sorting and paging with gridview asp net

Question

I m trying to get a gridview to sort and page manually with no success   The problem is that when a user clicks the column they want to sort  it sorts that page  but doesn t sort the datasource  dataview  behind the gridview   So when they progress to a different page  their sort is lost   Pretty much I m looking for a sort that will actually sort the datasource behind the gridview   Here is what I have so far   protected void GridView OnSort object sender  GridViewSortEventArgs e                String sortExpression   e SortExpression           if  GridViewSortDirection    SortDirection Ascending                        DataView myDataView   new DataView mybll GetItemsOrdered                 myDataView Sort   sortExpression     DESC               GridView DataSource   myDataView              GridView DataBind                      else                       DataView myDataView   new DataView mybll GetItemsOrdered                 myDataView Sort   sortExpression     ASC               GridView DataSource   myDataView              GridView DataBind                      Any help would be appreciated   Thanks

User · Answer

lt asp GridView      ID  GridView1  runat  server  AutoGenerateColumns  false  AllowSorting  True  onsorting  GridView1 Sorting  EnableViewState  true  gt        lt Columns gt           lt asp BoundField DataField  bookid  HeaderText  BOOK ID SortExpression  bookid     gt           lt asp BoundField DataField  bookname  HeaderText  BOOK NAME    gt           lt asp BoundField DataField  writer  HeaderText  WRITER    gt           lt asp BoundField DataField  totalbook  HeaderText  TOTALBOOK  SortExpression  totalbook     gt           lt asp BoundField DataField  availablebook  HeaderText  AVAILABLE BOOK    gt       lt  Columns gt   lt  asp GridView gt    Code behind      protected void Page Load object sender  EventArgs e            if   IsPostBack                string query    SELECT   FROM book               DataTable DT   new DataTable                SqlDataAdapter DA   new SqlDataAdapter query  sqlCon               DA Fill DT                GridView1 DataSource   DT              GridView1 DataBind                         protected void GridView1 Sorting object sender  GridViewSortEventArgs e             string query    SELECT   FROM book           DataTable DT   new DataTable            SqlDataAdapter DA   new SqlDataAdapter query  sqlCon           DA Fill DT            GridView1 DataSource   DT          GridView1 DataBind             if  DT    null                DataView dataView   new DataView DT               dataView Sort   e SortExpression         ConvertSortDirectionToSql e SortDirection                GridView1 DataSource   dataView              GridView1 DataBind                         private string GridViewSortDirection           get   return ViewState  SortDirection   as string     DESC             set   ViewState  SortDirection     value               private string ConvertSortDirectionToSql SortDirection sortDirection            switch  GridViewSortDirection                case  ASC                   GridViewSortDirection    DESC                   break               case  DESC                   GridViewSortDirection    ASC                   break                     return GridViewSortDirection

User · Answer

Save your sorting order in a ViewState   private const string ASCENDING     ASC   private const string DESCENDING     DESC    public SortDirection GridViewSortDirection       get               if  ViewState  sortDirection      null              ViewState  sortDirection     SortDirection Ascending           return  SortDirection  ViewState  sortDirection                              set   ViewState  sortDirection     value        protected void GridView Sorting object sender  GridViewSortEventArgs e        string sortExpression   e SortExpression       if  GridViewSortDirection    SortDirection Ascending                GridViewSortDirection   SortDirection Descending          SortGridView sortExpression  DESCENDING             else               GridViewSortDirection   SortDirection Ascending          SortGridView sortExpression  ASCENDING                 private void SortGridView string sortExpression string direction            You can cache the DataTable for improving performance     DataTable dt   GetData   Tables 0         DataView dv   new DataView dt        dv Sort   sortExpression   direction                GridView1 DataSource   dv      GridView1 DataBind                 Why you don t want to use existing sorting functionality  You can always customize it   Sorting Data in a GridView Web Server Control at MSDN  Here is an example with customization    http   www netomatix com development GridViewSorting aspx

User · Answer

More simple way          Dim dt As DataTable   DirectCast GridView1 DataSource  DataTable      Dim dv As New DataView dt       If GridView1 Attributes  dir     SortDirection Ascending Then         dv Sort   e SortExpression  amp    DESC           GridView1 Attributes  dir     SortDirection Descending      Else         GridView1 Attributes  dir     SortDirection Ascending         dv Sort   e SortExpression  amp    ASC       End If      GridView1 DataSource   dv     GridView1 DataBind

User · Answer

Tarkus s answer works well   However  I would suggest replacing VIEWSTATE with SESSION     The current page s VIEWSTATE only works while the current page posts back to itself and is gone once the user is redirected away to another page   SESSION persists the sort order on more than just the current page s post-back   It persists it across the entire duration of the session   This means that the user can surf around to other pages  and when he comes back to the given page  the sort order he last used still remains   This is usually more convenient     There are other methods  too  such as persisting user profiles   I recommend this article for a very good explanation of ViewState and how it works with a web page s life cycle   https   msdn microsoft com en-us library ms972976 aspx  To understand the difference between VIEWSTATE  SESSION and other ways of persisting variables  I recommend this article   https   msdn microsoft com en-us library 75x4ha6s aspx

User · Answer

I found a much easier way  which allows you to still use the built in sorting paging of the standard gridview     create 2 labels   set them to be visible   false   I called mine lblSort1 and lblSortDirection1  then code 2 simple events    the page sorting  which writes to the text of the invisible labels  and the page index changing  which uses them     Private Sub gridview Sorting sender As Object  e As GridViewSortEventArgs  Handles gridview Sorting lblSort1 Text   e SortExpression lblSortDirection1 Text   e SortDirection End Sub  Private Sub gridview PageIndexChanging sender As Object  e As GridViewPageEventArgs  Handles gridview PageIndexChanging     gridview Sort lblSort1 Text  CInt lblSortDirection1 Text   End Sub   this is a little sloppier than using global variables  but I ve found with asp especially that global vars are  well  unreliable

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