I have a webchart which used to have tooltips working.  There is a 'toggle' for this chart that switches it from being a line chart to a column chart and vice-versa.  Initially I was just simply data binding the chart to a data set - the legend and tooltips were both working.

Yesterday I had to switch from databinding to a data set to creating series then adding them to the chart.  I did not touch any of the settings for the tooltips and for some reason they have disappeared.

I have stopped the code from running just after all the series have been added and can confirm that Chart.Tooltips.FormatString = "<DATA_VALUE>" so it strikes me as odd that the data value isn't actually being picked up anymore.

The chart is contained within a user control.  Here is the markup for the user control:

<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="ChartMain.ascx.vb"
    Inherits="ChartMain" %>
<%@ Register Assembly="Infragistics35.WebUI.UltraWebChart.v8.3" Namespace="Infragistics.WebUI.UltraWebChart"
    TagPrefix="igchart" %>
<%@ Register Assembly="Infragistics35.WebUI.UltraWebChart.v8.3" Namespace="Infragistics.UltraChart.Resources.Appearance"
    TagPrefix="igchartprop" %>
<%@ Register Assembly="Infragistics35.WebUI.UltraWebChart.v8.3" Namespace="Infragistics.UltraChart.Data"
    TagPrefix="igchartdata" %>
<div>
    <asp:Panel ID="MainControlContainer" runat="server">
        <div style="text-align: left; float: left; width: 50px; position: relative; vertical-align: top;">
            <asp:UpdateProgress AssociatedUpdatePanelID="ChartPanel" runat="server" ID="TrendChartProgress">
                <ProgressTemplate>
                    <div style="width: 100%; text-align: left; vertical-align: top; height: 33px;">
                        <asp:Image ID="WindowLoadingAnim" runat="server" ImageUrl="~/Images/windowload.gif" />
                    </div>
                </ProgressTemplate>
            </asp:UpdateProgress>
        </div>
        <div style="text-align: right; float: right; width: 50%; height: 33px; vertical-align: baseline;
            position: relative;">
            <br />
            <asp:ImageButton ID="Settings" runat="server" ImageUrl="~/Images/Gear_32.gif"></asp:ImageButton>
            <asp:ImageButton ID="OpenDetails" runat="server" ImageUrl="~/Images/magnifier.png" />
        </div>
        <asp:UpdatePanel ID="ChartPanel" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="false">
            <ContentTemplate>
                <igchart:UltraChart ID="Chart" runat="server" BorderColor="Black" BorderWidth="0px"
                    ChartType="LineChart" EmptyChartText="Data Not Available." Version="8.3" BackgroundImageFileName="">
                    <Legend BorderThickness="0" Location="Bottom" Visible="True">
                        <Margins Bottom="1" Left="1" Right="1" Top="1" />
                    </Legend>
                    <ColorModel AlphaLevel="150" ColorBegin="SlateGray" ColorEnd="DarkRed" ModelStyle="CustomLinear">
                    </ColorModel>
                    <Axis>
                        <PE ElementType="None" Fill="Cornsilk" />
                        <X LineThickness="1" TickmarkInterval="0" TickmarkStyle="Smart" Visible="True">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="DimGray" HorizontalAlign="Near" ItemFormatString="&lt;ITEM_LABEL&gt;"
                                Orientation="VerticalLeftFacing" VerticalAlign="Center">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="DimGray" FormatString="" HorizontalAlign="Near"
                                    Orientation="VerticalLeftFacing" VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </X>
                        <Y LineThickness="1" TickmarkInterval="100" TickmarkStyle="Smart" Visible="True">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="DimGray" HorizontalAlign="Far" ItemFormatString="&lt;DATA_VALUE:00.##&gt;"
                                Orientation="Horizontal" VerticalAlign="Center">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="DimGray" FormatString="" HorizontalAlign="Far"
                                    Orientation="Horizontal" VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </Y>
                        <Y2 LineThickness="1" TickmarkInterval="100" TickmarkStyle="Smart" Visible="False">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="Gray" HorizontalAlign="Near" ItemFormatString="&lt;DATA_VALUE:00.##&gt;"
                                Orientation="Horizontal" VerticalAlign="Center" Visible="False">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="Gray" FormatString="" HorizontalAlign="Near"
                                    Orientation="Horizontal" VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </Y2>
                        <X2 LineThickness="1" TickmarkInterval="0" TickmarkStyle="Smart" Visible="False">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="Gray" HorizontalAlign="Far" ItemFormatString="&lt;ITEM_LABEL&gt;"
                                Orientation="VerticalLeftFacing" VerticalAlign="Center" Visible="False">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="Gray" FormatString="" HorizontalAlign="Far"
                                    Orientation="VerticalLeftFacing" VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </X2>
                        <Z LineThickness="1" TickmarkInterval="0" TickmarkStyle="Smart" Visible="False">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="DimGray" HorizontalAlign="Near" ItemFormatString="&lt;ITEM_LABEL&gt;"
                                Orientation="Horizontal" VerticalAlign="Center" Visible="False">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="DimGray" HorizontalAlign="Near" Orientation="Horizontal"
                                    VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </Z>
                        <Z2 LineThickness="1" TickmarkInterval="0" TickmarkStyle="Smart" Visible="False">
                            <MajorGridLines AlphaLevel="255" Color="Gainsboro" DrawStyle="Dot" Thickness="1"
                                Visible="True" />
                            <MinorGridLines AlphaLevel="255" Color="LightGray" DrawStyle="Dot" Thickness="1"
                                Visible="False" />
                            <Labels Font="Verdana, 7pt" FontColor="Gray" HorizontalAlign="Near" ItemFormatString=""
                                Orientation="Horizontal" VerticalAlign="Center" Visible="False">
                                <SeriesLabels Font="Verdana, 7pt" FontColor="Gray" HorizontalAlign="Near" Orientation="Horizontal"
                                    VerticalAlign="Center">
                                    <Layout Behavior="Auto">
                                    </Layout>
                                </SeriesLabels>
                                <Layout Behavior="Auto">
                                </Layout>
                            </Labels>
                        </Z2>
                    </Axis>
                    <Effects>
                        <Effects>
                            <igchartprop:GradientEffect />
                        </Effects>
                    </Effects>
                    <Tooltips Font-Bold="False" Font-Italic="False" Font-Overline="False" Font-Strikeout="False"
                        Font-Underline="False" FormatString="&lt;DATA_VALUE&gt;" Display="MouseMove" />
                </igchart:UltraChart>
            </ContentTemplate>
        </asp:UpdatePanel>
    </asp:Panel>
</div>

Here is the code used to generate the series for the line chart:

        Public Function GenerateChartSeries(ByVal itemID As Integer, ByVal seriesType As SeriesType, ByVal seriesLabel As String, ByVal nullHandling As Infragistics.UltraChart.Shared.Styles.NullHandling) As NumericTimeSeries
            Dim addPoint As Boolean
            Dim seriesTypeName As String
            Dim dv As New DataView
            Dim value As Double
            Dim chartSeries As New NumericTimeSeries
            Dim dataPoint As NumericTimeDataPoint

            seriesTypeName = GetSeriesTypeName(seriesType)

            ' If we have data.
            If Not _chartData Is Nothing AndAlso _chartData.Rows.Count > 0 Then
                dv.Table = _chartData

                ' Apply a filter for the specified metric.
                dv.RowFilter = itemID = " & itemID.ToString"

                ' If we have rows in the view after configuring the filter, we must create a series of data points.
                If dv.Count > 0 Then
                    chartSeries.Label = dv.Item(0).Item("ItemName") & ": " & seriesLabel

                    If dv.Table.Rows.Count > 0 Then
                        For index As Integer = 0 To dv.Count - 1
                            addPoint = False

                            If IsDBNull(dv.Item(index).Item(seriesTypeName)) OrElse dv.Item(index).Item(seriesTypeName) Is Nothing Then
                                If nullHandling = Infragistics.UltraChart.Shared.Styles.NullHandling.Zero Then
                                    value = 0
                                    addPoint = True
                                End If
                            Else
                                value = dv.Item(index).Item(seriesTypeName)
                                addPoint = True
                            End If

                            If addPoint Then
                                dataPoint = New NumericTimeDataPoint(dv.Item(index).Item("EventDate"), value, dv.Item(index).Item("EventDate"), True)
                                chartSeries.Points.Add(dataPoint)
                            End If
                        Next
                    End If

                End If
            End If

            Return chartSeries
        End Function

And I'm calling the above code like this (for populating the line chart only):

    Private Sub PopulateChart()
        Dim chartSeries As Infragistics.UltraChart.Resources.Appearance.NumericTimeSeries
        Dim itemIDs As String()

        itemIDs = Me.ItemIDs.Split(",")

        For index As Integer = 0 To itemIDs.Length - 1
                    chartSeries = _chartData.GetChartSeries(CType(itemIDs(index), Integer), SeriesType.Actual, Languages.TranslateText("Actual"), Me._handlingType)

                    If Not chartSeries Is Nothing AndAlso chartSeries.Points.Count > 0 Then
                        Chart.Series.Add(chartSeries)
                    End If
        Next

        If Chart.ChartType = Infragistics.UltraChart.Shared.Styles.ChartType.ColumnChart Then
            Chart.Data.SwapRowsAndColumns = True
        Else
            Chart.Data.SwapRowsAndColumns = False
        End If
    End Sub