Databinding a F# viewmodel

Question

From the XAML editor, I can set the namespace to the Viewmodel contained in a C# project ``` namespace ViewModelDB { public class DependencyViewModel : IViewModelDB { public string Message { get; set; } } } ``` And in my xaml ``` ``` The binding "Message" is then recognized. When I point at a F# namespace of similar constituency ``` namespace ModuleDBGraph open Infrastructure open Microsoft.Practices.Prism.Regions; open Microsoft.Practices.Unity;…

Accepted Answer

I don't think there is a better solution than the one we discussed in comments, so I'm turning that into a longer answer.

The reason why it does not work is - as you already suggested - that F# implements interfaces explicitly and so WPF does not see the `Message` property when it is an interface member. The most direct workaround is to define it as an explicit property (and the interface implementation can just refer to the main property):

```
type DependencyViewModel () = 
    member val Message = "" with get, set
    interface IDependencyViewModel with 
        member x.Message with get() = x.Message and set(v) = x.Message <- v
```

In general, I think the patterns recommended for C# do not always work nicely in F#. For example, because F# is more succinct (making things easier to rewrite) and less error-prone (catching more bugs statically), I think you might not actually need an interface in this case at all.

A more complicated workaround would be to generate an implicit implementation of the interface using reflection at runtime (from the explicit implementation) and then set it as `DataContext` but that would not work nicely with editors, so maybe that's not a good direction.

Databinding a F# viewmodel

Solution

Problem