Disappearing GridView - Newsgroup???

Discussion in 'ASP .Net' started by Don Miller, Apr 16, 2007.

  1. Don Miller

    Don Miller Guest

    This is a repost of a reproducible problem/bug with GridView with dynamic
    SQL and binding. Is there a better ASP.NET newsgroup I should post to where
    MS techs or MVPs take an interest in such problems?

    Thanks.


    Here is an example of what I believe is a bug in ASP.NET 2.0 GridView paging
    without postbacks (or at least not documented how to fix it). Once the
    GridView is displayed, clicking on any of the paging tools causes the
    GridView to completely disappear! This happens when either DataSets or
    DataTables are used (it doesn't work at all for DataReaders because they
    don't support paging apparently).

    If you remove the EnableSortingAndPageCallbacks parameter from the script
    below and add a PageIndexChanging sub, the paging works fine except there is
    a postback for every page. I would prefer to NOT have a postback and instead
    use the the AJAX-like callbacks when EnableSortingAndPageCallbacks is
    enabled.
    Protected Sub AuthorsGridView_PageIndexChanging(ByVal sender As Object,
    ByVal e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles
    AuthorsGridView.PageIndexChanging

    AuthorsGridView.PageIndex = e.NewPageIndex

    bindDataToGridView()

    End Sub

    So, how can you use GridView with callback paging without postbacks? What's
    missing from the code and why shouldn't the code work? And where is the
    documentation for avoiding this problem?

    Thanks for any help.

    <%@ Page language="VB" %>

    <script runat="server">

    Private Sub bindDataToGridView()
    'This example uses Microsoft SQL Server and connects
    Dim strSQL As String = "SELECT [au_fname], [au_lname], [city] FROM
    [authors]"
    Dim con As New
    System.Data.SqlClient.SqlConnection("server=localhost;database=pubs;integrated
    security=SSPI")
    Dim cmd = New System.Data.SqlClient.SqlCommand(strSQL, con)
    Dim ad As New System.Data.SqlClient.SqlDataAdapter(cmd)

    Dim ds As New Data.DataSet
    'Dim dt As New Data.DataTable

    ad.Fill(ds)
    'ad.Fill(dt)

    AuthorsGridView.DataSource = ds
    'AuthorsGridView.DataSource = dt
    AuthorsGridView.DataBind()
    End Sub

    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not IsPostBack Then
    bindDataToGridView()
    End If
    End Sub

    </script>

    <html>
    <body>
    <form id="Form1" runat="server">

    <h3>Disappearing GridView Example</h3>

    <asp:gridview id="AuthorsGridView"
    autogeneratecolumns="False"
    AllowPaging="True"
    EnableSortingAndPagingCallbacks="True"
    PageSize="3"
    runat="server" CellPadding="4" ForeColor="#333333" GridLines="None">
    <Columns>
    <asp:BoundField DataField="au_fname" HeaderText="First Name">
    </asp:BoundField>
    <asp:BoundField DataField="au_lname" HeaderText="Last Name">
    </asp:BoundField>
    <asp:BoundField DataField="City" HeaderText="City">
    </asp:BoundField>
    </Columns>
    <RowStyle BackColor="#E3EAEB" />
    <PagerStyle BackColor="#666666" ForeColor="White"
    HorizontalAlign="Center" />
    <HeaderStyle BackColor="#1C5E55" Font-Bold="True"
    ForeColor="White" />
    <AlternatingRowStyle BackColor="White" />
    </asp:gridview>
    </form>
    </body>
    </html>
     
    Don Miller, Apr 16, 2007
    #1
    1. Advertising

  2. Don Miller

    marss Guest

    Don Miller wrote:
    > So, how can you use GridView with callback paging without postbacks? What's
    > missing from the code and why shouldn't the code work? And where is the
    > documentation for avoiding this problem?


    Hi,
    The GridView disappers because it is empty. If you want to use a
    callback to change the page set GridView's datasource in the page load
    event handler. You don't need to process PageIndexChanging event, it
    is not raised.

    <asp:GridView ID="AuthorsGridView" runat="server" AllowPaging="True"
    EnableSortingAndPagingCallbacks="True" PageSize="3">
    ......
    </asp:GridView>

    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not IsPostBack Then
    bindDataToGridView()
    End If

    If Not IsCallback Then
    ......
    AuthorsGridView.DataSource = ds
    'AuthorsGridView.DataBind() Don't bind here!
    End If
    End Sub

    Regards
     
    marss, Apr 16, 2007
    #2
    1. Advertising

  3. Don Miller

    Don Miller Guest

    Thanks very much for the reply. What I'm really trying to do is to
    dynamically change the GridView by changing (on command) the SELECT
    statement for the GridView. Initially, the GridView is empty until a command
    is chosen (with a hyperlink button). In the actual application the GridView
    is only one of several on a page that are hidden by changing Views. I would
    like to do this (AJAX paging) with a SQL datasource by dynamically changing
    the SELECT statement but I run into the same disappearing GridView when I
    tried that (see example below)

    I appreciate your help and I obviously don't understand how these things
    work but I've already spent hours of reading and trial and error and seem no
    closer. Thanks again.

    <%@ Page language="VB" %>

    <script runat="server">

    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    End Sub

    Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As
    System.EventArgs)
    GridViewSQLDataSource.SelectCommand = "SELECT [au_fname],
    [au_lname], [city] FROM [authors] WHERE [city] = 'Oakland'"
    End Sub

    Protected Sub LinkButton2_Click(ByVal sender As Object, ByVal e As
    System.EventArgs)
    GridViewSQLDataSource.SelectCommand = "SELECT [au_fname],
    [au_lname], [city] FROM [authors]"
    End Sub
    </script>

    <html>
    <body>
    <form id="Form1" runat="server">

    <h3>Disappearing GridViews</h3>

    <asp:LinkButton ID="LinkButton1" runat="server"
    OnClick="LinkButton1_Click">Oakland Only</asp:LinkButton>
    <asp:LinkButton ID="LinkButton2" runat="server"
    OnClick="LinkButton2_Click">All Cities</asp:LinkButton>

    <asp:gridview id="AuthorsGridView"
    autogeneratecolumns="False"
    AllowPaging="True"
    EnableSortingAndPagingCallbacks="True"
    PageSize="3"
    DataSourceID = "GridViewSQLDataSource"
    runat="server" CellPadding="4" ForeColor="#333333" GridLines="None">
    <Columns>
    <asp:BoundField DataField="au_fname" HeaderText="First Name">
    </asp:BoundField>
    <asp:BoundField DataField="au_lname" HeaderText="Last Name">
    </asp:BoundField>
    <asp:BoundField DataField="City" HeaderText="City">
    </asp:BoundField>
    </Columns>
    <RowStyle BackColor="#E3EAEB" />
    <PagerStyle BackColor="#666666" ForeColor="White"
    HorizontalAlign="Center" />
    <HeaderStyle BackColor="#1C5E55" Font-Bold="True"
    ForeColor="White" />
    <AlternatingRowStyle BackColor="White" />
    </asp:gridview>

    <asp:SqlDataSource ID="GridViewSQLDataSource"
    ConnectionString="server=localhost;database=pubs;integrated
    security=SSPI"
    runat="server">
    </asp:SqlDataSource>

    </form>
    </body>
    </html>
     
    Don Miller, Apr 16, 2007
    #3
  4. Don Miller

    marss Guest

    Don Miller wrote:
    > Thanks very much for the reply. What I'm really trying to do is to
    > dynamically change the GridView by changing (on command) the SELECT
    > statement for the GridView. Initially, the GridView is empty until a command
    > is chosen (with a hyperlink button). In the actual application the GridView
    > is only one of several on a page that are hidden by changing Views. I would
    > like to do this (AJAX paging) with a SQL datasource by dynamically changing
    > the SELECT statement but I run into the same disappearing GridView when I
    > tried that (see example below)



    Save the chosen select command text in the ViewState and assign it to
    GridViewSQLDataSource.SelectCommand in the page load event handler.
    Example:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As
    System.EventArgs) Handles Me.Load
    If (IsCallback) Then
    GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    End If
    End Sub

    Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As
    System.EventArgs)
    Me.SelectCommand = "SELECT .... "
    GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    End Sub

    Protected Sub LinkButton2_Click(ByVal sender As Object, ByVal e As
    System.EventArgs)
    Me.SelectCommand = "SELECT ...."
    GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    End Sub

    Private Property SelectCommand() As String
    Get
    Return ViewState("SelectCommand").ToString()
    End Get
    Set(ByVal value As String)
    ViewState("SelectCommand") = value
    End Set
    End Property

    Regards
     
    marss, Apr 17, 2007
    #4
  5. Don Miller

    Don Miller Guest

    Thank you so much! I'm still learning and quite sure I wouldn't have come up
    that solution using ViewState or even know where to place the code in the
    Event cascade (onLoad, onCallback, GridView init/load, etc.).

    It still seems like a bug to me that the SELECT command for the DataSource
    has to be reset again with a Callback. It is set for the GridView each time
    a link button was pressed and it seems like that should be enough. Why
    should a dynamic SELECT statement assigned to a DataSource get trashed on a
    Callback? This solution (thanks again) seems like a hack to get around this
    unexpected behavior. I mean, why should anyone expect that you have to do
    this?

    Anyway, I did find I had to add one line of code to reset the PageIndex back
    to 0 when a new SELECT is displayed to keep the Pages straight.

    Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As
    System.EventArgs)
    Me.SelectCommand = "SELECT [au_fname], [au_lname], [city] FROM
    [authors] WHERE [city] = 'Oakland'"
    GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    AuthorsGridView.PageIndex = 0
    End Sub

    "marss" <> wrote in message
    news:...
    >
    > Don Miller wrote:
    >> Thanks very much for the reply. What I'm really trying to do is to
    >> dynamically change the GridView by changing (on command) the SELECT
    >> statement for the GridView. Initially, the GridView is empty until a
    >> command
    >> is chosen (with a hyperlink button). In the actual application the
    >> GridView
    >> is only one of several on a page that are hidden by changing Views. I
    >> would
    >> like to do this (AJAX paging) with a SQL datasource by dynamically
    >> changing
    >> the SELECT statement but I run into the same disappearing GridView when I
    >> tried that (see example below)

    >
    >
    > Save the chosen select command text in the ViewState and assign it to
    > GridViewSQLDataSource.SelectCommand in the page load event handler.
    > Example:
    >
    > Protected Sub Page_Load(ByVal sender As Object, ByVal e As
    > System.EventArgs) Handles Me.Load
    > If (IsCallback) Then
    > GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    > End If
    > End Sub
    >
    > Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As
    > System.EventArgs)
    > Me.SelectCommand = "SELECT .... "
    > GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    > End Sub
    >
    > Protected Sub LinkButton2_Click(ByVal sender As Object, ByVal e As
    > System.EventArgs)
    > Me.SelectCommand = "SELECT ...."
    > GridViewSQLDataSource.SelectCommand = Me.SelectCommand
    > End Sub
    >
    > Private Property SelectCommand() As String
    > Get
    > Return ViewState("SelectCommand").ToString()
    > End Get
    > Set(ByVal value As String)
    > ViewState("SelectCommand") = value
    > End Set
    > End Property
    >
    > Regards
    >
     
    Don Miller, Apr 17, 2007
    #5
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. =?Utf-8?B?dmFuZGls?=
    Replies:
    2
    Views:
    1,192
    Eliyahu Goldin
    Jan 25, 2007
  2. Don Miller

    Disappearing GridView Paging BUG!

    Don Miller, Apr 13, 2007, in forum: ASP .Net
    Replies:
    0
    Views:
    618
    Don Miller
    Apr 13, 2007
  3. =?Utf-8?B?Sm9yaXMgWndhZW5lcG9lbA==?=

    disappearing controls from gridview templatecolumn

    =?Utf-8?B?Sm9yaXMgWndhZW5lcG9lbA==?=, Sep 7, 2007, in forum: ASP .Net
    Replies:
    1
    Views:
    1,107
    =?Utf-8?B?S2V2aW4gQi4=?=
    Sep 17, 2007
  4. steve.falzon@

    Gridview - disappearing data when column is hidden

    steve.falzon@, Sep 20, 2006, in forum: ASP .Net Web Controls
    Replies:
    0
    Views:
    177
    steve.falzon@
    Sep 20, 2006
  5. Vinki

    disappearing gridlines in gridview

    Vinki, Apr 26, 2007, in forum: ASP .Net Web Controls
    Replies:
    1
    Views:
    262
    KyleK
    May 17, 2007
Loading...

Share This Page