Set gridview index when paging is true and page size is variable

when click the link of gridview at that time write this code before read the grid view


            int index = ((GridViewRow)((LinkButton)sender).Parent.Parent).DataItemIndex;
            if (index > (pagesize-1))
            {
                index = index - varaiblepageindex* pagesize;
              variable = Gridview.Rows[index].Cells[0].Text;

            }

And at gridview page indexchanging event write this code

{
      gridview.PageIndex = e.NewPageIndex;
            varaiblepageindex= gridview.PageIndex;
       gridview.databind();


}