I have a WPF ResourceDictionary with the following TextBlock:

<TextBlock Visibility="{Binding Converter={StaticResource MyBoolProp ResourceKey=BoolToVis}}">
</TextBlock>

The ResourceDictionary is included in App.xaml under MergedDictionaries:

<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="MyResourceDictionary.xaml"/>

Within the App.xaml I have defined the BoolToVis converter (again, under Application.Resources)

<BooleanToVisibilityConverter x:Key="BoolToVis" />

When I start my app up - I get the following XamlParseException:

"Provide value on 'System.Windows.Markup.StaticResourceHolder' threw an exception."

The InnerException is:

"Cannot find resource named 'BoolToVis'. Resource names are case sensitive."

I'm able to refer to this converter directly with App.xaml (in fact, the particular XAML declaration is identical) and within other UserControls with no problems.

This particular bit of code also worked fine under the .NET 4.0 RC (and Beta2). This error only started happening when I upgraded to the .NET 4.0 RTM.

I'm able to work around it by declaring another BooleanToVisibilityConverter within MyResourceDictionary.xaml and referring to it like so:

<TextBlock Visibility="{Binding Converter={StaticResource MyBoolProp ResourceKey=BoolToVis2}}">
</TextBlock>

Any reason why I should need to do this?