Here is an example to put a drop down list in a gridview to control its pagesize

 Protected Sub gvProjectList_RowCreated(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles gvProjectList.RowCreated

        If e.Row.RowType = DataControlRowType.Pager Then

            Dim ddl As New DropDownList

            Dim li As ListItem

  [...]