Re: Custom Datagrid disappearing on Postback
- From: "Jeff" <jeffmagill@xxxxxxxxx>
- Date: 4 Dec 2006 13:57:54 -0800
viewstate. to do so, you need to override the LoadViewState andFrom that code, it doesnt look like you are saving the data in the
SaveViewState subroutines.
I was going to try to give you a relevant code snippet but I think that
might be more confusing than anything else. If this is what youre
dealing with, you might want to try googling around for a tutorial to
overload these functions. I cant seem to find the one I learned from.
Protected Overrides Sub LoadViewState(ByVal savedState As Object)
If Not savedState Is Nothing Then
MyBase.LoadViewState(savedState)
End If
End Sub
Protected Overrides Function SaveViewState() As Object
Dim baseState As Object = MyBase.SaveViewState()
If baseState Is Nothing Then
Return Nothing
End If
Return baseState
End Function
GJH wrote:
Thanks again Jeff,
Thats what I ended up doing was saving to the viewstate. my only thing is,
its not acting like a standard datagrid like Microsoft's does. usually I
just create a function that fills the dataset and binds the grid and I dont
have to keep calling the bindgrid() part ever page load.
In my dgTest.vb file, am I missing code? Do I need to enable the ViewState
here to keep the grid visible?
Imports System.ComponentModel
Imports System.Web.UI
<DefaultProperty("Text"), ToolboxData("<{0}:dgTest
runat=server></{0}:dgTest>")> Public Class dgTest
Inherits System.Web.UI.WebControls.DataGrid
Dim _text As String
<Bindable(True), Category("Appearance"), DefaultValue("")> Property [Text]()
As String
Get
Return _text
End Get
Set(ByVal Value As String)
_text = Value
End Set
End Property
Protected Overrides Sub Render(ByVal output As System.Web.UI.HtmlTextWriter)
Me.EnsureChildControls()
MyBase.Render(output)
End Sub
Protected Overrides Sub OnInit(ByVal e As System.EventArgs)
Me.EnsureChildControls()
End Sub
"Jeff" <jeffmagill@xxxxxxxxx> wrote in message
news:1165257537.439934.211560@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
You can save the data into the ViewState object. Basically, the
viewstate is an object that holds all the information for each of the
controls on the page across postbacks. Then on postback, instead of
loading from the database, you load from the ViewState.
Not being familiar with your application, I cant say exactly what would
be the best way to accomplish this. Off the top of my head, you might
want to try to load the database information into a DataTable, bind the
DataGrid to the Table, then save the DataTable into the viewstate. On
postback, load from the DataTable.
GJH wrote:
Thanks Jeff,
if I remove the "IF" in the page load statement then yes it works, but
then
I am hitting the database on every postback.
With the MS datagrdd I can just fill the dataset/bind the grid on the
initial page load in the IF Not IsPostBack statement
What is my datagrid missing thats different from MS standard datagrid?
thanks,
Greg
"Jeff" <jeffmagill@xxxxxxxxx> wrote in message
news:1165256222.602754.189870@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
My guess would be that since youre populating your datagrid in the code
behind, that the data is not being saved in the viewstate.
What happens when you take the if statement out of the Page.Load
handler and just call BindList every time the page loads?
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
BindList()
End Sub
GJH wrote:
I have a Web Custom Control datagrid written in VB.NET and when the
page
does a postback from a Selected Index or Sort command the datagrid
disappears??? anyone know why?
thanks
here is the control's code:
Imports System.ComponentModel
Imports System.Web.UI
<DefaultProperty("Text"), ToolboxData("<{0}:dgTest
runat=server></{0}:dgTest>")> Public Class dgTest
Inherits System.Web.UI.WebControls.DataGrid
Dim _text As String
<Bindable(True), Category("Appearance"), DefaultValue("")> Property
[Text]()
As String
Get
Return _text
End Get
Set(ByVal Value As String)
_text = Value
End Set
End Property
Protected Overrides Sub Render(ByVal output As
System.Web.UI.HtmlTextWriter)
Me.EnsureChildControls()
MyBase.Render(output)
End Sub
Protected Overrides Sub OnInit(ByVal e As System.EventArgs)
Me.EnsureChildControls()
End Sub
End Class
Here is my webpage
Dim mySort As String
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
If Not Page.IsPostBack Then
BindList()
End If
End Sub
Private Sub BindList(Optional ByVal sort As String = "")
Dim query As String = "select * from employees"
Dim da As New SqlDataAdapter(query, cnn)
Dim ds As New DataSet
Try
da.Fill(ds, "employees")
ds.Tables(0).DefaultView.Sort = sort
DgTest1.DataSource = ds
DgTest1.DataMember = "employees"
DgTest1.DataBind()
Catch ex As Exception
Response.Write(ex.Message)
End Try
End Sub
Private Sub GJHAddToCartDataGrid1_SortCommand(ByVal source As Object,
ByVal
e As System.Web.UI.WebControls.DataGridSortCommandEventArgs) Handles
GJHAddToCartDataGrid1.SortCommand
mySort = e.SortExpression & " ASC"
BindList(mySort)
End Sub
Private Sub DgTest1_SelectedIndexChanged(ByVal sender As
System.Object,
ByVal e As System.EventArgs) Handles DgTest1.SelectedIndexChanged
Response.Write("hi")
End Sub
.
- References:
- Custom Datagrid disappearing on Postback
- From: GJH
- Re: Custom Datagrid disappearing on Postback
- From: Jeff
- Re: Custom Datagrid disappearing on Postback
- From: GJH
- Re: Custom Datagrid disappearing on Postback
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