Since you are using the approach Aaron suggested, you should create a setter for the visibility for the CellValuePresenter, not the textblock, as you need the whole Cell to be hidden or collapsed like this

<Style x:Key="MyLinkStyle" TargetType="{x:Type igDP:CellValuePresenter}">

<Setter Property="Visibility" Value="Hidden" /> // or Value="Collapsed"

...

</Style>

Alex. 

Playing around, I found the answer - see the line in bold below:

    <Style x:Key="MyLinkStyle" TargetType="{x:Type igDP:CellValuePresenter}">
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="{x:Type igDP:CellValuePresenter}">
            <DockPanel>
              <!-- Give the left edge of the cell a vertical line. -->
              <Border
                    DockPanel.Dock="Left"
                    BorderBrush="#FFEEEEEE"
                    BorderThickness="1,0,0,0"
                    />
              <StackPanel>
                <TextBlock x:Name="tbLink"
                           Text="{Binding Path=DataItem.MyCount}"
                           Tag="{Binding Path=DataItem.MyID}"
                           ToolTip="{Binding Path=DataItem.MyTooltip}"
                           FontSize="11" TextAlignment="Center" Cursor="Hand" ForceCursor="False" Foreground="#FF4731BD" Width="Auto" FontFamily="Arial"
                           PreviewMouseLeftButtonDown="tbLink_PreviewMouseLeftButtonDown">
                                <TextBlock.TextDecorations>
                                    <TextDecoration Location="Underline"/>
                                </TextBlock.TextDecorations>
                </TextBlock>
              </StackPanel>
            </DockPanel>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
      <Setter Property="Visibility" Value="Hidden" />
    </Style>

One last question: I'd like all the links to start out hidden and only show up as the user hovers over each row.  With my current style, the links are all visible until I hover over them, at which point it works as requested.

I tried setting the visibility of the TextBlock to "Hidden" in the style below, but that didn't work.  I need to set the CellValuePresenter's visibility to hidden by default - what do I need to change in the style below to do that?

    <Style x:Key="MyLinkStyle" TargetType="{x:Type igDP:CellValuePresenter}">
      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="{x:Type igDP:CellValuePresenter}">
            <DockPanel>
              <!-- Give the left edge of the cell a vertical line. -->
              <Border
                    DockPanel.Dock="Left"
                    BorderBrush="#FFEEEEEE"
                    BorderThickness="1,0,0,0"
                    />
              <StackPanel>
                <TextBlock x:Name="tbLink"
                           Text="{Binding Path=DataItem.MyCount}"
                           Tag="{Binding Path=DataItem.MyID}"
                           ToolTip="{Binding Path=DataItem.MyTooltip}"
                           FontSize="11" TextAlignment="Center" Cursor="Hand" ForceCursor="False" Foreground="#FF4731BD" Width="Auto" FontFamily="Arial"
                           PreviewMouseLeftButtonDown="tbLink_PreviewMouseLeftButtonDown">
                                <TextBlock.TextDecorations>
                                    <TextDecoration Location="Underline"/>
                                </TextBlock.TextDecorations>
                </TextBlock>
              </StackPanel>
            </DockPanel>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>

Hi Aaron,

That worked, thanks!  For anyone trying this out, here's some sample code:

  Sub New()
    EventManager.RegisterClassHandler(GetType(DataRecordCellArea), DataRecordCellArea.MouseEnterEvent, New MouseEventHandler(AddressOf OnDataRecordCellAreaMouseEnter))
    EventManager.RegisterClassHandler(GetType(DataRecordCellArea), DataRecordCellArea.MouseLeaveEvent, New MouseEventHandler(AddressOf OnDataRecordCellAreaMouseLeave))

    ' This call is required by the Windows Form Designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
  End Sub


  Private Sub OnDataRecordCellAreaMouseEnter(ByVal sender As Object, ByVal e As MouseEventArgs)
    Dim oXamDataGrid As XamDataGrid
    Dim oDataRecordCellArea As DataRecordCellArea

    Try
      oXamDataGrid = TryCast(TryCast(sender, DataRecordCellArea).DataPresenter, XamDataGrid)
      If oXamDataGrid IsNot Nothing AndAlso UCase(oXamDataGrid.Name) = "MYNAMEOFXAMDATAGRIDIFMULTIPLE" Then
        oDataRecordCellArea = TryCast(sender, DataRecordCellArea)
        If oDataRecordCellArea IsNot Nothing Then CellValuePresenter.FromCell(oDataRecordCellArea.Record.Cells("MYFIELDNAME")).Visibility = Visibility.Visible
      End If
    Catch ex As Exception
    End Try
  End Sub

  Private Sub OnDataRecordCellAreaMouseLeave(ByVal sender As Object, ByVal e As MouseEventArgs)
    Dim oXamDataGrid As XamDataGrid
    Dim oDataRecordCellArea As DataRecordCellArea

    Try
      oXamDataGrid = TryCast(TryCast(sender, DataRecordCellArea).DataPresenter, XamDataGrid)
      If oXamDataGrid IsNot Nothing AndAlso UCase(oXamDataGrid.Name) = "MYNAMEOFXAMDATAGRIDIFMULTIPLE" Then
        oDataRecordCellArea = TryCast(sender, DataRecordCellArea)
        If oDataRecordCellArea IsNot Nothing Then CellValuePresenter.FromCell(oDataRecordCellArea.Record.Cells("MYFIELDNAME")).Visibility = Visibility.Hidden
      End If
    Catch ex As Exception
    End Try
  End Sub