
            string query = "SELECT group_name FROM [Group] ORDER BY group_name";
 
            OleDbCommand cmd = new OleDbCommand(query, myConnection);
            OleDbDataReader reader = cmd.ExecuteReader();
 
            GroupList.Items.Clear();
            while (reader.Read())
            {
                GroupList.Items.Add(reader[0].ToString());
            }
            this.groupTableAdapter.Fill(this.myDBDataSet.Group);
            reader.Close();
        }

string query = $"DELETE FROM [Group] WHERE group_name = '{box1.SelectedItem}'";
                OleDbCommand cmd = new OleDbCommand(query, connection);
                cmd.ExecuteNonQuery();

public void UpdateDBGroups()
        {
          string query = "SELECT group_name FROM [Group] ORDER BY group_name";
 
          OleDbCommand cmd = new OleDbCommand(query, myConnection);
 
          GroupList.Items.Clear();
          using (OleDbDataReader reader = cmd.ExecuteReader())
          {
            while (reader.Read())
            {
                GroupList.Items.Add(reader[0].ToString());
            }
            reader.Close();
          }
          this.groupTableAdapter.Fill(this.myDBDataSet.Group);
        }

string name = tb.Text, query = $"INSERT INTO [Group] (ide, group_name) VALUES ({ide},'{name}')";
            OleDbCommand cmd = new OleDbCommand(query, connection);
            cmd.ExecuteNonQuery();
 
            MessageBox.Show("Группа добавлена!");

 string query = $"DELETE FROM [Group] WHERE group_name = '{box1.SelectedItem}'";
                OleDbCommand cmd = new OleDbCommand(query, connection);
                cmd.ExecuteNonQuery();

// добавили в базу
string name = tb.Text, query = $"INSERT INTO [Group] (ide, group_name) VALUES ({ide},'{name}')";
            OleDbCommand cmd = new OleDbCommand(query, connection);
            cmd.ExecuteNonQuery();
 
//добавили в UI
GroupList.Items.Add(name);
MessageBox.Show("Группа добавлена!");