Show WPF tooltip on disabled item only

JustABill's suggestion worked. I also needed to define the string as a resource to avoid problems with quotation marks. And you still need to set ToolTipService.ShowOnDisabled="True".

So, here is the working code which shows how to display a tooltip in WPF only when an item is disabled.

In the top container, include the system namespace (see sys below). I also have a Resources namespace, which I called "Res".

    <Window x:Class="MyProjectName.Window1"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:sys="clr-namespace:System;assembly=mscorlib"    xmlns:Res="clr-namespace:MyProjectName.Resources"    >

Then you need

<Window.Resources>    <Res:FalseToStringConverter x:Key="falseToStringConv" />    <sys:String x:Key="stringToShowInTooltip">This item is disabled because...</sys:String></Window.Resources>

In my case, it was a tab item that I was interested in. It could be any UI element though...

<TabItem Name="tabItem2" ToolTipService.ShowOnDisabled="True" ToolTip="{Binding Path=IsEnabled, ElementName=tabItem2, Converter={StaticResource falseToStringConv}, ConverterParameter={StaticResource stringToShowInTooltip}}">            <Label Content="A label in the tab" /></TabItem>

And the converter in code behind (or wherever you want to put it). Note, mine went into the a namespace called Resources, which was declared earlier.

public class FalseToStringConverter : IValueConverter{    #region IValueConverter Members    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)    {        if (value is bool && parameter is string)        {            if ((bool)value == false)                return parameter.ToString();            else return null;        }        else            throw new InvalidOperationException("The value must be a boolean and parameter must be a string");    }    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)    {        throw new NotImplementedException();    }    #endregion}

A little out of date, but I got this working by setting RelativeSource mode to Self instead of setting the ElementName within the Binding.

<TabItem Header="Tab 2" Name="tabItem2" ToolTip="Not enabled in this situation." ToolTipService.ShowOnDisabled="True" ToolTipService.IsEnabled="{Binding Path=IsEnabled, RelativeSource={RelativeSource Mode=Self}, Converter={StaticResource oppositeConverter}}">    <Label Content="Item content goes here" /></TabItem>