Deleting column causes column does not exist in table error

I'm populating a DataSet from an Sql query. I fetch some extra columns in my query as i need them to for further queries. I delete those columns after im' done with them, but i get a Column "columnname" doesn't exist in "dataset" error when i try to bind the DataSet to a GridView.

Any ideas what could be the cause?

Edit: here's the code The actual error message: "Column 'BID' does not belong to table results."

String command = "SELECT B.BID, B.NAME 'Name', B.FARE 'Fare', B.DEPARTURE 'Departure', B.MAX_SEATS 'MAX', NULL 'Seats Available' "+
                 "FROM ROUTE R, BUS B "+
                 "WHERE R.FROM_LOCATION = @from AND R.TO_LOCATION = @to ";
if(_ac) command += "AND B.AC = @ac ";
if(_volvo) command += "AND B.VOLVO = @volvo ";
if(_sleeper) command += "AND B.SLEEPER = @sleeper ";
command += "AND B.RUNS_ON LIKE '%"+day+"%' AND R.RID = B.RID";
SqlCommand cmd = new SqlCommand(command, con);

cmd.Parameters.AddWithValue("@from", fromValue);
cmd.Parameters.AddWithValue("@to", destValue);
if(_ac) cmd.Parameters.AddWithValue("@ac", _ac);
if(_volvo) cmd.Parameters.AddWithValue("@volvo", _volvo);
if(_sleeper) cmd.Parameters.AddWithValue("@sleeper", _sleeper);

SqlDataAdapter adapter = new SqlDataAdapter(cmd);
_results = new DataSet();

con.Open();
adapter.Fill(_results, "results");

DataTable dt = _results.Tables["results"];
if(dt.Rows.Count > 0 ) {
    for(int i = 0; i < dt.Rows.Count; i++) {
        DataRow row = dt.Rows[i];
        int max = Int32.Parse(row["MAX"].ToString());
        String bid = row["BID"].ToString();
        cmd.CommandText = "SELECT B.MAX_SEATS-SUM(RS.SEATS_BOOKED) 'REMAIN', RS.BID "+
                          "FROM RESERVATION RS, BUS B "+
                          "WHERE RS.DATE_JOURNEY = @date AND RS.BID = @bid AND B.BID = RS.BID "+
                          "GROUP BY B.MAX_SEATS, RS.BID";
        cmd.Parameters.AddWithValue("@date", dateValue);
        cmd.Parameters.AddWithValue("@bid", bid);

        SqlDataReader reader = cmd.ExecuteReader();
        if(reader.Read()) {
            max = Int32.Parse(reader["REMAIN"].ToString());
        }

        // If all seats are booked, remove the row from the table.
        if(max == 0) { dt.Rows.Remove(row); }
        else {
            row["Seats Available"] = max;
        }

        reader.Close();
        cmd.Parameters.Clear();
        dt.AcceptChanges();
    }

    if(dt.Columns.CanRemove(dt.Columns["BID"]))
        dt.Columns.Remove("BID");
    if(dt.Columns.CanRemove(dt.Columns["MAX"]))
        dt.Columns.Remove("MAX");

    dt.AcceptChanges();
    _results.AcceptChanges();

    // Bind the results to a GridView
    GridView1.DataSource = _results;
    GridView1.DataBind();

    // Dispaly Results Panel
    results.Visible = true;
}
else {
    message.Text = "No bus found";
    message.Visible = true;
}

}

GridView1 Markup:

<asp:GridView ID="GridView1" runat="server" onrowcreated="GridView1_RowCreated" EnableViewState="False" GridLines="Horizont开发者_StackOverflow社区al">
    <Columns>
    <asp:TemplateField>
        <ItemTemplate>
            <asp:Literal ID="RadioButtonMarkup" runat="server"></asp:Literal>
        </ItemTemplate>
    </asp:TemplateField>
    </Columns>
</asp:GridView>

Database columns:

ROUTE: RID, FROM_LOCATION, TO_LOCATION

BUS: RID, BID, NAME, AC, VOLVO, SLEEPER, FARE, MAX_SEATS, RUNS_ON, DEPARTURE

RESERVATIONS: TID, PID, BID, SEATS_BOOKED, DATE_BOOKED, DATE_JOURNEY

EDIT: Just noticed, if i only remove column 'MAX', it works, i see the GridView without that column, but removing 'BID' somehow gives me that error.

EDIT: Solved! Was trying to access the BID column in the RowCreated method, which caused this. Thanks to all who helped.

I'd suggest adding the alias "BID" to B.BID in your first sql statement. Maybe that's what it's looking for.

Ok, I had written a very long reply but just deleted it. Are you sure you are binding the right datasource to your grid?

Maybe:

GridView1.DataSource = _results.Tables["results"];

or

GridView1.DataSource = dt;

would work.

If this is the markup of your grid, I would suggest that you modify the grid to specifically show the columns that you need.