Add a template field to your grid put a checkbox in that template field for selection purpose.
HtmlTable tbl=new HtmlTable();
foreach(GridViewRow row in GridView1.Rows)
{
if(row.RowType==RowType.DataRow)
{
CheckBox chk =row.FindControl("chk") as CheckBox;
if(chk.Checked)
{
HtmlTableRow r=new HtmlTableRow();
HtmlTableCell c1=new HtmlTableCell();
HtmlTableCell c2=new HtmlTableCell();
c1.InnerHtml=((Label)row.FindControl("Label1")).Text;
c2.InnerHtml=((Label)row.FindControl("Label2")).Text;
r.Cells.Add(c1);
r.Cells.Add(c2);
tbl.Rows.Add(r);
}
}
}
HtmlTextWriter htw=new HtmlTextWriter();
stringWriter sw=new stringWriter(htw);
tbl.RenderControl(sw);