Question

I have a silverlight listbox that is being used as a search result box. I’m using dynamic searching (keyups in the search box cause the events to fire to filter this list box’s contents). The issue I’m running into is if the user scrolls down when the box is unfiltered, then does the search, the rebinding of the listbox does not cause the scroll to go back up to the top making the results look like there is only one value in it.

the code I have so far for the listbox is this (This is a simplified version):

XAML:

<Grid x:Name="MainGrid" Rows="2">
    <StackPanel Orientation="Horizontal" Grid.Row="0">
         <TextBlock text="Search" Grid.Row="0" />
         <Textbox x:name="textboxSearch" Keyup="textBoxSearch_KeyUp" width="200" 
                  Height="25"/>
    </StackPanel>
    <ListBox x:Name="SearchResultBox" Visibility="Visible" Grid.Row="1"
             ScrollViewer.HorizontalScrollBarVisibility="Auto"
             ScrollViewer.VerticalscrollbarVisibility="Auto">
         <ListBox.ItemTemplate>
              <DataTemplate>
                   <StackPanel Orientation="Vertical">
                        <TextBlock Text="{Binding ReportName}" />
                        <TextBlock Text="{Binding ReportDescription}" />
                   </StackPanel>
              </DataTemplate>
         </Listbox.ItemTemplate>
    </ListBox>
</Grid>

VB:

Imports System.Threading
Imports System.Collections.ObjectModel
Imports System.ComponentModel
Partial Public Class ucSearch
     Inherits UserControl
     Private WithEvents BGwork As New BackgroundWorker()
     Private mReportList as New List(Of cFilter)

     Public Sub New()
          InitializeComponent()
          FillReportList()
          NewFilterList()
     End Sub

     Private Sub FillReportList()
          mReportList.Add(new cFilter("Report A", "Report A desc")
          mReportList.Add(new cFilter("Report B", "Report B desc")
          mReportList.Add(new cFilter("Report C", "Report C desc")
          mReportList.Add(new cFilter("Report D", "Report D desc")
          mReportList.Add(new cFilter("Report E", "Report E desc")
          mReportList.Add(new cFilter("Report F", "Report F desc")
          mReportList.Add(new cFilter("Report G", "Report G desc")
          mReportList.Add(new cFilter("Report H", "Report H desc")
          mReportList.Add(new cFilter("Report I", "Report I desc")
          mReportList.Add(new cFilter("Report J", "Report J desc")
          mReportList.Add(new cFilter("Report K", "Report K desc")
          mReportList.Add(new cFilter("Report L", "Report L desc")
          mReportList.Add(new cFilter("Report M", "Report M desc")
     End Sub

     Private Sub textboxSearch_KeyUp(ByVal sender as System.Object, _
                                     ByVal e as System.Windows.Input.KeyeventArgs)
         NewFilterList()
     End Sub

     Private Sub NewFilterList()
          If BGwork.IsBusy Then
               If Not BGWork.cancellationPending Then BGwork.CancelAsync()
               Exit Sub
          End If

          With BGwork
               .WorkerSupportsCancellation = True
               .RunWorkerAsync(textboxSearch.Text)
          End With
     End Sub

     Private Sub BGwork_DoWork(ByVal sender as Object, _
                               ByVal e as System.ComponentModel.DoWorkEventArgs) _
                               Handles BGwork.DoWork
          Dim Filtered as New List(of cFilter)
          If textboxSearch.Text.Length > 0
               dim q = FROM ri In mReportList Where ri.Reportname.ToLower.contains(textboxSearch.Text.ToLower) Select ri
               Filtered = q
          Else
               Filtered = mReportList
          End If
          Dim RTN as List(Of cFilter) = Filtered
          e.Cancel = False
          e.Result = RTN
     End Sub

     Private Sub BGwork_RunWorkerCompleted(ByVal sender As Object_
                                           ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) _
                                           Handles BGwork.RunWorkerCompleted
          If e.Cancelled Then
               NewFilterList()
               Exit Sub
          End If

          Dim RTN as cFilter = TryCast(e.Result, cFilter)
          If IsNothing(RTN) Then Exit Sub

          SearchResultBox.ItemsSource = RTN
          SearchResultBox.InvalidateArrange()
     End Sub
 End Class

 Public Class cFilter
      Inherits BaseDataClass
      Private mReportName as String = ""
      Private mReportDescription as String = ""

      Public Sub New()
           mReportName = ""
           mReportDescription = ""
      End Sub

      Public Sub New(ByVal reportName as String, ByVal reportDescription as String)
           mReportName = reportName
           mReportDescription = reportDescription
      End Sub

      Public Property ReportName() as String
           Get
                Return mReportName
           End Get
           Set(ByVal value as String)
                mReportName = value
           End Set
      End Property

      Public Property ReportDescription() as String
           Get
                Return mReportDescription
           End Get
           Set(ByVal value as String)
                mReportDescription = value
           End Set
      End Property
 End Class

Again this is simplified greatly from what is going on (I go to database to get report names, etc). When I rebind the listbox, how do I get it to scroll all the way to have the first item at the top of the list? Since I don’t have access to the scrollviewer control from within the ListBox object, do I have to make a scrollviewer control that surrounds the listbox and then set where it’s view is from there?

Answer 1

After looking at this post

Automatic Scrolling in a Silverlight List Box

I tried the following and it worked fine for me.

 theListBox.ItemsSource = data;
 theListBox.UpdateLayout();
 theListBox.ScrollIntoView(theListBox.Items[0]);