how to use update gridview data without using database in c#

First make a Data Table for your data. Then assign it to your Gridview . When ever you perform operation on Gridview assign gridview data to datatable and you can use it again.

DataTable dt = new DataTable();
        DataRow dr;
        dt.Columns.Add(new System.Data.DataColumn("BookName", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("BookQty", typeof(String)));
        dt.Columns.Add(new System.Data.DataColumn("BookImg", typeof(String)));
    foreach (GridViewRow row in gvShoppingCart.Rows)
        {
            Image Bookimg = (Image)row.FindControl("BookImg");
            Label Booknames = (Label)row.FindControl("lblBookName");
            TextBox Bookqty = (TextBox)row.FindControl("TXTQty");
            Label TotalPrice = (Label)row.FindControl("LBLTotal");
            dr = dt.NewRow();
            dr[0] = Booknames.Text;
            dr[1] = Bookqty.Text;
            dr[2] = Bookimg.ImageUrl.ToString();
            dt.Rows.Add(dr);
        }

        Session["QtyTable"] = dt;