Question

Seeking help from friends

I have loaded 3 tables from database to DataSet using DataReader but I’m unable to bind it to a GridView.

protected void GetStudReport(Object o, EventArgs e)
{
    if (mycon.State != ConnectionState.Open)
    {
        List<string> lstQstn = new List<string>();

        mycon.Open();
        cmd = new MySqlCommand("SELECT * from scord_mark_table where stu_ID=@StID", mycon);
        cmd.Parameters.Add(new MySqlParameter("StID", MySqlDbType.VarChar, 10, "stu_ID"));
        cmd.Parameters["@StID"].Value = drpDnSearch3.SelectedValue;
        MySqlDataReader rdr1 = cmd.ExecuteReader();
        DataSet ds = new DataSet();
        DataTable dtScrTbl = new DataTable("ScoreTable");
        dtScrTbl.Load(rdr1);
        ds.Tables.Add(dtScrTbl);
        rdr1.Close();
        cmd = null;

        int i = 0;
        Dictionary<string, string> dctSub = new Dictionary<string, string>();
        using (DataTableReader dtr = ds.CreateDataReader())
        {
            while (dtr.Read())
            {
                lstQstn.Add(dtr["test_id"].ToString());

                while (i <= lstQstn.Count())
                {
                    cmd = new MySqlCommand("SELECT test_id,subject_id from qution_no_table where test_id='" + lstQstn[i].ToString() + "'", mycon);
                    MySqlDataReader rdr2 = cmd.ExecuteReader();
                    while (rdr2.Read())
                    {
                      dctSub.Add(rdr2["subject_id"].ToString(),rdr2["test_id"].ToString());
                    }
                    rdr2.Close();
                    break;
                }

                i++;


            }
            cmd = null;
        }

        string strTestID="where test_id='";
        i=0;
        foreach (string lst in lstQstn)
        {
            if (i > 0)
            {
                strTestID += @" and test_id='";
            }
            strTestID += lst + @"'";
            i++;
        }


        cmd = new MySqlCommand("SELECT * from qution_no_table " +strTestID+";"+"SELECT * from out_of_mark_table " +strTestID, mycon);

        MySqlDataReader rdr3 = cmd.ExecuteReader();

        DataTable dtQNoTbl = new DataTable("QstNoTable");
        dtQNoTbl.Load(rdr3);
        ds.Tables.Add(dtQNoTbl);

        rdr3.NextResult();

        // bind the second resultset
        DataTable dtOutMrkTbl = new DataTable("OutOfMarkTable");
        dtOutMrkTbl.Load(rdr3);
        ds.Tables.Add(dtOutMrkTbl);
        rdr3.Close();

        //**
        GridView1.DataSource = ds.Tables["OutOfMarkTable"];
        GridView1.DataBind(); //**
     }
}

Answer 1

The reason is your rdr3.NextResult() which advances the reader to the next result(if any). But that is already done in DataTable.Load. From MSDN:

The Load method consumes the first result set from the loaded
IDataReader, and after successful completion, sets the reader’s
position to the next result set, if any.

So you simply need to omit it. Another option is to use DatSet.Load(reader) instead to add the last two tables at once:

ds.Load(rdr, LoadOption.OverwriteChanges, "QstNoTable","OutOfMarkTable");
GridView1.DataSource = ds.Tables["OutOfMarkTable"]; 

DataSet.Load will not remove existing tables in the DataSet.