Bind a property to an existing Binding - wpf

Question

I have an interface with multiple buttons. I'd like to enable or disable these buttons according to a 'complex' condition. I declared this MultiBinding as an application resource in order to avoid code repetition:
<MultiBinding x:Key="MyMultiBinding" Converter="{StaticResource ResourceKey=MyConverter}">
<Binding Path="IsConnected" />
<Binding Path="IsOpened" />
</MultiBinding>
Here is how I declare my button:
<Button Name="MyButton" Content="Click me!" IsEnabled="{StaticResource ResourceKey=MyMultiBinding}" />
At runtime, I get the following error: "Set property IsEnabled threw an exception... MultiBinding is not a valid value for property IsEnabled".
I can't figure why this is not working. Could you please point me to the right way to do this? Thank you.

Answer 1

You can't set the boolean IsEnabled property to a value of type MultiBinding. That is what is happening.
As #Viv pointed out, you could declare a Style to do the heavy lifting:
<Style x:Key="ButtonStyle" TargetType="{x:Type Button}">
<Setter Property="IsEnabled">
<Setter.Value>
<MultiBinding Converter="{StaticResource ResourceKey=MyConverter}">
<Binding Path="IsConnected" />
<Binding Path="IsOpened" />
</MultiBinding>
</Setter.Value>
</Setter>
</Style>
<Button Name="MyButton" Content="Click me!" Style="{StaticResource ButtonStyle}" />
This works well if the Button DataContext has those properties. It works especially well if they each have a different DataContext they are bound to, enabling them for different reasons.
If they are all bound to the same DataContext, or the properties are on a different object, you could use the Freezable Trick to provide a value that your buttons would bind to:
<BindingProxy x:Key="isEnabled">
<BindingProxy.Data>
<MultiBinding Converter="{StaticResource ResourceKey=MyConverter}">
<Binding Path="IsConnected" />
<Binding Path="IsOpened" />
</MultiBinding>
</BindingProxy.Data>
</BindingProxy>
<Button Name="MyButton" Content="Click me!" IsEnabled="{Binding Data, Source={StaticResource isEnabled}}" />

Answer 2

I don't know if this is the best solution, but wrapping the MultiBinding into a style, as Viv said, did the trick. Here is the code of the Style :
<Style x:Key="MyStyle" TargetType="Button">
<Style.Setters>
<Setter Property="IsEnabled">
<Setter.Value>
<MultiBinding Converter="{StaticResource ResourceKey=MyConverter}">
<Binding Path="IsConnected" />
<Binding Path="IsDataAccessOpened" />
</MultiBinding>
</Setter.Value>
</Setter>
</Style.Setters>
</Style>
And the code of the button :
<Button Name="MyButton" Content="Click me!" Style={StaticResource ResourceKey=MyStyle} />