How can I dynamically get tooltip using converter? - wpf

Question

If I run my project, my tooltip converter is run once - I need it to run each time the mouse hoover over a row.
Here's my XAML:
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication1"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<local:MyTooltipConverter x:Key="MyTooltipConverter" />
</Window.Resources>
<Grid>
<DataGrid x:Name="dataGrid" ItemsSource="{Binding}" HorizontalAlignment="Left" VerticalAlignment="Top" Height="263" Width="507">
<DataGrid.Resources>
<Style TargetType="{x:Type DataGridRow}">
<Setter Property="ToolTip">
<Setter.Value>
<ToolTip Content="{Binding ??, Converter={StaticResource MyTooltipConverter}}" />
</Setter.Value>
</Setter>
</Style>
</DataGrid.Resources>
</DataGrid>
</Grid>
</Window>
And code...
Imports System.Globalization
Class MainWindow
Public Class Person
Public Property Name As String
End Class
Public Persons As New List(Of Person)
Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
For i As Integer = 0 To 5
Persons.Add(New Person With {.Name = "Test " + i.ToString})
Next
dataGrid.DataContext = Persons
End Sub
End Class
Public Class MyTooltipConverter
Implements IValueConverter
Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.Convert
If value Is Nothing Then
Return Nothing
End If
Dim panel As New StackPanel()
panel.Orientation = Orientation.Vertical
Dim block As New TextBlock()
block.Text = Now.ToString
panel.Children.Add(block)
Dim tip As New ToolTip()
tip.Content = panel
Return tip
End Function
Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.ConvertBack
Throw New NotImplementedException()
End Function
End Class
How can I call MyTooltipConveter af get a Tooltip with the current time?
Thanks

Answer 1

Change your MyTooltipConverter.Convert method to Return panel. Returning tip throws a System.InvalidOperationException - 'ToolTip' cannot have a logical or visual parent.
As for the binding, just using the converter works.
<ToolTip Content="{Binding Converter={StaticResource MyTooltipConverter}}" />
Of course, for the time to update you have to move the mouse around to generate a new tooltip. If what you wanted was to have a tooltip that constantly updates then you need to add a timer and update the block.Text.
Something like this:
Public Class MyTooltipConverter
Implements IValueConverter
Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.Convert
If value Is Nothing Then
Return Nothing
End If
Dim panel = New StackPanel()
panel.Orientation = Orientation.Vertical
Dim block As New TextBlock()
block.Text = Now.ToString
panel.Children.Add(block)
Dim timer As New System.Windows.Threading.DispatcherTimer()
timer.Interval = New TimeSpan(0, 0, 1)
AddHandler timer.Tick, Sub()
block.Text = Now.ToString
End Sub
timer.Start()
Debug.WriteLine("Timer Started")
AddHandler panel.Unloaded, Sub(s, e)
timer.Stop()
timer = Nothing
panel = Nothing
Debug.WriteLine("Timer Stopped")
End Sub
Return panel
End Function
Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.ConvertBack
Throw New NotImplementedException()
End Function
End Class