Question

 private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
    {
        Ontrip _ontrip = new Ontrip(_FNAME);

        string _query2 = "select CContactno from CustomerTbl where CUsername = @USERNAME";
        string _query3 = "select Price from TransactionTypeTble T join PendingTransTbl P ON P.TransType = T.TransType ";
        string _query4 = "select VehicleDescription from DriverTbl D join VehicleSpecTbl V ON D.VehicleType = V.VehicleType";


        SqlConnection _sqlcnn = new SqlConnection("Data Source=MELIODAS;Initial Catalog=WeGo;Integrated Security=True");
        _sqlcnn.Open();
        try
        {
            SqlDataReader _reader = null;
            SqlCommand _cmd = new SqlCommand("Select CFName+' '+CLName from CustomerTbl where CUsername=@USERNAME", _sqlcnn);

            SqlParameter _param = new SqlParameter();
            _param.ParameterName = "@USERNAME";
            _param.Value = dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString();

            _cmd.Parameters.Add(_param);

            _reader = _cmd.ExecuteReader();         //for displaying users name in the label
            while (_reader.Read())
            {
                _ontrip._txtboxUsername.Text = _reader.GetString(0);
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.ToString());
        }

        using (SqlCommand _sqlcmd = new SqlCommand(_query2, _sqlcnn))
        {
            try
            {
                SqlDataReader _reader = null;

                SqlParameter _param = new SqlParameter();
                _param.ParameterName = "@USERNAME";
                _param.Value = dataGridView1.Rows[e.RowIndex].Cells[1].Value.ToString();

                _sqlcmd.Parameters.Add(_param);

                _reader = _sqlcmd.ExecuteReader();         //for displaying users name in the label
                while (_reader.Read())
                {
                    _ontrip._txtboxContact.Text = _reader.GetString(0);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

他们是一种方式让我阅读查询并显示输出，当我运行此代码时，他们的错误是他们已经是一个与命令关联的开放数据阅读器。我应该在文本框中显示多个数据

Answer 1

完成阅读后尝试呼叫关闭。

_reader.Close（）;

Answer 2

 private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
    {
        Ontrip _ontrip = new Ontrip(_FNAME);

        string _query2 = "select CContactno from CustomerTbl where CUsername = @USERNAME";
        string _query3 = "select Price from TransactionTypeTble T join PendingTransTbl P ON P.TransType = T.TransType ";
        string _query4 = "select VehicleDescription from DriverTbl D join VehicleSpecTbl V ON D.VehicleType = V.VehicleType";


        SqlConnection _sqlcnn = new SqlConnection("Data Source=MELIODAS;Initial Catalog=WeGo;Integrated Security=True;MultipleActiveResultSets=True ");
        _sqlcnn.Open();

我添加了MultipleActiveResultSet或MARS

读取多个数据

2 个答案: