how to hide null cell before rotating GridView

Question

I want my GridView to hide the column which has null row value then rotate. I have some code below. But it is checking value after rotating. There is only one selected row and many columns.

 

protected void btnSearch_Click(object sender, EventArgs e)
    {
        gvDb.DataSource = (c());
        gvDb.DataBind();
        hideNull();
    }

    public DataSet c()
    {
        SqlConnection cn = new SqlConnection(cs);
        cn.Open();
        SqlDataAdapter ad = new SqlDataAdapter("select * from DESIGNSTABLE WHERE B210_APPL_NUMBER=" + txtID.Text + "", cn);
        DataSet ds = new DataSet();
        ad.Fill(ds, "DB");
        gvDb.DataSource = ds;
        gvDb.DataBind();
        cn.Close();
        return ds;
    }

    public DataSet FlipDataSet(DataSet my_DataSet)
    {
        DataSet ds = new DataSet();
        foreach (DataTable dt in my_DataSet.Tables)
        {
            DataTable table = new DataTable();
            for (int i = 0; i <= dt.Rows.Count; i++)
            {
                table.Columns.Add(Convert.ToString(i));
            }
            DataRow r = null;
            for (int k = 0; k < dt.Columns.Count; k++)
            {
                r = table.NewRow();
                r[0] = dt.Columns[k].ToString();
                for (int j = 1; j <= dt.Rows.Count; j++)
                    r[j] = dt.Rows[j - 1][k];
                table.Rows.Add(r);
            }
            ds.Tables.Add(table);
        }
        return ds;
    }
    protected void hideNull()
    {
        Boolean hasData = false;

        for (int col = 0; col < gvDb.HeaderRow.Cells.Count; col++)
        {
            for (int row = 0; row < gvDb.Rows.Count; row++)
            {
                if (!String.IsNullOrEmpty(gvDb.Rows[row].Cells[col].Text)
                    && !String.IsNullOrEmpty(HttpUtility.HtmlDecode(gvDb.Rows[row].Cells[col].Text).Trim()))
                {
                    hasData = true;
                    break;
                }
            }
            if (!hasData)
            {
                gvDb.HeaderRow.Cells[col].Visible = false;
                for (int hiddenrows = 0; hiddenrows < gvDb.Rows.Count; hiddenrows++)
                {
                    gvDb.Rows[hiddenrows].Cells[col].Visible = false;
                }
            }
            hasData = false;
        }
    }