send Pivot column field and Row field to another page through button onGridview

Hi Team

I want to send column field and Row field of selected value of pivot result to another page through button. In Gridview I was able to get the selected values from button, but that values are not passing to another page till I again click on show button.

my code


    protected void Button2_Click(object sender, EventArgs e)
    {
        SqlConnection sqlConnection = new SqlConnection(strSQLconnection);
        SqlCommand sqlCommand = new SqlCommand("SELECT * FROM ( SELECT CUST, PRODUCT, cast(QTY as int)  as QTY FROM Product) up PIVOT (SUM(QTY) FOR PRODUCT IN (VEG, SODA, MILK, BEER, CHIPS)) AS pvt ORDER BY CUST", sqlConnection);
        sqlConnection.Open();

        SqlDataReader reader = sqlCommand.ExecuteReader();

        Gridview1.DataSource = reader;
        Gridview1.DataBind();
    }
    private List<string> _headers = new List<string>();
    protected void Gridview1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        //Collect the texts from the column headers
        if (e.Row.RowType == DataControlRowType.Header)
        {
            for (int i = 0; i <= e.Row.Cells.Count - 1; i++)
            {
                this._headers.Add(e.Row.Cells[i].Text);
            }
        }

        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            for (int i = 0; i <= e.Row.Cells.Count - 1; i++)
            {
                if (TryToParse(e.Row.Cells[i].Text) > 0)
                {
                    string rowKey = e.Row.Cells[0].Text;
                    string column = this._headers[i];

                    Button link = new Button();
                    link.BackColor=Color.White;
                    link.BorderStyle = BorderStyle.None;
                    link.Text = e.Row.Cells[i].Text;
                    link.PostBackUrl = "Default.aspx?key=" + rowKey + "&column=" + column;
                    e.Row.Cells[i].Controls.Clear();
                    e.Row.Cells[i].Controls.Add(link);
                    string Name = Request.QueryString["key"];
                    string Column = Request.QueryString["column"];
                    if (Name != null && Column != null)
                    {   
                        Page.ClientScript.RegisterStartupScript(GetType(), "", "window.open('Default2.aspx?key=" + Name + "&column=" + Column + "','','width=500,height=300');", true);
                    }
                }
            }
        }
    }
    private int TryToParse(string value)
    {
        int number;
        bool result = Int32.TryParse(value, out number);
        if (result)
            return number;
        else
            return 0;
    }

    
}