Hello,

Based On my investigation, this is not cause by PlaceHolder. Event a small div can also replicate your issue. Some of your approaches is not correct and not postback condition in Page_Load also cause this issue. 

Please see my approaches in below. Hope this helps.

Imports System
Imports System.Data
Imports System.Configuration
Imports System.Collections
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls
Imports ISNet.WebUI.WebCombo
Public Class webCombo
    Inherits System.Web.UI.Page    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        PlaceHolder1.Controls.Add(createCBO)
    End Sub
    Private Function GetData2() As DataTable
        Dim dt As New DataTable
        With dt.Columns
            .Add("Text")
            .Add("Value")
            .Add("Display")
        End With
        For i As Integer = 1 To 250
            With dt.Rows
                .Add(i & i, i, i)
            End With
        Next
        Return dt
    End Function
    Private Function createCBO() As WebCombo
        Dim cboWebCombo As New WebCombo
        Dim dt As New DataTable
        Dim sbBindText As New System.Text.StringBuilder
        AddHandler cboWebCombo.InitializeDataSource, AddressOf cboWebCombo_InitializeDataSource
        With cboWebCombo
            .ID = "cbo"
            .UseDefaultStyle = True
            .Enabled = True
            .Latency = 250
            .AllowAutoPostback = False
        End With
        Return cboWebCombo
    End Function
    Protected Sub cboWebCombo_InitializeDataSource(ByVal sender As Object, ByVal e As ISNet.WebUI.WebCombo.DataSourceEventArgs)
        Dim cboWebCombo As WebCombo = CType(sender, WebCombo)
        e.DataSource = GetData2()
        cboWebCombo.DataValueField = "Text"
        cboWebCombo.DataTextField = "Value"
    End Sub
End Class

Regards,
Handy

Hello,

  Thanks Handy for providing a better approach. I have tried the suggestion. But the problem still persist, please kindly help.

Thanks again,

Fung

Hello,

Which one is not working? The fullpostback should be not persisted anymore. Please see my attached sample.

Regards,
Handy

Hello,

  Thanks, your sample is working. Since I need to generate a lot of webcom in one page and it increase the page's loading time if I go through the whole page load each time flypostback.

to describe in code would be:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then
            PlaceHolder1.Controls.Add(createCBO)
        End If

    End Sub

but when I do this to the sample you provided, the webcombo would not be able to retreive data. Is there any work around for this case?

Thanks and Regards,

Fung

Hello Fung,

I did not understand about "it won't be able to retieve data". Shouldn't when you type in WebCombo pr show the dropdown, it will trigger IntializeDataSource event?

Unfortunately, you could not place Not IsPostBack condition, because WebCombo must be always created. Otherwise, it's gone.

Regards,
Handy