C＃困惑如何在完成工作后结束BackgroundWorker

Question

我正在创建一个程序，其中一部分需要连接到工作sql服务器，检索活动客户帐户列表，然后将该列表显示到组合框中。代码执行在初始加载表单期间应该执行的操作，但是当我尝试从刷新按钮运行后台工作程序时，我收到一条错误消息：

  

此BackgroundWorker当前正忙，无法同时运行多个任务

我很困惑为什么在我看来，代码显然已经到了RunWorkerCompleted方法的末尾。

private void EnterCompletions_Load(object sender, EventArgs e)
    {
        lblcomboBox1Status.Text = "Attempting to download list of active accounts ...";

        backgroundWorker1.RunWorkerAsync();          
    }

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        // *** tblaccts - AID | AName ***
        myConnection.Open();
        SqlCommand myCommand = new SqlCommand("SELECT AID, AName " +
                                              "FROM tblaccts " +
                                              "WHERE Status IS NULL " +
                                              "ORDER BY AID ASC", myConnection);
        SqlDataReader myReader = myCommand.ExecuteReader();

        while (myReader.Read())
        {
            accts_aid.Add(myReader["AID"].ToString());
            accts_aname.Add(myReader["AName"].ToString());
        }

        myConnection.Close();

        for (int i = 0; i < accts_aid.Count; i++) // create a list which contains strings in this format:  "account number | account name"
        {
            accts_string_aid.Add(accts_aid[i] + "  |  " + accts_aname[i]);
        }

        for (int i = 0; i < accts_aname.Count; i++) // create a list which contains strings in this format:  "account name | account number"
        {
            accts_string_name.Add(accts_aname[i] + "  |  " + accts_aid[i]);
        }

        accts_aid.Clear();
        accts_aname.Clear();
    }

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {           
        if (e.Error == null)
        {
            if(rbAid.Checked)
            {
                foreach (string stuff in accts_string_aid) // fill the combobox with the custom display format:  "account number | account name"
                {
                    comboBox1.Items.Add(stuff);
                }
                aid_or_name = "aid";
            }

            if(rbName.Checked)
            {
                foreach (string stuff in accts_string_name) // fill the combobox with the custom display format:  "account name | account number"
                {
                    comboBox1.Items.Add(stuff);
                }
                aid_or_name = "name";
            }

            lblcomboBox1Status.Text = "Account list successfully downloaded.";
            comboBox1.Focus();
            comboBox1.DroppedDown = true;               
        }
        else
        {
            lblcomboBox1Status.Text = "Unable to connect to the server.";
        }
    }