RowDataBind Event not firing on postback

//for binding Grid
 protected void getdata()
    {
        try
        {
            DataTable dt = new DataTable();

            for (int i = 0; i < int.Parse(txtcolumns.Text); i++)
            {
                DataColumn dcol = new DataColumn();
                //dcol.AutoIncrement = true;
                dt.Columns.Add(dcol);

            }
            for (int i = 0; i < int.Parse(txtrows.Text); i++)
            {
                DataRow dr = dt.NewRow();
                dt.Rows.Add(dr);
            }
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }
        catch (Exception ex)
        {
            lblerror.Visible = true;
            lblerror.Text = ex.Message;
        }
    }

//Rowdatabound
 try
        {
            int inte = e.Row.RowIndex + 1;
            if (cbxseats.Checked == true)
            {
                if (inte == int.Parse(txtdivider.Text))
                {

                    if (e.Row.RowType == DataControlRowType.DataRow)
                    {
                        for (int i = 0; i < int.Parse(txtcolumns.Text); i++)
                        {
                            TextBox tbx = new TextBox();
                            tbx.Width = 40;
                            tbx.Height = 20;
                            tbx.ID = "txtbox" + inte + i;
                            //tbx.Text = "45";
                            //tbx.ReadOnly = true;
                            if (i + 1 == int.Parse(txtcolumns.Text))
                            {
                                e.Row.Cells[i].Controls.Add(tbx);
                            }
                        }
                    }
                }
                else
                {
                    for (int i = 0; i < int.Parse(txtcolumns.Text); i++)
                    {
                        if (e.Row.RowType == DataControlRowType.DataRow)
                        {
                            TextBox tbx = new TextBox();
                            tbx.Width = 40;
                            tbx.Height = 20;
                            tbx.ID = "txtbox" + inte + i;
                            e.Row.Cells[i].Controls.Add(tbx);
                        }
                    }
                }
            }
            else if (cbxbearths.Checked == true)
            {
                
                if (inte == int.Parse(txtdivider.Text))
                {

                    if (e.Row.RowType == DataControlRowType.DataRow)
                    {
                        e.Row.Cells[0].Controls.Add(new LiteralControl("<br/>"));
                       
                    }
                }
                else
                {
                    for (int i = 0; i < int.Parse(txtcolumns.Text); i++)
                    {
                        if (e.Row.RowType == DataControlRowType.DataRow)
                        {
                            TextBox tbx = new TextBox();
                            tbx.Width = 80;
                            tbx.Height = 20;
                            tbx.ID = "txtbox" + inte + i;
                            e.Row.Cells[i].Controls.Add(tbx);
                        }
                    }
                }

            }
catch (Exception ex)
      {
          lblerror.Visible = true;
          lblerror.Text = ex.Message;
      }
  }

//on button click event i am calling that getdata() to bind the gridview
protected void btnlayout_Click(object sender, EventArgs e)
   {
       try
       {
               getdata();
               lbllower.Visible = true;
               //btnupperdeck_Click(sender, e);
       }
       catch (Exception ex)
       {
           lblerror.Visible = true;
           lblerror.Text = ex.Message;
       }
   }