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Passing incorrect values into MultiValueConverter by MultiBinding

I've been trying to implement a dynamic ToolTip (WPF) for RadioButton (the ToolTip switches, when IsEnabled of the RadioButton changes). I wanted to achieve this with a MultiValueConverter, which would be sort of a general Converter, that accepts 3 values - the IsEnabled value, enabled ToolTip and disabled ToolTip in this exact order.
But sadly I have encountered an issue, that I haven't been able to solve yet. Basically when the code reaches the Convert Method, the Array of values is filled with DependencyProperty.UnsetValue items.
What I managed to find while googling was, that the problem is propably caused by having a wrong DataContext as mentioned here WPF MultiBinding in Convertor fails ==> DependencyProperty.UnsetValue , but I feel like I have tried every combination of RelativeSources and DataContexts, that I could come up with and nothing helped.
Here is the sample code of the View:
<window.Resources>
<local:BooleanToStringConverter x:Key="BooleanToStringConverter"/>
</window.Resources>
<Grid>
<RadioButton x:Name="RadioButton" ToolTipService.ShowOnDisabled="True"
IsEnabled="{Binding IsRadioButtonEnabled}" VerticalAlignment="Center" HorizontalAlignment="Center" Content="Radio">
<RadioButton.ToolTip>
<ToolTip>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource BooleanToStringConverter}">
<Binding ElementName="RadioButton" Path="IsEnabled"/>
<Binding RelativeSource="{RelativeSource AncestorType={x:Type local:MainWindow}}" Path="ViewModel.EnabledToolTip"/>
<Binding RelativeSource="{RelativeSource AncestorType={x:Type local:MainWindow}}" Path="ViewModel.DisabledToolTip"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</ToolTip>
</RadioButton.ToolTip>
</RadioButton>
So the result, that I expect from this, is that the correct values will be passed into the Converter (in this case value of IsEnabled and string values of Enabled/Disabled ToolTips).
If anybody has any ideas, I would very much appreciate to hear them :).
Thanks in advance.

I managed to fix this by explicitly setting DataContext on the RadioButton and removing the RelativeSources within the MultiBinding. Though I don't understand why it did not work with the RelativeSources, it works. Here is the code, in case of anyone reading this in the future:
<RadioButton x:Name="RadioButton" ToolTipService.ShowOnDisabled="True"
DataContext="{Binding ViewModel, RelativeSource={RelativeSource AncestorType={x:Type local:MainWindow}}}"
IsEnabled="{Binding IsRadioButtonEnabled}" VerticalAlignment="Center" HorizontalAlignment="Center" Content="Radio">
<RadioButton.ToolTip>
<ToolTip>
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource BooleanToStringConverter}">
<Binding Path="IsRadioButtonEnabled"/>
<Binding Path="EnabledToolTip"/>
<Binding Path="DisabledToolTip"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</ToolTip>
</RadioButton.ToolTip>
</RadioButton>

Label Content Binding

Let's say I have a .resx file with a resource key GroupBoxHeaderCaption and value "SomeString".
Then in my ViewModel I have a string property called Description.
What I want to achieve is this (given the .resx file is referred to with using resx = [...] and the view model is called viewModel):
string.Format("{0}: {1}", resx.GroupBoxHeaderCaption, viewModel.Description)
Is it possible to do this in XAML? I got this, but it's not working:
<GroupBox Margin="4">
<GroupBox.HeaderTemplate>
<DataTemplate>
<Label>
<Label.Content>
<MultiBinding StringFormat="{}{0}: {1}">
<Binding Path="{x:Static my:MyResources.GroupBoxHeaderCaption}" />
<Binding Path="viewModel.Description" />
</MultiBinding>
</Label.Content>
</Label>
</DataTemplate>
</GroupBox.HeaderTemplate>
By not working I mean I get GroupBoxHeaderCaption red-underlined with an error that says:
Invalid member type: expected type is 'PropertyPath', actual type is 'string'.
I know I could write a converter for my viewModel.Description, but is there a way to do this all-XAML?
I get the desired result when I do this:
<GroupBox Margin="4" Header="{Binding viewModel.Description}"
HeaderStringFormat="SomeString: {0}">
I want to fetch the "SomeString:" part from a .resx file.

I've just worked out why you're getting that error. It's because you can't refer to the resource string like that in the Path property of that MultiBinding.
I think that maybe you have to try something like this:
<MultiBinding StringFormat="{}{0}: {1}">
<Binding Path="GroupBoxHeaderCaption" Source="{x:Static my:MyResources}" />
<Binding Path="viewModel.Description" />
</MultiBinding>
Unfortunately, I can't try this out now and I'm not sure if this is the correct syntax, so please come back and let me know if you have further problems.

Implementing IValueConverter to get Name from ID

I have a table column called LOCATION_ID. I want to show the LOCATION_NAME which is located in the LOCATION table instead of the ID.
I am trying to implement IValueConverter but can't figure out how to do it. I am using WPF with entity framework.
How would I pass the ID value to this converter?
I have a method name GetLocationNameByID(). Where in the converter would I Call this method? And how would I bind the return value to the datagrid XAML?

Implementing the IValueConverer interface is pretty straightforward. In the XAML, you'd have something like this:
<Window x:Class="CarSystem.CustomControls.AlarmDisplayer"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MyNameSpace"
DataContext="{Binding Path=MyDataContextObject, RelativeSource={RelativeSource Self}">
<Window.Resources>
<local:MyIValueConverter x:Key="Converter" />
</Window.Resoures>
<TextBox Text="{Binding Converter={StaticResource Converter} Path=MyProperty}" />
</Window>
When WPF detects a change in the value of the MyProperty in the MyDataContextObject, it calls the MyIValueConverter object's Convert method, passing the value of the property as the Value parameter. Your implementation of the Convert method does what it has to do & returns the string to be displayed.

you can use multi-binding, have your value converter implement the IMultiValueConverter interface. The converter takes an object array, each of which can be a binding to your XAML.
<TextBox>
<TextBox.Text>
<MultiBinding Converter="{StaticResource MyConverter}">
<MultiBinding.Bindings>
<Binding Path="SomeProperty" />
<Binding RelativeSource="{RelativeSource Self}"/>
</MultiBinding.Bindings>
</MultiBinding>
</TextBox.Text>
</TextBox>

Multibinding using Window's DataContext

I'm trying to create drag adorner based on whether the Customer DependancyProperty of a Window is null. I have this in the Window's resources. The first part of the binding is set (the item being dragged), but the second (the DependancyProperty on the WIndow) shows as UnsetValue.
The property is definitely initialized as it's used as the window's datacontext.
<Window x:Name="root"
...
>
<Window.Resources>
<DataTemplate x:Key="DragAdorner">
<StackPanel Orientation="Horizontal">
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource vehicleDragConverter}">
<Binding/>
<Binding Path="Customer" ElementName="root"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</StackPanel>
</DataTemplate>

customer is not a direct property of element window.
use <Binding Path="DataContext.Customer"..../>
or you can also use RelativeSource=FindControl Window in binding.

Compound DisplayMemberPath for a combobox

I need to create a DisplayMemberPath that is a compound of a few properties (ie object.category.Name+" -> "+object.description) I'm pretty sure I can do this by creating a dynamic data type that encapsulates the object and also adds a new property called displayField that is what I need but I'm wondering if there is a more proper way to do this that does not involve creating a new object. Any ideas?

DisplayMemberPath is just a "shortcut" for when you don't need a complex template for items. If you need more control, use ItemTemplate instead:
<ComboBox ItemsSource="{Binding Items}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock>
<TextBlock.Text>
<MultiBinding StringFormat="{}{0} -> {1}">
<Binding Path="Category.Name" />
<Binding Path="Description" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>