just copy and paste the below code all your grid data will be in datatable dt.
if (rbw.Checked == true)
{
Sql = "select Category,Questions,Answers from Tb_Staff_Doubt_Register Where Questions like '%" + Txtsearch.Text + "%' or Answers like '%" + Txtsearch.Text + "%' ";
Dr = SCon.ReadSql(Sql);
GridView1.DataSource = Dr;
GridView1.DataBind();
GridView1.Visible = true;
DataTable dt=GridVeiw1.DataSource as DataTable;
}