Finally i got the solution
i have used paging to solve the problem
AllowPaging="true" PageSize="5000"
in gridview.
in vb.net add the below code.
Private Sub grdSearch_PageIndexChanging(sender As Object, e As GridViewPageEventArgs) Handles grdSearch.PageIndexChanging
grdSearch.PageIndex = e.NewPageIndex
Bindgrid()
End Sub