Unable to create ListView programmatically

[Giovanni Pulvirenti]

Hello,

I'm really having too much troubles using RadListView. Now I'll try to briefly explain.

The project that I started to work on is a very specialized search engine using a complex data layer that can use one or more databases simultaneously. So I thought that was a good idea to use a RadListView with RadDataPager for a flexible paging.

Initially I was using the ASP.Net Controls version 2009.3.1103. Soon I realized that something was not going on as I expected: in fact, starting with no Data Source specified, after a postback initiated by another control, the data was not shown and the "no data template" was always presented. After a long search, finally I found a post in this forum that pointed me to this known bug.

Well, I did update the controls and the bug disappeared. But, unfortunately, now I'm stuck on the programmatic creation of the control. In fact I discovered that in design-time it is not possible to configure the RadListView via "smart tag option" since a valid data source is not specified.

A search engine cannot perform any query in a first page load, so I need to do all the data source job (dinamic query creation in response of the user parameter input) in a "if Page.IsPostBack then [...] End If" code block.

That's why I passed to the programmatic creation of the control.

Now, and this is the main problem to solve, it seems that there is no way to avoid this error message:

The RadListView control does not have an item placeholder specified.

For more clarity, this is the code-snippet in which I "try" to create the RadListView:

Private rlvResults As RadListView

Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init

        Me.BuildListView()


End Sub

Protected Sub BuildListView()

        Me.rlvResults = New RadListView()
        With Me.rlvResults
            .AllowCustomPaging = False
            .AllowCustomSorting = False
            .AlternatingItemTemplate = New GooWayTemplates.AlternatingItemTemplate()
            .EditItemTemplate = New GooWayTemplates.EditItemTemplate()
            .InsertItemTemplate = New GooWayTemplates.EditItemTemplate()
            .ItemTemplate = New GooWayTemplates.ItemTemplate()
            .EmptyDataTemplate = New GooWayTemplates.EmptyDataTemplate()
            .LayoutTemplate = New GooWayTemplates.LayoutTemplate()
            .SelectedItemTemplate = New GooWayTemplates.ItemTemplate()
            .ItemPlaceholderID = "itemPlaceholder"
            AddHandler .NeedDataSource, AddressOf rlvResults_NeedDataSource
            .AllowPaging = True
        End With

        Me.placeHListView.Controls.Add(Me.rlvResults)

 End Sub

Where am I wrong?

This is a fundamental step in a big project and I'm really confused :-)

Thanks in advance.

[Rosen]

Hello Giovanni,

The error you are getting does means that you should declare a control in your LayoutTemplate which to determine where the items (ItemTemplate, EditItemTemplate etc.) should be instantiated. Please refer to this live demo  for a sample of how to construct RadListView programmatically.

All the best,
Rosen
the Telerik team

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[Giovanni Pulvirenti]

Rosen,

Thank you very much,  this was very helpful.

Just a another point: my error was to use a "LiteralControl" as a "DIV tag builder" in this way:

   Public Class LayoutTemplate
        Implements ITemplate

        Public Sub New()
        End Sub

        Public Sub InstantiateIn(ByVal container As System.Web.UI.Control) Implements System.Web.UI.ITemplate.InstantiateIn

          Dim div As New LiteralControl("<div id=""itemPlaceholder""></div>")
          container.Controls.Add(div)

        End Sub
    End Class

Now, I think that LiteralControl class creates a span tag as container.

I changed the code in this way and all seems to be OK:

 Public Sub InstantiateIn(ByVal container As System.Web.UI.Control) Implements System.Web.UI.ITemplate.InstantiateIn

    Dim myDiv As New HtmlGenericControl("DIV")
    With myDiv
       .ID = "itemPlaceholder"
       .InnerText = "myLayoutTemplate"
    End With

    container.Controls.Add(myDiv)

 End Sub

Hope this can be useful for some other.

Best regards,

Giovanni Pulvirenti