If I have a viewmodel property
public (string Mdf, string MdfPath) MachineDefinition { get; set; }
and I try to bind to it in XAML / WPF
The confusion is that for old style Tuple ( pre C#7 ) all the Items were properties
https://msdn.microsoft.com/en-us/library/dd386940(v=vs.110).aspx
and thus bindable. For ValueTuple they are fields
https://github.com/dotnet/runtime/blob/5ee73c3452cae931d6be99e8f6b1cd47d22d69e8/src/libraries/System.Private.CoreLib/src/System/ValueTuple.cs#L269
and not bindable.
If you google "WPF Tuple Binding" you get loads of false positives because old style tuples are bindable but the new ones are not.