How to store Gridview data into Datatable

string str = "select pcode,fyyear,date,salary,ta,contigency,nrc,institcharges,others from monthly";
        SqlDataAdapter adp = new SqlDataAdapter(str, con);
        DataTable dt = new DataTable();
        adp.Fill(dt);
        GridView1.DataSource = dt;
        GridView1.DataBind();