Can't move last item in RadListBox

[DGraham]

Hi,

The items transfer fine between the two list boxes unless its the last item in the list box, where I get the following error:

Error occurs on first line of RadListBoxContacts_Transferred (VB code)
e.SourceListBox.SelectedItem.DataKey

Error:
'Object reference not set to an instance of an object.'

 please see code below:

ASPX

<telerik:RadListBox ID="RadListBoxContacts" runat="server" Skin="Telerik" AutoPostBack="true"
                                                                AutoPostBackOnTransfer="true" DataKeyField="contactID" DataTextField="Description"
                                                                Width="240px" Height="200px" AllowTransfer="true" TransferToID="RadListBoxServiceContacts"
                                                                ButtonSettings-ShowTransferAll="false" EnableViewState ="true">
                                                                <ButtonSettings ShowTransferAll="False" />
                                                            </telerik:RadListBox>


<telerik:RadListBox ID="RadListBoxServiceContacts" runat="server" Skin="Telerik"
                                                                DataKeyField="contactID" DataTextField="Description" Width="245px" Height="200px"
                                                                AutoPostBack="True" EnableViewState ="true" >
                                                            </telerik:RadListBox>

VB

Private Sub RadListBoxServiceContacts_Deleted(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadListBoxEventArgs) Handles RadListBoxServiceContacts.Deleted
        Session("Avalability") = "Delete"
        Me.lblServiceContactDescription.Text = "Select a contact to view details"
        Me.lblServiceContactDetails.Text = ""
    End Sub
    Private Sub RadListBoxServiceContacts_Inserted(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadListBoxEventArgs) Handles RadListBoxServiceContacts.Inserted
        Session("Avalability") = "Insert"
        Me.lblContactDescription.Text = "Select a contact to view details"
        Me.lblContactDetails.Text = ""
    End Sub

    Private Sub RadListBoxContacts_Transferred(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadListBoxTransferredEventArgs) Handles RadListBoxContacts.Transferred

        Dim contactID As String = CStr(e.SourceListBox.SelectedItem.DataKey)
        Dim serviceID As String = CStr(Me.RadListBoxServices.SelectedItem.DataKey)

        If CStr(Session("Avalability")) = "Delete" Then
            objWebService.removeContactFromService(contactID, serviceID)
        ElseIf CStr(Session("Avalability")) = "Insert" Then
            objWebService.addContactToService(contactID, serviceID)
        End If
        Me.RadListBoxContacts.Items.Clear()
        Me.RadListBoxServiceContacts.Items.Clear()

        Me.RadListBoxServiceContacts.DataSource = objWebService.getServicesContacts(CInt(Me.RadListBoxServices.DataKeys.Item(Me.RadListBoxServices.SelectedIndex)))
        Me.RadListBoxServiceContacts.DataBind()

        Me.RadListBoxContacts.DataSource = objWebService.getEmployeeContactsNotInService(CInt(Me.RadListBoxServices.DataKeys.Item(Me.RadListBoxServices.SelectedIndex)), Me.RadComboBoxSelectedEmployee.SelectedValue, "")
        Me.RadListBoxContacts.DataBind()

    End Sub

The last four lines are executed in the Page_Load to initially populate the list boxes

As can be seen above the list boxes are re-bound to the database via a web service every time an item is inserted or deleted.

Any help or pointes in the right direction would be great.

Many Thanks.

[Genady Sergeev]

Hello DGraham,

The Transferred event fires when an item is already transferred. This means that the item is removed from the source and is added to the destination. Then the next item in the source is selected so that you can proceed with the transfer. However, when the last item is being transferred, there are no more items to select in the source hence the null reference error. I suggest you to use the e.Items collection to obtain the items being transferred.

Example:

Sub RadListBoxContacts_Transferred(sender As Object, e As RadListBoxTransferredEventArgs)
    Dim item As RadListBoxItem = e.Items(0)
End Sub

I hope this helps.

Kind regards,
Genady Sergeev
the Telerik team

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